Bugs and (mis)features
Table of Contents
If you are going to try and fix any bugs PLEASE READ THE NEXT SECTIONS FIRST. If however you want to jump to a specific year or you have already read the below and you wish to help with a year, you can use these links:
- 1984 entries | 1985 entries | 1986 entries | 1987 entries
- 1988 entries | 1989 entries | 1990 entries | 1991 entries
- 1992 entries | 1993 entries | 1994 entries | 1995 entries
- 1996 entries | 1998 entries | 2000 entries | 2001 entries
- 2004 entries | 2005 entries | 2006 entries | 2011 entries
- 2012 entries | 2013 entries | 2014 entries | 2015 entries
- 2018 entries | 2019 entries | 2020 entries
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PLEASE read the next sections if you wish to help
There are a number of known problems with IOCCC entries: many of which have to do with differences between today’s compiler environments and those of today. In some cases the original code has a bug, some of which were recently discovered and many of which were fixed. In some cases attempt to port older code to more modern environments introduced bugs.
The following is a known list of BUGS and (mis)FEATURES in IOCCC entries.
Can you fix/improve entries not under the INABIAF (it’s not a bug it’s a feature)? You are VERY WELCOME to try.
As far as how to help: please submit your fixes in a GitHub pull request (with ONE PULL REQUEST PER FIX, please)!
We will be happy to credit anyone who submits successful GitHub pull requests in the thanks file. If you’re the author of an entry that win the IOCCC, we will add a link to your winning entries in the file (if you’re not an author, we can add a link to your GitHub page or personal website if you have one, should you wish).
If you do fix an entry please feel free to delete the entry from this file! Otherwise if you wish to not worry about it we can do that to make sure the format is consistent and clean.
THANK YOU!
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To the winning authors:
If you’re the author of an entry that has been fixed and you find it against your liking PLEASE let us know and we’ll be happy to undo any fixes even if it takes away some instructional value or even usability. _In this case we’re VERY SORRY about it: it’s a fine line, we know, and we tried to use careful judgement but invariably some might have been the wrong decision. Thank you for understanding!
When working on getting entries to compile, sometimes some things were changed
that should not have been. Also the definition of INABIAF was changed a number
of times. At one point some things were changed to a bug (a usability problem
for example) to be fixed but when looking at the index.html file it was noticed
it was documented so the fixes were undone at that point.
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ON ALL FIXES / IMPROVEMENTS / CHANGES
Make ABSOLUTE CERTAIN that you test the entry BEFORE AND AFTER your changes! This includes output and the same input functionality! Sometimes it might seem to be fine but is actually not! We will note some where this is known to happen (if it’s not yet fixed). This has actually already happened to us. Sometimes it is okay: some entries are known to not work but they can still have improvements (rarer situation but it’s happened). Some might have slightly different output but which is not a problem for instance a newline after output. This is not the most ideal but it is okay.
Make ABSOLUTE CERTAIN that you read the index.html file BEFORE your changes as it’s important to see that the code is doing what it is supposed to. In the case that it’s not obvious (some index.html files do not even have commands to try or even explain how to use it!) then you should either skip the entry OR ask someone who will know for instance the Judges.
Make ABSOLUTE CERTAIN that you read the next section, the list of statuses and the related information, BEFORE you submit a pull request!
BE VERY AWARE that sometimes fixing an entry for one platform will break it under another so if you have more than one platform (e.g. macOS and linux) it would be wise to test it under all that you have access to. Otherwise we can do that. Of course if the entry does not work under any platform and you fix it for one that’s more than fine (and it has been done numerous times).
Again, THANK YOU!
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LIST OF STATUSES
PLEASE READ BEFORE FIXING
BTW: You may skip if you’re only interested in knowing about entries with known issues.
Entries below have one or more of the following STATUS values. Please see the text below for more information. If an entry has more than one status it means that either they all apply or they complement each other.
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General notes about the statuses and making fixes
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Compiler warnings are very rarely a problem
In general warnings should NOT be addressed. The only time they should be CONSIDERED is when the entry does not work. However note that sometimes trying to fix the warnings will actually introduce bugs! Other times ‘fixing’ them will break the entry (see below).
Below in some entries we do list some warnings that definitely should be ignored (including some introduced by fixes) but we do not list them all: trying to keep track of them all would be impractical especially as different compilers give different warnings.
Another type of warning that would be hard to keep track of is different data
sizes on different platforms. These tend to be required at the risk that
sometimes the entry will not work for certain platforms, some of which might or
might not be fixable; a good example where it was required to change and is okay
is the fix of the segfault in macOS of
1989/paul: changing the int * to a long *
was required and it works just as well with linux.
But even if they are fixable (which will likely be hard to do) it’s almost certain that such code would be just as non-portable (importable ? :-) ).
In rare cases they are valid. For instance in linux the following warning in 1985/applin with gcc:
applin.c:1:78: warning: incompatible implicit declaration of built-in function 'execlp' [-Wbuiltin-declaration-mismatch]
1 | main(v,c)char**c;{for(v[c++]=strdup("Hello, world!\n");(!!c)[*c]&&(v--||--c&&execlp(*c,*c,c[!!c]+!!c,!c));**c=!c)write(!!*c,*c,!!**c);}
| ^~~~~~and this is is kind of like the fix to
1984/anonymous. In the case of 1984/anonymous it
was a bit more involved but with 1985/applin one need only add to the Makefile
-include unistd.h. So there are some cases where fixing warnings can fix a
problem but in general they should be ignored even if they’re annoying.
Hopefully with the example entries listed above you get the idea.
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General request on original code:
If you’re fixing an entry please make as FEW CHANGES AS POSSIBLE! This is to make it as close to the original but allowing it to work. This might be less of a problem when providing alternate versions but it might still be nice to have it as close as possible to the original. See also below two points.
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Request for one-liners:
For one-liners PLEASE KEEP THE FILE ONE LINE IF AT ALL POSSIBLE! See the
guidelines for what constitutes a one-liner. If it needs an
include you can update the Makefile CINCLUDE variable. For instance if it
needs stdio.h you could do -include stdio.h. Please leave a space after the
= in the Makefile. You may also have extra long lines if this seems useful to
make it a one-liner even if it kind of makes it longer than what the judges
consider a one-liner, at least within reason. Thank you!
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On layout of program source:
If you make changes PLEASE TRY AND KEEP THE SOURCE CODE LAYOUT AS CLOSE TO THE ORIGINAL AS POSSIBLE. This might not always be possible and if you have an editor that does formatting it can cause problems. Sometimes formatters can even break code! Some have experienced this many times with vim so he tends to disable all format options when formatting code. In vim you should be able to do that with:
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STATUS: known bug
Please help us fix!
Entries with this status have one or more bugs that need to be fixed. Are you able to fix it? We welcome your help!
An important point to note is that there is a very fine line when fixing bugs where it might sometimes border on tampering with the program. And after all, these are not meant to be maintainable or even good programming style! Use careful judgement when fixing bugs please!
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STATUS: possible bug
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System dependent bug possibly
Please help test, and if necessary fix this bug!
Entries with this status might or might not have a bug possibly depending on the system. In these entries it’s unknown if there is a bug and sometimes it’s because we do not remember and sometimes we don’t have the appropriate system or environment to test and fix any possible problems.
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STATUS: might not be completely functional
Can you confirm there is a bug?
Although these entries appear to work for one or more reasons we’re unsure if they are completely functional. Can you confirm this? Please let us know so we can fix it!
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STATUS: probable bug
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Possible system dependent bug
Please help test and if necessary fix this bug!
Entries with this status almost certainly have a bug or some other problem. The issue or issues might depend on the system much like the above STATUS: possible bug (possibly depending on system).
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STATUS: doesn’t work with some platforms
Please help us fix this bug!
Entries with this status do not work under some OSes and/or architectures (and/or something else?). Please help us to fix it!
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STATUS: doesn’t work with some compilers
Please provide alternative code or fix for more compilers!
Some entries do not work with some compilers. A good example is 1992/lush which uses error messages from the compiler to generate its output.
If you can provide code that works for multiple compilers without too much tampering this is okay though it’s probably not possible with the above mentioned entry; otherwise it would be better to provide alternate code. In some cases it might be better to provide alternate code anyway. Use a judgement call here as best you can manage.
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STATUS: main() function args not allowed
Please help us fix the main() function!
NOTE: it appears that most if not all of these have been fixed except perhaps for 1989/westley but this has probably been fixed as much as possible given the nature of how it generates code: the entry itself compiles but two versions of code it generates does not work with clang.
However some still might have problems of some kind or another and some might
not yet be located as an additional defect of clang was noticed where main()
is not allowed four args or one arg (see below).
This is what the status means, however.
Entries with this status have a problem in that the args to main() are not of a
specific type or there are too many due to this being allowed in earlier C. Some
compilers like clang have a defect where they do not allow this and some
versions have an additional defect where they only allow 0, 2 or 3 args, the
latter of which affected 1989/westley, so these entries do not work with
clang.
Looking at the source
code of clang, it appears that there is no way to override the requirement of
arg types so these entries will fail to compile with clang. That’s why in some
entries the fix was done with a new function, often called pain() :-)
NOTE for macOS users: please be aware that gcc under macOS is actually
clang despite the fact it might appear to be gcc: no symlink and both gcc and
clang exist but the gcc is clang which you’ll see if you run gcc --version.
A tip and some fix methods: in the older days args to main()
not given a type were implicit ints but when they’re required to be char **
this can cause a problem. In some cases it was possible to use a char * inside
main() (see 1989/tromp/tromp.c and
1986/holloway/holloway.c for two examples though
done slightly differently). In other cases it was possible to dereference the
pointers to be used like an int and other times a cast was necessary. There are
various techniques to get these to compile. In some cases this introduced a
problem but typically if not always that problem exists with compilers that are
less strict.
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STATUS: main() has only one arg
Please help modify so that main() as 2 or 3 args!
Because some versions of clang complain about the number of args of main() and
in particular say (when it has four, for instance) that it’s only allowed to
have 0, 2 or 3 args, numerous entries had a second arg added to main() (if
they only had one). This is in case clang adds further restrictions which is not
impossible especially as it already claims having only one arg is not allowed.
At this time (04 Feb 2024) there is one entry known (it is possible that not all
were checked) that has this problem but it’s not as simple as the others to fix
without breaking it.
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STATUS: compiled executable crashes
Please help us fix this bug!
While such entries can compile, the resulting executable sometimes or always crashes.
NOTE: this does NOT apply to entries under the INABIAF status (though they’re not mutually exclusive in some cases).
REMINDER: if you’re debugging a crash it will be very helpful to have -O0 -g
or if you can -ggdb3 when compiling as that will help with debugging symbols.
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STATUS: uses gets()
Please help us change use of gets() to fgets(), if possible.
Entries with this status use gets() which is unsafe because it has no limit on
the length of the string. Many were fixed but not all.
There’s a very good reason for this change even though it is bordering on tampering entries: in modern systems one will get possibly alarming and certainly annoying warnings during at least one of compiling, linking and execution. In macOS it’s most annoying as it happens during execution (also compilation) with the warning being interspersed with the output of the program, often causing confusing output with the entry. A good example that was fixed is 1990/tbr.
Some important notes on this status with respect to fixing / changing the entries:
In some cases changing the entry to use
fgets()will break the entry and in some cases cause it to crash. Where this is known we will document it.You MUST check the output before and after to make sure that it remains the same. Sometimes the output might not be immediately obviously wrong but is. We will document known examples as we come across them.
gets()does NOT STORE the'\n'butfgets()DOES! This is one of the reasons some of the entries break when changed tofgets(). Some of those have been fixed but there are others that have not been.Just because you don’t see the string
getsin the code does not mean it’s not used. It is after all the International Obfuscated C Code Contest! :-) Sometimes it will be in the Makefile and other times it will be obfuscated in other ways; a good example of that that was fixed is 1991/dds: in this case the string was encrypted. Compilers and linkers tend to warn about its use (and as noted in macOS it also happens at execution) and this is a good way to find entries that use it even if it’s not visible in the code.
NOTE: this status is NOT necessarily mutually exclusive with the INABIAF (it’s not a bug it’s a feature) status. The reason for this is due to warnings during compiling, linking and/or runtime, sometimes causing confusing output (as noted above).
Sometimes getline(3) will work but note that this function also stores the
newline just like fgets(3).
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STATUS: missing file(s)
Please help is by finding missing file(s)!
In these entries one file or multiple files are missing from the repo. In some cases these files can be found on the IOCCC website but in other cases they are entirely absent. In this case you’ll probably have to contact the author (unless you are the author! :-) ).
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STATUS: missing or dead link
Please help is fix missing or dead link(s)!
This is as they sound: a link is either missing or it’s no longer valid. In many cases the Internet Wayback Machine will be very useful but there happens to be numerous links that this is not helpful. In other cases the URL has changed. Some of these have been discovered by the Internet Wayback Machine with the orange status.
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Statuses of Internet Wayback Machine archive:
- Green (3xx): redirect (this has been used to find changes in URL).
- Orange (4xx): not found etc.
- Blue: this is a good link (but note that this doesn’t mean that it’s correct!).
The archive website will tell you if the link was never captured.
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STATUS: INABIAF - please DO NOT fix
INABIAF: It’s not a bug it’s a feature :-)
Entries with this status should NOT be touched (unless they have another status that suggests that that issue can be changed): they are system specific by design or are other things that are not actually bugs or bugs even if they appear to be. Or they might be documented bugs or things that simply are part of the entry. Nonetheless they are noteworthy.
NOTE: the definition of this status changed over time. At one point it was when something was noted by the author, the judges, a consequence of earlier requirements for winning entries or the purpose was to do something that might appear to be buggy. An example of system specific entries:
1984/mullender (see below for a version that works in modern systems) is very system specific and was before system specific winning entries were discouraged. This is an all time personal favourite of Landon Curt Noll. Run the alternate code to understand why this might be (along with how strange the source code is :-) ).
An example where a crash is not a bug: 2019/endoh is supposed to crash. There are others that are also supposed to crash or that are known to segfault but are considered features.
An important note is that if the index.html of the entry has a bug status that says it can be fixed it can be. Otherwise it should not be.
Nonetheless we challenge you to fix these entries for educational/instructional value and/or enjoyment but we kindly request that you DO NOT submit a pull request unless it’s a bug or (mis)feature we would like you to fix!
NOTE: in the case of gets() we’ve fixed some to avoid the warning of the
compiler, linker or even during runtime, depending on the system. In some cases
like 1990/tbr the fix actually prevents confusing output (though that
was not the only fix made in that entry).
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Exception: your own entries
Of course if you’re the author you’re welcome to fix your own entry, prefer your own fix or suggest that they’re fixed!
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List of entries by year, sorted in alphabetical order per year
1984
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1984/decot
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STATUS: INABIAF - please DO NOT fix
Source code: 1984/decot/decot.c
Information: 1984/decot/index.html
The purpose of this program is to print out what looks like a fragment of C code. In particular you should see something like:
$ ./decot
'",x); /*
\without a newline after the \. This is not a bug.
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1984/laman
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STATUS: INABIAF - please DO NOT fix
Source code: 1984/laman/laman.c
Information: 1984/laman/index.html
This program will very likely crash or do something funny without an arg.
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1984/mullender
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STATUS: INABIAF - please DO NOT fix
Source code: 1984/mullender/mullender.c
Information: 1984/mullender/index.html
Although there is an alt version and supplementary program added, that will work in modern systems, if you do not have a VAX-11 or PDP-11 to run the original entry on it will not work. See the index.html for details on the alternate versions.
The file gentab.c which is from the
author’s (or one of them, Mullender) remarks, was fixed for modern systems, at
least as best as can be determined: running the code on the binary itself does
produce a short[] that can compile in modern systems but it will not work.
Before the fix it would fail in some cases and it is possible that in some cases
it might still fail.
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1985
There are no known bugs or (mis)features for entries in 1985.
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1986
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1986/august
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STATUS: INABIAF - please DO NOT fix
Source code: 1986/august/august.c
Information: 1986/august/index.html
This entry is known to segfault after printing its output. It was documented by the judges and shouldn’t be fixed.
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1987
There are no known bugs or (mis)features for entries in 1987.
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1988
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1988/dale
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STATUS: INABIAF - please DO NOT fix
Source code: 1988/dale/dale.c
Information: 1988/dale/index.html
In linux it might happen that despite no error message or message about doing so, the program drops a core file into the directory even though the entry works and does not crash.
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1989
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1989/fubar
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STATUS: INABIAF - please DO NOT fix
Source code: 1989/fubar/fubar.c
Information: 1989/fubar/index.html
If you use either fubar or ouroboros.c (it’s executable, see index.html for
details) with a number < 0 or larger than, say 20, it’s very likely that the
program will turn into an infinite loop trying to compile code and end up with
with syntax errors. As this was documented it is not a bug to be fixed.
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1989/robison
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STATUS: INABIAF - please DO NOT fix
Source code: 1989/robison/robison.c
Information: 1989/robison/index.html
This program will very likely crash or break into tiny bits :-) if you feed it numbers with non-binary digits.
There are also other cases where this can happen for instance using unsupported
operators like /. To see what operators are supported check the source code.
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1989/westley
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STATUS: known bug - please help us fix
Source code: 1989/westley/westley.c
Information: 1989/westley/index.html
With version 2 it sometimes segfaults even with the same input where other times it does not. We don’t believe this is because of the fix that lets some versions be compiled with clang. An example invocation is:
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A useful note on changing/fixing this program
It should be noted that in additional to rot13 names there is code that is the reverse of other code (also with respect to names). See the source file and the index.html (in the author’s remarks) for more details.
Fixing the (mis)feature is likely to be a very difficult challenge especially
without breaking something else which is far more likely (see below tips from).
You are welcome to try and fix it if you can but unless you can get all to
compile with clang AND gcc, which seems unlikely (see below), this
should not be touched further. Nonetheless you are welcome to try and fix it if
you can.
Be aware, however, that even if you can get it to compile with both gcc and
clang, different versions will have errors so that it’s not actually a fix.
For instance it was fixed to work for both clang and gcc but when testing
the fix in fedora linux it failed to even compile!
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Tips:
The reason this is crashing is that the array irk is being accessed way out of
bounds by the int gnat. For instance:
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x0000000000401335 in main (ABBA@entry=<optimized out>, tang@entry=<optimized out>, gnat@entry=<optimized out>, Near@entry=<optimized out>)
at ver2.c:23
23 &&gnat!({)Near,noon,/*krelc*/)<0&&(Near= - irk[-gnat--]-2)))&&main(ABBA,
(gdb) p gnat
$1 = -518733305Jump to: top
Magic of the entry:
The real trouble is that the code is generated and in a complex way or rather ways.
Trying to explain this might be tricky but here is an attempt. The program, when used without any args, will print out what it reads. If one arg is specified it will do a ROT13 of it. If two args are specified it will print out the text backwards (WITHOUT ROT13!). If three args are specified it will do both reversal AND ROT13.
So ver0 is the same as the main program; ver1 is the ROT13 of the code (but
see below); ver2 will reverse the code and ver3 will both reverse and ROT13
the code. But it’s trickier than that as one might expect.
The comments are processed too. Furthermore it happens that the last line becomes the first and the first line becomes the last! Now if you look at the code you’ll see on the first line:
/**//*/};)/**/pain(*//**/tang ,gnat/**//*/,ABBA~,0-0(avnz;)0-0,tang,raeNIn ver0 it’ll be the same but the others are more interesting.
In ver1 you’ll see on the last line:
cnva((vag)NOON&2/*//*\\**/,gnat,tang ,NOON/**//*/(niam/**/);}/*//**/and on the first line:
/**//*/};)/**/cnva(*//**/gnat ,tang/**//*/,NOON~,0-0(niam;)0-0,gnat,enrAObserve that the ROT13 of pain is cnva and the ROT13 of main is znva.
The ROT13 of NOON is ABBA. vag is ROT13 of int, gnat and tang are
ROT13 of each other as well which is the reverse of the original (this is not
because it goes backwards (it doesn’t in this version) but because they are
ROT13 pairs!). main spelt backwards is niam and pain spelt backwards is
niap. Furthermore see the Makefile for other defines that had to be specified
and for ver2 and ver3 (that both work with gcc) one had to be undefined (search
for CDEFINE and -U). These details will be important momentarily.
As far as NOON and ABBA being ROT13 pairs, notice how NOON is not in the
original code but ABBA is; but in other versions it becomes NOON and they
also have abba which the original code does not!
Now notice how the avnz in the first line got changed to niam, its ROT13
value. Notice also how some of these are in comments!
main() is in there somewhere and that had to be changed to call
pain() (see the thanks
file (see the 1989/westley section for details on how as this was
not as straight forward as it is for other entries) as well. Now
if you notice on that line you have in a comment niam. If you
were to change that to niap (pain backwards) that function would
end up as pain() in generated code! That’s assuming that it’s
just the reversal version, of course but ver1 is the ROT13 version.
These facts are bad enough but then you throw in the reverse of it without ROT13 and then another version that has the reversal and ROT13 then you can see it’s nigh impossible to fix if not impossible.
The fix to get it to even compile with clang and then get the first two
(counting the original, ver0) to work was quite hard due to how the comments
in reverse and ROT13 of it all works together, especially allowing all versions
to compile with gcc. The only reason that it doesn’t work completely with clang
is the arg types of main() (see if you can figure out how the change of main()
in westley.c is not carried over to versions 2 and 3!); originally none of
them compiled with clang.
But it was possible to get the ROT13 code to compile with clang but the other versions, reversed as well as ROT13 and reversed code, proved much more problematic. It is now possible to compile (or maybe mostly compile) all versions with clang but on another system and it had syntax errors.
Enjoy! :-)
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1990
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1990/baruch
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STATUS: INABIAF - please DO NOT fix
Source code: 1990/baruch/baruch.c
Information: 1990/baruch/index.html
A point worth considering is that as the number passed into the program gets bigger the number of lines of output gets substantially larger and it takes much more time and resources to run as well. For instance:
$ for n in $(seq 1 18); do echo "$n"; echo "$n" | time "./baruch" | wc -l | sed -E -e 's/[[:space:]]//g'; done
1
3
./baruch 0.00s user 0.00s system 5% cpu 0.115 total
2
1
./baruch 0.00s user 0.00s system 64% cpu 0.004 total
3
1
./baruch 0.00s user 0.00s system 60% cpu 0.003 total
4
11
./baruch 0.00s user 0.00s system 64% cpu 0.003 total
5
61
./baruch 0.00s user 0.00s system 66% cpu 0.003 total
6
29
./baruch 0.00s user 0.00s system 61% cpu 0.003 total
7
321
./baruch 0.00s user 0.00s system 69% cpu 0.002 total
8
829
./baruch 0.00s user 0.00s system 76% cpu 0.003 total
9
3521
./baruch 0.00s user 0.00s system 87% cpu 0.005 total
10
7965
./baruch 0.01s user 0.00s system 95% cpu 0.014 total
11
32161
./baruch 0.05s user 0.00s system 98% cpu 0.053 total
12
184601
./baruch 0.29s user 0.00s system 99% cpu 0.294 total
13
1031969
./baruch 1.78s user 0.00s system 99% cpu 1.794 total
14
5483941
./baruch 11.26s user 0.02s system 99% cpu 11.311 total
15
36466945
./baruch 79.20s user 0.15s system 99% cpu 1:19.72 total
16
251132705
./baruch 592.89s user 0.77s system 99% cpu 9:55.34 total
17
1724671873
./baruch 4535.71s user 5.25s system 99% cpu 1:15:49.76 total
18
12655721857
./baruch 37496.97s user 58.50s system 99% cpu 10:27:48.29 totalThis is a feature, not a bug!
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1990/jaw
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STATUS: known bug - please help us fix
Source code: 1990/jaw/jaw.c
Information: 1990/jaw/index.html
Some issues in this program were fixed and Yusuke
Endoh then provided the btoa script but it appears
there is a bug in this entry. The judges wrote that to test the entry one can
do:
echo "Quartz glyph jocks vend, fix, BMW." | compress | ./btoa | ./jawwhich should apply the identity transformation to a minimal holoalphabetic sentence.
But doing this shows instead:
echo "Quartz glyph jocks vend, fix, BMW." | compress | ./btoa | ./jaw
a얖?)V...?????777??hC??h??-? )SSSSXXX????r?L=???*?-???ppp,,,?R
?j
111-)))? '..F@E
???b111?
..F..F.?n,,,,,L@E$Notice how there’s no newline at the end: that final $ is the prompt.
If one does, however:
echo "Quartz glyph jocks vend, fix, BMW." | compress | ./btoa | ./jaw | ./jawthey will get just
oops
which seems to be an error message (one of the fixes was to make it not use
perror(3) - this fixed something else though it’s no longer known what except
that in macOS if errno is 0 it reports what looks like an error, rather than
success in, say, linux).
The script shark.sh has some issues too in that due to
path not having . (this and maybe some other things were fixed) and tar not
wanting to accept reading from stdin (this in particular) even with the right
options used, seemingly, it has to write to disk the tarball which seems to
defeat the purpose. This would ideally be fixed.
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1990/tbr
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STATUS: INABIAF - please DO NOT fix
Source code: 1990/tbr/tbr.c
Information: 1990/tbr/index.html
The authors provided a list of features in the BUGS section in their remarks.
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1990/theorem
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STATUS: INABIAF - please DO NOT fix
Source code: 1990/theorem/theorem.c
Information: 1990/theorem/index.html
Many bugs that prevented this from working properly (including segfaults) were
fixed but one thing to note is that if you pass two zeroes to theorem_bkp or
fibonacci the program will enter an infinite loop, printing 0 over and over
again; another condition where this occurred was fixed but this one should not
be fixed.
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1990/westley
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STATUS: INABIAF - please DO NOT fix
Source code: 1990/westley/westley.c
Information: 1990/westley/index.html
Although this was fixed to not enter an infinite loop if the arg (converted to a number) is < 0 the lack of an arg check at all was kept in to make it like the original. The reason for the < 0 check is it floods the screen (yes this is indeed inconsistent with some other entries but it is not worth the time spent, maybe, to change it back, especially as it is annoying to have the screen flooded).
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1991
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1991/buzzard
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STATUS: INABIAF - please DO NOT fix
Source code: 1991/buzzard/buzzard.c
Information: 1991/buzzard/index.html
If the maze file cannot be opened, either because the path specified does not exist or because the default (whatever the source file was at compilation time) file does not exist in the directory, this program will very likely crash.
This is a feature, not a bug.
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1991/westley
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STATUS: INABIAF - please DO NOT fix
Source code: 1991/westley/westley.c
Information: 1991/westley/index.html
There is a very simple way to always win. The program doesn’t catch you and as someone called Cody’s late grandmother said to him: ‘it’s not cheating unless you’re caught’. :-)
Please don’t try and fix it as it’s not a bug and was actually documented as a possibility. Can you find out how? There’s also a way to make it so that even when you’re cheating it ends up winning! Can you figure that out as well?
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1992
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1992/adrian
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STATUS: INABIAF - please DO NOT fix
Source code: 1992/adrian/adrian.c
Information: 1992/adrian/index.html
The author stated that if the file cannot be opened then it will print a system error but this is not the case unless it’s showing a fault. This was fixed as part of another problem that was detected.
Also, if some of the programs are not given an arg they will very likely crash
or do something funny. For instance adsleep and adbasename. This is very
simple to fix but the author explicitly noted that this will segfault and it is
that that is the error message.
Another thing is that the code:
printf((W,Y));appears to be wrong because W is a FILE * and Y is a char[] but if one
changes it to use fprintf() on the file (which, incidentally, is opened in
read only mode which is another reason) with the %s specifier it will make
adhead not work: it’ll print nothing at all! So this code should not be
changed either even if it appears to be wrong. Notice too a curious thing: if
you did change it to fprintf(), even if you have the right number of args, you’d
have to remove the outer () pair.
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1992/albert
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STATUS: known bug - please help us fix
Source code: 1992/albert/albert.c
Information: 1992/albert/index.html
Leo Broukhis, before he was an IOCCC judge, sent the IOCCC judges an email:
From: leo at zycad -dot- com (Leo Broukhis)
Date: Tue, 30 Jan 96 17:37:51 PST
To: judges at toad -dot- com
Subject: IOCCC 1992 - a bugDear Judges,
albert.c(even in its fixed form) still has a bug. Although I don’t remember the number that exposed the bug (afair, resulting in coredump) inalbert.orig.cthat has been fixed inalbert.c,I’ve found a number exposing another bug: 10000000001 (that’s 9 0’s). Both albert and albert.orig loop without printing anything, although the first factor is 101 and is usually found in an instant.
A quick debugging session suggests that the problem with this value is that:
if ( ppp->qq!=48 ) return;is never reached because the value is never 48 (it is in other cases but not for the example input). It varies in value at this point. Observe that the next lines of code are:
while ( ppp->qq==48 )
{
printf("%ld\n",qqq-45);
*pp = ppp;
ppp = ppp->p;
}so it is expected that that value is 48, before printing the numbers, but if
it’s not it should not proceed at all, not even to go past that loop. In other
words that loop should always be entered for at least one iteration. The check
for the != 48 is also required.
Perhaps more useful to know is that at this point in the code the code:
if ((((( !(aa=setjmp(ppp->ppp))||aa==aaaaaa )))))appears to be entered because of the return value of setjmp(), not the other
condition.
The alt version does fix the problem but it is not obfuscated and not like the entry itself. Can you fix the actual entry? You are welcome to try and do so.
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1992/gson
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STATUS: uses gets() - change to fgets() if possible
Source code: 1992/gson/gson.c
Information: 1992/gson/index.html
This code uses gets(3) on a buffer size of 256 to read from the dictionary. It
is highly unlikely that a line in a dictionary file will be this long but it
could happen and it would be ideal if the code used fgets(3) instead.
Unfortunately with this entry it’s not as simple due to how gets(3) is used,
which can be described simply as: first m is set to *++p in a for loop where
p is argv. Later m is set to point to h which was of size 256. gets(3)
is called as m = gets(m)) but trying to change it to use fgets(3) breaks the
program.
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STATUS: INABIAF - please DO NOT fix
On the other hand, the author noted the following bugs and limitations:
- There is no error checking.
- Standard input must be seekable, so you can’t pipe the dictionary into
AG. - The input sentence and each line in the dictionary may contain at most 32 distinct letters, and each letter may occur at most 15 times.
- Words in the dictionary may be at most 255 bytes long.
AGcannot handle characters that sign-extend to negative values.- Although
AGworks on both 16-bit and 32-bit machines, the size of the problems it can solve is severely limited on machines that limit the stack size to 64k or less.
… so whether or not the gets(3) should be changed to fgets(3) is up to
debate.
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1992/kivinen
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STATUS: known bug - please help us fix
Source code: 1992/kivinen/kivinen.c
Information: 1992/kivinen/index.html
When you start the program everything starts to move over to the right side and then ends. Yusuke Endoh pointed out that if you click the mouse it takes it back towards the centre.
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1992/lush
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STATUS: doesn’t work with some compilers - please provide alternative code or fix for more compilers
Source code: 1992/lush/lush.c
Information: 1992/lush/index.html
This was fixed but it only properly works with gcc; it was also changed to use
fgets() instead of gets() and a script was provided to run the entry
properly. Nonetheless it will only work with gcc.
Unfortunately due to the way the entry works and the fact that other compilers like clang have different warnings and errors this simply does not work with them.
Some tips:
This entry relies on specific compiler warnings. With gcc it will look something like:
[...]
lush.c: In function 'main':
lush.c:40: warning: "f" redefined
40 | main
|
lush.c:1: note: this is the location of the previous definition
1 | #define gets(_) fgets((_),999,stdin)
|
lush.c:42: warning: "f" redefined
42 | #define f 001:
|
lush.c:40: note: this is the location of the previous definition
40 | main
|
lush.c:44: warning: "f" redefined
44 | #define f 100:
|
lush.c:42: note: this is the location of the previous definition
42 | #define f 001:
|
lush.c:45: warning: "f" redefined
45 | _[i--
|
lush.c:44: note: this is the location of the previous definition
44 | #define f 100:
|
lush.c:46: warning: "f" redefined
46 | #define f 126:
|
lush.c:45: note: this is the location of the previous definition
45 | _[i--
|Now one can use sed to get the warning: line correct but there is more to it
than that. For instance this is what it looks like with clang:
lush.c:40:9: warning: 'f' macro redefined [-Wmacro-redefined]
#define f 001:
^
lush.c:1:9: note: previous definition is here
#define f 000:
^
lush.c:42:9: warning: 'f' macro redefined [-Wmacro-redefined]
#define f 100:
^
lush.c:40:9: note: previous definition is here
#define f 001:
^As you might see the part under the warning: line is different.
The entry is supposed to show warnings and then print:
Hello World.Jump to: top
1992/vern
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STATUS: INABIAF - please DO NOT fix
Source code: 1992/vern/vern.c
Information: 1992/vern/index.html
When your own checkmate is imminent it prints "Har har" but does not exit so
it can ‘rub your nose in defeat’, as the author puts it. You will have to exit
it yourself through ctrl-c or killing it in some other fashion.
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1992/westley
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STATUS: INABIAF - please DO NOT fix
Source code: 1992/westley/westley.c
Information: 1992/westley/index.html
The usability of this program was improved by making it so that as long as the terminal columns is >= 80 it will display properly, rather than having to wrap at 80 columns. However due to the nature of the program if the terminal is < 80 in column width it will not display right. To see the number of columns in your terminal try:
echo $COLUMNSJump to: top
1993
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1993/ant
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STATUS: INABIAF - please DO NOT fix
Source code: 1993/ant/ant.c
Information: 1993/ant/index.html
The author stated that:
The expression
(a*)*compiles but loops forever.There is no check for trailing backslash (
\) in the pattern.There is no check for unbalanced brackets. Omitting a closing bracket will generate a “Pattern too long” error, which is not the real error.
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1993/cmills
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STATUS: known bug - please help us fix
Source code: 1993/cmills/cmills.c
Information: 1993/cmills/index.html
In multiple platforms, both macOS and also linux (in particular a RHEL 9.3 system), this entry just shows a blank screen.
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1993/lmfjyh
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STATUS: INABIAF - please DO NOT fix
Source code: 1993/lmfjyh/lmfjyh.c
Information: 1993/lmfjyh/index.html
This entry relied on a bug in gcc that was fixed with gcc version 2.3.3. This cannot be fixed for modern systems as the bug is long gone.
An alternate version that will work for modern systems, however, does exist. See the index.html file for details.
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1993/rince
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STATUS: INABIAF - please DO NOT fix
Source code: 1993/rince/rince.c
Information: 1993/rince/index.html
Although the code checks if the file can be opened or not, badly formatted files will cause problems. No other checks are performed either.
There is no end of game checking function so you will have to quit the game through ctrl-c or such.
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1993/schnitzi
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STATUS: INABIAF - please DO NOT fix
Source code: 1993/schnitzi/schnitzi.c
Information: 1993/schnitzi/index.html
If the file cannot be opened it will very likely segfault. This should not be fixed except for an exercise to yourself, should you wish to try.
This program uses system(3) so if you provide invalid characters in the
question you might cause an error. For instance don’t do this:
$ ./schnitzi schnitzi.info
This program answers questions about paragraphs
of text posed to it in English. It is written
in C. Mark Schnitzius is the author of this
program.
The Loch Ness monster has been captured. Elvis
is alive. Hostler was a woman. The NASA moon
landings were clearly faked.
? What is foo'?because doing so will result in something like:
sh: -c: line 0: unexpected EOF while looking for matching `''
sh: -c: line 1: syntax error: unexpected end of filewith the program terminating. Other characters will also cause this problem.
Of course if you do something like:
What is 'foo'?it will work fine. This is a feature, not a bug!
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1993/vanb
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STATUS: INABIAF - please DO NOT fix
Source code: 1993/vanb/vanb.c
Information: 1993/vanb/index.html
No spaces are allowed in the expression.
The program does no error checking so erroneous expressions will produce spurious results.
The unary - is an operator so decimal -46 should be entered as -d46 and
not d-46.
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1994
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1994/dodsond2
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STATUS: INABIAF - please DO NOT fix
Source code: 1994/dodsond2/dodsond2.c
Information: 1994/dodsond2/index.html
When you initiate shooting via the s command you immediately lose an arrow
before you choose where to shoot.
Also, when you shoot it will move you to that room so if you end up shooting into a pit room you will end up dying even though you didn’t explicitly move there.
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1994/ldb
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STATUS: INABIAF - please DO NOT fix
Source code: 1994/ldb/ldb.c
Information: 1994/ldb/index.html
This was fixed to compile with modern systems but the entry also used gets(3)
which in some systems would print out a warning along with the output of the
program. Naturally it could also overflow long lines, of which there are many,
though that is more considered a feature, not a bug, as it was documented by the
author.
It was changed to use fgets(3) to prevent the display problem but this introduces
another problem namely that newlines can be printed if the line length < 231.
This seems like a worthy compromise to not have messed up output and although it would be ideal for it to never print a newline (unless that’s the line itself) it might be tampering too much with the entry to fix this problem, as it’s not a real problem and as a one liner it’s already quite long.
See the
FAQ on “gets and fgets”
for more information on the change to fgets(3).
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1994/schnitzi
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STATUS: uses gets() - change to fgets() if possible
Source code: 1994/schnitzi/schnitzi.c
Information: 1994/schnitzi/index.html
NOTE: the generated code of all versions, when fed its own source, will differ even when it works. See the author’s remarks in the index.html for details. Increasing the buffer size and having it, when fed its own source code, generate code that will compile with the same buffer size is difficult: it just uses the original size. This is explained later down.
Getting it to use fgets() is even harder as when fed its own code it will
generate code that cannot even compile let alone use fgets(3).
In both cases, changing the buffer size and changing it to use fgets(3), will
cause compilation errors without other adjustments.
See the below magic for details. Along with the author’s remarks in the
index.html file it might prove possible to get it to use fgets(3).
Here is the magic of how this entry works, to help anyone who wishes to work on this.
You might wish to run the commands:
diff schnitzi.alt.c schnitzi.alt2.c
diff schnitzi.alt2.c schnitzi.alt.cto see how the buffer size and how the gets(3) was changed to use fgets(),
in the two alternate versions. Notice that the fgets(3) version can compile it
just can’t generate compilable code (let alone using fgets(3)) when fed
itself (to reiterate, just changing the call to fgets(3) does not mean it can
compile and there’s a further problem in that fgets(3) retains the newline
whereas gets(3) does not). Nevertheless looking at these commands will be of
help to understand how it works, in case one wishes to try and fix it.
For the alternate versions the other functionality is unaffected.
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The magic of 1994/schnitzi and how it flips text
The problem is getting the generated code to use fgets() (once it even
compiles which was easy to do) and also have the updated buffer size be the
same (which was easy to do too at least in the original version). The generated
output, when changed to fgets() failed to compile and it also used gets(3)
and these are the bugs here.
The buffer size, when using gets() is still the same but as noted above the
original code has had a buffer size increase.
The real problem is with formatting the code. Take a look at the #include <stdio.h>, int r=0,x,y=0 and the interesting comment below it, at the top of
the file.
If you look at each column and go down that column you can see how it spells out the code! For instance the first column looks like:
#
i
n
c
l
u
d
e
<
s
t
d
i
o
.
h
>If you join the lines you end up with:
#include <stdio.h>If you look at column 25 which is the end of the word ‘mh111’ and you go down to
the next row you’ll see a 0 and if you go one row down another 0. This is the
buffer size, 100, for u! The column to the left is the same for the t
variable.
Thus it seems that in order to get the generated output correct one needs to provide the correct input in comments or possibly by rearranging some of the code (this was actually required to make the generated code compile at all when changing the buffer size, see below).
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Important points:
Getting this entry to use fgets(3) is easy but the problem is you’re supposed
to be able to feed the source to the program and the output of that will be
compilable. It however will create compiler errors. So it’s not just changing
the code to get it to use fgets(3)! This was done but
the other part is why that part was rolled back. The buffer size was increased
but that only works on the original source.
To say just how sensitive this entry is: even a space, lack of space or a character, wrong character, lack of character or character in the wrong place can cause a compilation error! Make sure that the output of:
./schnitzi < schnitzi.ccan be compiled and the output of that new program when fed itself can also be compiled!
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1994/shapiro
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STATUS: INABIAF - please DO NOT fix
Source code: 1994/shapiro/shapiro.c
Information: 1994/shapiro/index.html
This program will likely crash if the source code file (by the name of the file that’s compiled) cannot be opened in the directory it is run from.
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Important reminder and a note about the -1 value check for getc():
This code was fixed to not use -1 for the return value of getc(); this is
important because EOF is NOT guaranteed to be -1 but rather any negative
value. On systems where EOF != -1 the program would enter an infinite loop
until the program crashed, by chance reads a -1 or was killed (it is for this
same reason that one should not use EOF for the getopt() functions as they
return -1 when all options are parsed (for details on the definition of EOF
see 7.21 Input/output<stdio.h> subsection 1 of the standard)).
An interesting problem occurred where changing the -1 to EOF caused both
warning: illegal character encoding in string literal and error: source file is not valid UTF-8. But since EOF is simply an int < 0 and making the loop
condition check that the return value is >= 0 does not cause a compilation error
and it functions correctly it will address the systems where EOF != -1 just as
if it checked for != EOF.
Since it works there is no need to fix this except for a challenge to yourself.
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1994/tvr
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STATUS: INABIAF - please DO NOT fix
Source code: 1994/tvr/tvr.c
Information: 1994/tvr/index.html
The judges said the following in their remarks:
The fractally minded may be able to detect that mode 0 does not calculate Mandelbrot/Julian sets correctly. Can you find the bug? Better still, can you fix it without breaking something else?
However, the author stated that this is a feature so this should not be fixed. See also the other bugs the author mentioned that, as documented, are considered features.
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1995
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1995/cdua
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STATUS: INABIAF - please DO NOT fix
Source code: 1995/cdua/cdua.c
Information: 1995/cdua/index.html
This did not originally compile under macOS and after it did compile under macOS, it crashed. These problems were fixed.
It should be noted however that there is a condition where the program will
prompt you to press return again. This was thought to be a bug but looking at
the code it can clearly be seen that if g - a is 0 then the message is
supposed to be printed again and one is supposed to press a key as at that point
it calls getchar() via the pointer m. So this is a feature not a bug.
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1995/leo
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STATUS: known bug - please help us fix
Source code: 1995/leo/leo.c
Information: 1995/leo/index.html
The judges suggested that the following commands should result in output:
./leo 1 | cat - /dev/tty | gs -
./leo 37 80 | cat - /dev/tty | gs -The first one can work if one does instead:
echo "" | ./leo 1 > foo.ps
gs foo.psbut it is supposed to work in the pipeline as is. The second one does not appear to work at all even if one redirects to a file (like the workaround for the first) as it appears to just block.
It is not known if this is platform specific but this was observed in macOS and it would be good if it was fixed.
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1995/savastio
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STATUS: INABIAF - please DO NOT fix
Source code: 1995/savastio/savastio.c
Information: 1995/savastio/index.html
This program expects a POSITIVE number. If you specify a negative number it will not show any output, stuck in a loop.
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1995/vanschnitz
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STATUS: missing file - please provide it
Source code: 1995/vanschnitz/vanschnitz.c
Information: 1995/vanschnitz/index.html
The authors stated that they included a version that allows people with just K&R compilers to use the program but this file is missing. Can you provide it?
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1996
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1996/gandalf
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STATUS: missing or dead link or links - please provide it or them
Source code: 1996/gandalf/gandalf.c
Information: 1996/gandalf/index.html
The link was http://www.tc3.co.uk/~gandalf/G.HTML but this no longer exists as
it was instead requiring a login / password.
Do you have an updated link? We welcome your help!
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1996/huffman
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STATUS: uses gets() - change to fgets() if possible
Source code: 1996/huffman/huffman.c
Information: 1996/huffman/index.html
The changing to using fgets(3) in this entry is a bit more complicated. It can
almost be done except that some of the output of the
try.sh is wrong, especially the last one.
This diff almost does it but not quite:
diff --git i/1996/huffman/huffman.c w/1996/huffman/huffman.c
index a5745bc7f4fa28b834c004f4cf19633e40ad9165..5e5e5334f33f9dbd95c70eddece3189d9bcff5e9 100644
--- i/1996/huffman/huffman.c
+++ w/1996/huffman/huffman.c
@@ -1,15 +1,16 @@
#define x char
#define z else
#define w gets
+#define gets(b) ((b)[0]='\0',(fgets((b), 100, stdin)))
#define r if
#define u int
#define s main
#define v putchar
#define y while
#define t " A?B?K?L?CIF?MSP?E?H?O?R?DJG?NTQ?????U?V?????X???????Z????W??Y??"
- s ( ) { x* c , b[ 5 * 72 ]; u a, e , d [ 9
+ s ( ) { x* c , b[ 5 * 72 ]; u a, e , d [ 9
*9 *9 ] ; y (w ( b) ){ r ( 0 [ b] -7 *
5 ) { c = b ; y ( (* c - 6
* 7 )* * c )c = c+ 1 ; r (( -0 ) [ c ] && w ( b +
8 * 5* 3 ) && w (b +8 *5 * 6) )
{ a = 0; y ( a [ b ]But since it does not for the time being it is advisable to just redirect
stderr to /dev/null (2>/dev/null).
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1996/jonth
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STATUS: INABIAF - please DO NOT fix
Source code: 1996/jonth/jonth.c
Information: 1996/jonth/index.html
If X is not running this program will very likely crash or do something funny. This should NOT be fixed.
NOTE: the two boards will be on top of each other so you will have to drag one off the other so that you can properly play.
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STATUS: missing or dead link or links - please provide it or them
As well: the link which was http://www.uio.no/~jonth is no longer valid and
there’s no archive on the Internet Wayback Machine. Do you know of a proper URL?
We greatly appreciate your help here!
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1997
There was no IOCCC in 1997.
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1998
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1998/chaos
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STATUS: INABIAF - please DO NOT fix
Source code: 1998/chaos/chaos.c
Information: 1998/chaos/index.html
The author stated the following:
Memory
malloc(3)ed is never freed. This shouldn’t be a big deal, since only one block is ever allocated, and the OS should recover it.My local flavor of lint doesn’t seem to like the fact that I never
returnfrommain(). Feh, what does it know? Otherwise, ignoring lint’s over protectiveness (“Of course I’m not using all of the functions defined incurses.h!”), it’s lint clean.If the compiler happens to generate the byte sequence “AlWuzEre” in the executable by chance, the program may be unable to locate the embedded string. As a result, running the program without an external data file may act in undefined ways. If the compiler doesn’t store
char * P’s data in a nice contiguous stream, it would be bad. As above, it would break running the program without an external data file.If the incoming data is corrupt, the results are undefined. (Although dumping core is a popular result.)
When a point passes behind the camera, it is still plotted. The object will “bounce” off the camera, but the result (some points in front, some reflected from the rear) looks really odd. And it sometimes hangs. So just don’t fly through objects. You’ll be happier.
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1998/dlowe
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STATUS: missing or dead link or links - please provide it or them
Source code: 1998/dlowe/dlowe.c
Information: 1998/dlowe/index.html
The domain http://pootpoot.com no longer exists as it once did. The judges have
given a script that can be used to make a similar page (warning: not checked
for security in modern days!). Do you have a server with enough bandwidth and
would like to set it up? We’ll gladly thank you in the thanks
file file and link to the page as well! You’ll also have
IOCCC fame for reviving a pootifier! :-)
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1998/dloweneil
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STATUS: missing or dead link or links - please provide it or them
Source code: 1998/dloweneil/dloweneil.c
Information: 1998/dloweneil/index.html
The domain http://pootpoot.com no longer exists as it once did. The judges have
given a script that can be used to make a similar page (warning: not checked
for security in modern days!). Do you have a server with enough bandwidth and
would like to set it up? We’ll gladly thank you in the thanks
file file and link to the page as well! You’ll also have
IOCCC fame for reviving a pootifier! :-)
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1998/schnitzi
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STATUS: INABIAF - please DO NOT fix
Source code: 1998/schnitzi/schnitzi.c
Information: 1998/schnitzi/index.html
A point worth considering is that as the number passed into the program gets bigger the number of lines of output gets substantially larger. For instance:
$ ./schnitzi 9|wc -l
771999The larger the number the bigger the file can become too, even becoming
gigabytes in size. The range is checked for >0 && <27 as not having this can
be a problem including a segfault.
If you use the generated program and do not give enough numbers in input something funny will happen, very possibly with different results per run. This is in the index.html file as something to try and ponder.
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1999
There was no IOCCC in 1999.
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2000
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2000/dlowe
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STATUS: known bug - please help us fix
Source code: 2000/dlowe/dlowe.c
Information: 2000/dlowe/index.html
The author gives an example command:
echo "7 P 6 d P P 8 p" | ./dlowe | tr 876 tpowhich should print out poot but it doesn’t, not in linux and not in macOS.
In linux it doesn’t crash but it doesn’t print anything out either.
In macOS it crashes; it might appear to not crash in macOS but this is because
of the pipeline. If you remove the | tr 876 tpo part of the command you will
see that it does indeed crash!
The reason for this not working is really strange.
$ echo "7 P 6 d P P 8 p" | ./dlowe
7668
$ echo "7 P 6 d P P 8 p" | ./dlowe | grep 7
$Why? Is it writing to stdout? Let’s try some other things:
$ echo 7668 | tr 876 tpo
pootOkay so we know that it SHOULD work. But we also know something funny is going on with stdout and the entry. Another experiment:
$ echo "7 P 6 d P P 8 p" | ./dlowe 1>&2 | grep 7
7668Okay so now it sees it, grep. But watch!
$ echo "7 P 6 d P P 8 p" | ./dlowe 2>foo 1>&1
7668
$ cat foo.. so it does appear to be writing to stdout but yet somehow it doesn’t? But watch:
$ echo "7 P 6 d P P 8 p" | ./dlowe 1>foo 1>&1
$ cat foo
$Well this explains why the tr does not transliterate it to poot but why is
this happening? Why can’t it be redirected to another file even?
If it could be figured out why it’s not writing to stdout and yet at the same time is writing to stdout one bug could be fixed. Maybe it’s the perl messing with things but we don’t know.
Other commands do work, however, and give the appropriate output, such as:
$ echo 1 2 + p | ./dlowe
3so something is wrong with some commands/operators.
Another feature that does work in linux is:
$ echo poot | ./dlowe
poot was here!Can you help fix these problems?
Here is some C code that creates an unformatted perl script that will just
print ‘unimplemented’ for operators but it seems to work in some other ways (see
below for how to go further than unimplemented) which is the exact perl from the
C program except that it has the #!/usr/bin/env perl and use warnings; as
well. A note below might suggest that doing this creates incomplete perl.
Anyway:
#include <stdio.h>
int main(void)
{
printf("#!/usr/bin/env perl\nuse warnings;_:$_= <> ; defined or exit; @ARGV"
"=split; __:$_= shift;defined or goto _; chomp "
";(m*^\\x70oO" "\\x74$*i)?(pri" "nt \"$_ w\\x"
"61s h\\145r\\x" "65!\\n\"):((m*" "^\\s\\*(-?\\d+"
"(\\.\\d+)?)\\s" "\\*$*)?(push@SS ,$1):(&{chr(((o"
"rd)%%39)+3**4)x2 } )); goto __; sub ff { @SS= ("
")} sub __{print \"stack empty\\" "n\"} sub ss{$#"
"SS<0 and goto & __; print $SS[$" "#SS].\"\\n\"} "
"sub SS{ $#SS<0 and goto &__ ; print pop @SS}"
"sub _ { print \"divide by zer" "o\\n\"}sub ii{"
"map{ print\"$_" "\\n\" } reverse @SS} sub AUTOLO"
"AD { print\"un" "implemented\\n" "\"} sub gg{ $#"
"SS<0 and goto &__;push@SS,$SS[ $#SS]} sub uu{ "
"$#SS<1 and goto &__;$SS[ $#SS]+= $SS[$#SS-1];$SS"
"[$#SS-1]=$SS[$" "#SS]-$SS[$#SS-" "1]; $SS[$#SS]-"
"=$SS[$#SS-1]}");
}Compiling this you can generate:
#!/usr/bin/env perl
use warnings;_:$_= <> ; defined or exit; @ARGV=split; __:$_= shift;defined or goto _; chomp ;(m*^\x70oO\x74$*i)?(print "$_ w\x61s h\145r\x65!\n"):((m*^\s\*(-?\d+(\.\d+)?)\s\*$*)?(push@SS ,$1):(&{chr(((ord)%39)+3**4)x2 } )); goto __; sub ff { @SS= ()} sub __{print "stack empty\n"} sub ss{$#SS<0 and goto & __; print $SS[$#SS]."\n"} sub SS{ $#SS<0 and goto &__ ; print pop @SS}sub _ { print "divide by zero\n"}sub ii{map{ print"$_\n" } reverse @SS} sub AUTOLOAD { print"unimplemented\n"} sub gg{ $#SS<0 and goto &__;push@SS,$SS[ $#SS]} sub uu{ $#SS<1 and goto &__;$SS[ $#SS]+= $SS[$#SS-1];$SS[$#SS-1]=$SS[$#SS]-$SS[$#SS-1]; $SS[$#SS]-=$SS[$#SS-1]}Here is example input/output:
p
stack empty
5 p
5
5 + 5 p
unimplemented
5
P
5
p
5So you can see that if one uses operators it just shows ‘unimplemented’ (observe how this does not happen in the C program in linux!) but if one uses ‘p’ by itself it will print what’s on the stack (for example).
To not get ‘unimplemented’ you can remove from the perl:
sub AUTOLOAD { print"unimplemented\n"}(Note that the author stated this was used for exception handling so another possibility is that the C code doesn’t generate the correct perl and indeed even spaces is known to break the perl in at least one way, syntax errors, but maybe others too.)
Here is an example run of several operations in the perl script after removing that subroutine:
$ echo 5 5 p | ./dlowe.pl
5
$ echo 5 5 + p | ./dlowe.pl
5
Undefined subroutine &main::UU called at ./pl.pl line 2, <> line 1.
$ echo 5 5 * p | ./dlowe.pl
5
Undefined subroutine &main::ww called at ./pl.pl line 2, <> line 1.
$ echo 5 5 - p | ./dlowe.pl
5
Undefined subroutine &main::WW called at ./pl.pl line 2, <> line 1.
$ echo 5 5 / p | ./dlowe.pl
5
Undefined subroutine &main::YY called at ./pl.pl line 2, <> line 1.
$ echo 5 P | ./dlowe.pl
5$ echo p | ./dlowe.pl
stack empty
$ echo P | ./dlowe.pl
stack emptyNote the undefined subroutine error: that happens with commands that are not
even in the program. Again the author used AUTOLOAD for exception handling so
it seems likely that there is something missing (which the below shows as well).
For instance inputting D followed by XX:
Undefined subroutine &main::nn called at ./pl.pl line 2, <> line 6.
Undefined subroutine &main::[[ called at ./pl.pl line 2, <> line 1.That means then that in linux despite the subroutines seemingly not existing it works in the code, at least in some cases.
As far as the unimplemented error goes: the author stated that it means there is invalid input. But as can be seen by the input given, the input is not actually incorrect. It is also curious to note that it ends up printing what’s on the stack at that point:
$ echo 5 5 + p | ./dlowe.pl
unimplemented
5which might (?) suggest that the + operator is unimplemented.
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STATUS: INABIAF - please DO NOT fix
The author states that in perl < 5.6.0 there is a bug with a core dump in what
they said is in Perl_sv_upgrade. As this is documented it is not considered a
bug to be fixed. For the curious this will crash in macOS. It was noted that the
code that crashes is:
perl_eval_sv
(newSVpv("_:$_= <> ; defined or exit; @ARGV"
"=split; __:$_= shift;defined or goto _; chomp "
";(m*^\\x70oO" "\\x74$*i)?(pri" "nt \"$_ w\\x"
"61s h\\145r\\x" "65!\\n\"):((m*" "^\\s\\*(-?\\d+"
"(\\.\\d+)?)\\s" "\\*$*)?(push@SS ,$1):(&{chr(((o"
"rd)%39)+3**4)x2 } )); goto __; sub ff { @SS= ("
")} sub __{print \"stack empty\\" "n\"} sub ss{$#"
"SS<0 and goto & __; print $SS[$" "#SS].\"\\n\"} "
"sub SS{ $#SS<0 and goto &__ ; print pop @SS}"
"sub _ { print \"divide by zer" "o\\n\"}sub ii{"
"map{ print\"$_" "\\n\" } reverse @SS} sub AUTOLO"
"AD { print\"un" "implemented\\n" "\"} sub gg{ $#"
"SS<0 and goto &__;push@SS,$SS[ $#SS]} sub uu{ "
"$#SS<1 and goto &__;$SS[ $#SS]+= $SS[$#SS-1];$SS"
"[$#SS-1]=$SS[$" "#SS]-$SS[$#SS-" "1]; $SS[$#SS]-"
"=$SS[$#SS-1]} ",0),0 );and in particular it appears that it is the perl itself. In other words if one changes it to be:
perl_eval_sv(newSVpv("",0),0);it will not crash. But of course it won’t do anything either. So it’s more
specifically that the call to newSVpv() crashes the code but INSIDE
(key point!) the call to perl_eval_sv() that does it. Given what the author
stated and that the version of perl is < than 5.6.0 which the author states can
crash this makes sense.
The example command above should print:
$ echo "13 14 15 16 17 + - * / p" | ./dlowe
-0.0515873015873016and that’s what it shows in linux.
Note that with different perl libraries in macOS (for instance from Homebrew and MacPorts package managers) it will likely print different warnings when compiling. It was observed that with Homebrew it does not report any warnings but with MacPorts it results in a total of 92 warnings! Nonetheless neither works okay and both crash.
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STATUS: INABIAF - please DO NOT fix
Source code: 2000/primenum/primenum.c
Information: 2000/primenum/index.html
This program does not do what you might think it does! Running it like:
./primenum 13will seemingly wait for input exactly because it is waiting for input. See the index.html file or look at the source.
Although the name of the program suggests it prints prime numbers this is not the case. This is by design. See the author’s comments for more details or better yet look at the code and if necessary try it out. Please do not try and fix this.
A crash in the program is known as well. This is also a feature. Please do not try to fix the crashing of this code except to challenge yourself (if you think that it’ll be worth your two second fix :-) ). If you do fix it please do not make a pull request.
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2000/rince
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STATUS: INABIAF - please DO NOT fix
Source code: 2000/rince/rince.c
Information: 2000/rince/index.html
If DISPLAY is not set the program will very likely crash, do something strange
(or if you’re very unlucky your computer might halt and catch
fire! :-) ).
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2001
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2001/anonymous
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STATUS: INABIAF - please DO NOT fix
Source code: 2001/anonymous/anonymous.c
Information: 2001/anonymous/index.html
This was fixed so that it doesn’t segfault and then also fixed the functionality of it (but see below).
The anonymous.ten.c program was
also fixed (it also segfaulted) but note that it MUST be compiled as a 32-bit ELF
binary so it will NOT work in macOS (for example); if you cannot use -m32 or
even if you can but it cannot compile as an ELF binary (not elf binary :-) )
(but see below) then the anonymous program itself will very likely crash if
you run it on the compiled
anonymous.ten.c; if nothing else
it will not modify the target executable (this part of the fix at least should
be correct).
Note also that if you don’t specify a file or you specify a non-32-bit ELF file this program will very likely crash or do something strange like slaughter the Elves of Imladris :-(
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2001/bellard
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STATUS: INABIAF - please DO NOT fix
Source code: 2001/bellard/bellard.c
Information: 2001/bellard/index.html
The author stated that it only works with i386 linux so the fact it doesn’t work in modern systems is considered a feature and not a bug.
An initial segfault was fixed (trying to open the file) and the supplementary program bellard.otccex.c was also fixed but this still crashes in systems not i386 linux which is what the author stated.
The author said that they compiled it with gcc version 2.95.2. We don’t know if a certain gcc version is necessary but it might be helpful to download and compile that version to test it - or it might not.
Yusuke was able to get this to work with -m32 but only in an emulator. As
such, it might be that the changes made should be rolled back but at least now
the supplementary program will work in modern systems.
On the author’s web page for this program it is explicitly stated that it requires i386 linux.
There it was found what should be a more portable version which is included as
otccelf.c (after adding some #includes
and the modification but it appears this also requires i386 linux; indeed
looking at the code it hard codes paths that are i386 specific to linux.
Another point of interest is that the author provided unobfuscated versions which might be of value to look at.
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Aside: why were there changes made if INABIAF ?
This is a good question. The reason is we believe it better to fix some obvious problems: there were some bugs that would very possibly prevent it from working even if it was in i386 linux though it did seem to work in an emulator, so perhaps not. Still it’s better to have the type of the file pointer correct and so that the file can at least be opened in modern systems even if the compiler won’t work there.
Also the supplementary program, which did not work at all, was fixed and it can be run by itself for fun in modern systems, which was not possible before the fixes there.
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2001/cheong
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STATUS: INABIAF - please DO NOT fix
Source code: 2001/cheong/cheong.c
Information: 2001/cheong/index.html
This program will crash without an arg.
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2001/dgbeards
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STATUS: INABIAF - please DO NOT fix
Source code: 2001/dgbeards/dgbeards.c
Information: 2001/dgbeards/index.html
This program deliberately crashes if it loses (which is what it aims to do).
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2001/herrmann1
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STATUS: known bug - please help us fix
During compilation you’re supposed to see some animation but this does not seem to work with modern gcc versions. It appears that version 2.95 works but maybe others do as well. If you have a fix for modern versions of gcc, your help is welcome.
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2001/kev
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STATUS: INABIAF - please DO NOT fix
Source code: 2001/kev/kev.c
Information: 2001/kev/index.html
Sometimes when one player presses q it will result in broken pipe on the other
end.
The author also noted that some versions of curses have problems with
getch() having a delay.
The program is very likely to segfault if the specified port can’t be bound or connected to.
If the terminal is too wide (the author suggests over 500 characters) the program can segfault.
It’s also possible to crash the program if a player scores over a billion points.
Although it is independent of endianness both systems need the same character set. In other words both have to be ASCII or EBCDIC - not one of each.
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2001/ollinger
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STATUS: INABIAF - please DO NOT fix
Source code: 2001/ollinger/ollinger.c
Information: 2001/ollinger/index.html
This program will very likely crash or do something unexpected if you do not provide enough args.
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2001/rosten
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STATUS: INABIAF - please DO NOT fix
Source code: 2001/rosten/rosten.c
Information: 2001/rosten/index.html
See list of bugs here.
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2001/schweikh
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STATUS: INABIAF - please DO NOT fix
Source code: 2001/schweikh/schweikh.c
Information: 2001/schweikh/index.html
The glob pattern must match the whole string. See the author’s comments for details and a workaround.
There’s also no way to escape meta characters.
See also the author’s list of bugs here.
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2001/westley
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STATUS: uses gets() - change to fgets() if possible
Source code: 2001/westley/westley.c
Information: 2001/westley/index.html
This function uses gets(3) but it would be ideal if it used fgets(3). This
one is rather complicated but you are welcome to try and fix this if you wish.
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STATUS: main() has only one arg - try and make it have 2 or 3
This program only has one arg to main(). However changing it to have 2 is not
as simple as it might seem. Doing this breaks things. If memory serves changing
it to two will, for instance, break the punch card code output. It might be that
that is for fgets(3), however, but the point remains: in order to test any
fixes you must determine if the extra files generated (some from sort(1)) -
see the index.html file - generate correct output as well as that the main entry
does too. You might try running the try.sh script and redirect it to a file
first so that you can compare the output. Make sure to recreate the extra files
as described by the author if you do fix this. This might be looked at later if
nobody else takes up the challenge.
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2001/williams
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STATUS: known bug - please help us fix
Source code: 2001/williams/williams.c
Information: 2001/williams/index.html
There seem to be a couple bugs at least in this entry. The first one is that
when it does reach a certain point it crashes. This is in the function J() (or
one it calls?). But sometimes it seems to not get that far, just showing lines
moving back and forth. This is also in J(). It is not confirmed but it might
be that the lines are drawn by XDrawString(), the last part in J().
J() has a for loop identified by for and also a couple while loops,
identified by R.
Since the game never ends properly the score is not printed either.
It appears that the crash happens in more than one place. For instance it has happened at
XCheckMaskEvent(d, 4,&e)but it’s also happened at
else XDrawPoint(d ,w,g,(l.s+=l.a)>>9, h=(l.c+=l.b)>>9)In both cases the pointer d was corrupted:
(lldb) p d
(Display *) 0x0000000000000001It is believed that it also happened at
XDrawString(d,w,g,W/3,H/2,m,B);in J() and for the same reason.
The loop seems to be stuck in the call to usleep(3) like:
usleep(p*200);which happens to be in a while() loop.
There is a way to get the code to crash. If you don’t do anything until everything is destroyed (where you’d lose the game if it ended) and then you start to shoot your missiles repeatedly it will eventually crash. It appears not to be the case (though this was not tried as many times) if you start shooting when the missiles come down. The fact you can shoot after it starts that sleeping in a loop does suggest that it’s not stuck only showing those lines and sleeping.
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2002
There was no IOCCC in 2002.
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2003
There was no IOCCC in 2003.
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2004
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2004/gavin
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STATUS: INABIAF - please DO NOT fix
Source code: 2004/gavin/gavin.c
Information: 2004/gavin//index.html
This program is x86 linux specific; it is extremely likely that a segmentation fault will occur in other systems but even if it does not it is highly unlikely it will work. Below we will give some examples as well as a change that was made to let it compile with clang.
In macOS with the arm64 chip this will segfault:
./gavin > kernelWhen trying to link gavin.o to produce sh, the linker generates:
Undefined symbols for architecture arm64:
"start", referenced from:
-u command line option
(maybe you meant: __start)
ld: symbol(s) not found for architecture arm64Jump to: top
Recent 2004/gavin mods:
Although not related some recent changes were made to 2004/gavin to let it compile under clang. The following patch was applied:
diff --git a/2004/gavin/gavin.c b/2004/gavin/gavin.c
index c967b7e..2082b49 100644
--- a/2004/gavin/gavin.c
+++ b/2004/gavin/gavin.c
@@ -1,8 +1,9 @@
+int main(int t, char **q, char **d) { return cain(t, (int)q, (int)d); }
#define G(n) int n(int t, int q, int d)
#define X(p,t,s) (p>=t&&p<(t+s)&&(p-(t)&1023)<(s&1023))
#define U(m) *((signed char *)(m))
#define F if(!--q){
-#define I(s) (int)main-(int)s
+#define I(s) (int)cain-(int)s
#define P(s,c,k) for(h=0; h>>14==0; h+=129)Y(16*c+h/1024+Y(V+36))&128>>(h&7)?U(s+(h&15367))=k:k
G (B)
@@ -52,7 +53,7 @@ else
G (_);
G (o);
-G (main)
+G (cain)
{
Z, k = K;
if (!t)The original Makefile from 2004 had the following to say about this entry:
# Special flags for the gavin entry
#
# FYI: Older versions of GCC have a bug in -O2 optimization, hence -O1
#
GAVIN_OPT= -O1
GAVIN_FLAGS=\
'-DY(m)=*((int*)(m))'\
'-DE(f,a,b,c)=((G((*)))(f))(a,b,c)'\
'-DM=for(D=0;D<786432;D++)'\
'-DZ=int i=0,j=0,h,n,p=393728,s=26739,C,D'\
'-DV=0x90200'\
'-DK=0'\
'-DR=while((C=E(V-8,100,0,0))&3&&(D=E(V-8,96,0,0))|3){'\
'-DL(c,d)=E(V+8,100,c,0);R}E(V+8,96,d,0);R}'
# ...
# Best of Show
#
gavin: gavin.c
${CC} ${GAVIN_OPT} -o gavin ${GAVIN_FLAGS} gavin.c
${RM} -f kernel
./gavin > kernel
${CC} ${GAVIN_OPT} -c ${GAVIN_FLAGS} -DB=_start '-Dputchar(a)=' gavin.c
${RM} -f sh
${LD} -s -o sh gavin.o
${RM} -f vi
${CP} sh vi
${RM} -f fs.tar
${TAR} -cvf fs.tar sh vi gavin.c index.html prim
gavin_clean:
${RM} -f sh vi kernel gavin.o
gavin_clobber: gavin_clean
${RM} -f gavin fs.tar
gavin_files: boot.b lilo.conf prim gavin_install.txtThe current Makefile was modified to try and fit into the current IOCCC build environment.
Please also see known features in the index.html for things that are not bugs but documented (mis)features.
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2004/hibachi
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STATUS: INABIAF - please DO NOT fix
Source code: 2004/hibachi/hibachi.c
Information: 2004/hibachi//index.html
The author stated that:
The links (text) web browser does not support RFC 2616 section 7.2.1 paragraph 3 sentence 2, and so fails to display responses from
hibachi.
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2004/jdalbec
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STATUS: INABIAF - please DO NOT fix
Source code: 2004/jdalbec/jdalbec.c
Information: 2004/jdalbec/index.html
The author stated that:
Arguments matching
/[^2]22$/cause the program to segfault after rapidly exhausting the available stack space. I could probably fix this by adding some special cases to the code, but [Blaine the Mono] it’s quite a bit more exciting this way, don’t you think?[/Blaine] Since the trailing22will be its own atom anyway, you can just insert a space in front of it if you run into this feature (e.g.1 22instead of122).Arguments matching
/(?:.){10,}/will produce visually incorrect results (e.g., generation 1 starting from 1111111111 will print as: 1), but there’s nothing interesting about these arguments that can’t be modeled using shorter runs of the same symbol.Arguments matching
/(?:.){257,}/may produce mathematically incorrect results (e.g., generation 1 starting from a string of 2571s will be calculated as11); the remark from the previous paragraph applies here also.
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2004/sds
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STATUS: INABIAF - please DO NOT fix
Source code: 2004/sds/sds.c
Information: 2004/sds/index.html
The generated code will very likely segfault or do something not intended if not given the right args. See the index.html file for the correct syntax.
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2005
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2005/anon
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STATUS: INABIAF - please DO NOT fix
Source code: 2005/anon/anon.c
Information: 2005/anon/index.html
This program sometimes will create unsolvable puzzles :-) just to hook you. As a protection against this - and to prevent you from spending too much time on such puzzles (or too big puzzles if you insist on doing this) - it deliberately destroys its runtime stack. See the index.html for more details on this.
If you specify more than three args the program might also crash or do something
strange. This might also happen if you specify excessively large board
dimensions. Try 100 100 100 for instance and see what happens!
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2005/giljade
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STATUS: INABIAF - please DO NOT fix
Source code: 2005/giljade/giljade.c
Information: 2005/giljade/index.html
This entry will very likely segfault or do something strange if the source code does not exist.
This entry will, according to the author, likely segfault if sizeof(int) != sizeof(FILE *).
This entry requires that sed and make are in your $PATH.
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2005/mikeash
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STATUS: INABIAF - please DO NOT fix
Source code: 2005/mikeash/mikeash.c
Information: 2005/mikeash/index.html
The author states:
The only built-in functions are
defvar,format,substitute,char-upcase,+,-,*, and/.Only one variable is available. This variable is called
q, although any symbol name starting with the letterqwill be mapped to this variable.Only the first letter of a function name is significant. For example,
format,f,farm, and various other words starting withfwill all map to theformatfunction.The
defvarfunction completely ignores its first parameter. It will always store the result of evaluating its second parameter inq. Unlike in Common Lisp, multiple invocations ofdefvaron the same variable will overwrite old values.Character constants are limited to
#\Newlineand single-character constants such as#\x.The
char-upcasefunction will give strange results if passed something other than a lowercase character.The
formatfunction takes exactly three parameters. The first parameter is ignored; output always goes tostdout. The second parameter must have exactly one~sformat specifier in it, and no other format specifiers are permitted.The arithmetic functions take exactly two parameters.
All tokens must be separated from a following
)by whitespace.A lot of other things. Notably, the language which this program interprets is nowhere near Turing-complete.
Basically, the LISP interpreter is good for some basic math operations, and for running itself.
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2005/mynx
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STATUS: INABIAF - please DO NOT fix
Source code: 2005/mynx/mynx.c
Information: 2005/mynx/index.html
Probably this is obvious, but this entry will not work with https. An
alt version exists that SCANS for https in case someone wants to set up a pipeline or
other workaround (perhaps with stunnel) or even add additional code to it to
make it work with https but the problem otherwise is a secure connection has to
first be set up in order to give http commands. This is not a bug but it’s worth
pointing out as it won’t work on as many websites as it used to including the
IOCCC website itself. The author noted that someone did
make a version that supports https but it is not known where this might be.
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2005/sykes
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STATUS: INABIAF - please DO NOT fix
Source code: 2005/sykes/sykes.c
Information: 2005/sykes/index.html
The author stated the below points of interest.
The machine emulated is an older 40 column one so 80 column programs will not show up correctly.
There is no emulation of PET graphics characters.
The parameter controls the speed of the 60Hz “jiffy clock”, and not the processor speed. This means many games may run too fast to be usable - it really depends on the speed of your machine.
Although the PET emulator can do LOAD
and SAVE, it cannot VERIFY or OPEN and CLOSE files.
The PET hardware emulation is not at all complete - features such as the hardware timers are completely missing. Some programs will not run correctly.
The 6502 emulation does not include the seldom used decimal mode, or any of the “undocumented” instructions.
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2006
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2006/birken
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STATUS: uses gets() - change to fgets() if possible
Source code: 2006/birken/birken.c
Information: 2006/birken/index.html
This entry uses gets(3) which is unsafe and provides annoying warnings, most
obnoxious in macOS as it shows it at runtime (redirecting stderr to
/dev/null will silence it). The following diff will almost work but it crashes
with at least computer.tofu input file:
12a13
#define gets(c) fgets((c),PI,stdin)&&(((c)[strlen((c))-1]='\0'),c!=NULL)Jump to: top
2006/borsanyi
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STATUS: INABIAF - please DO NOT fix
Source code: 2006/borsanyi/borsanyi.c
Information: 2006/borsanyi/index.html
The string specified must be <= 42 characters and may only consist of the
characters in the regex a-z_A-Z0-9@.-. Breaking these constraints will end up
with possibly corrupt GIF files.
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2006/hamre
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STATUS: INABIAF - please DO NOT fix
Source code: 2006/hamre/hamre.c
Information: 2006/hamre/index.html
This program will likely crash or do something funny without an arg.
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2006/monge
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STATUS: doesn’t work with some platforms - please help us fix it
Source code: 2006/monge/monge.c
Information: 2006/monge/index.html
This program requires x86 (with an x87 FPU) or x86_64 machine and it requires the SDL1 library.
This program also requires being able to read, write and execute memory. With the Apple silicon chips this is not allowed. Fixing this might be quite challenging but you are welcome to try and fix it.
If you do fix this it might be good to fix the alternate code as well or else provide it as an additional alt version. Fixing this is very likely to be very challenging and in some systems it will not be possible to fix but you are welcome to try and fix it if you wish to!
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STATUS: INABIAF - please DO NOT fix
Incorrect formulas will ungracefully crash the program.
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2006/stewart
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STATUS: INABIAF - please DO NOT fix
Source code: 2006/stewart/stewart.c
Information: 2006/stewart/index.html
This program will likely crash or do something funny if the file cannot be opened. The number of args is however checked.
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2006/sykes1
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STATUS: INABIAF - please DO NOT fix
Source code: 2006/sykes1/sykes1.c
Information: 2006/sykes1/index.html
The author stated:
If you pick a number higher than 19186, the program will return a solution but it will be a rotation of one of the first 19186. This is because the cross shaped piece fits 48 ways in the 4x4 cube, but only 2 of those ways are unique - you can rotate one of those to make any of the other 46. The algorithm used always places the cross piece first, so the first two placings of that piece result in the 19186 unique solutions.
If you pick a number higher than 460464 (24x19186) the program will return without outputting a solution. If you can wait that long.
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2006/toledo2
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STATUS: INABIAF - please DO NOT fix
Source code: 2006/toledo2/toledo2.c
Information: 2006/toledo2/index.html
This was fixed to
not crash in macOS (it appeared to work fine in fedora linux on an x86_64
architecture but it is not known if it crashed in macOS Ventura due to the fact
it is an arm64 CPU - the Apple silicon chip, but given that the author later
made some slight changes to make it not crash in x86_64 macOS that might be
the case).
Nevertheless there are two features that are not bugs.
By design this program is supposed to crash on termination. This actually no longer seems to happen but we don’t need this to be added even if it might be called a bug :-)
You must type in caps (except in strings) and this program is indeed case-sensitive.
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2007
There was no IOCCC in 2007.
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2008
There was no IOCCC in 2008.
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2009
There was no IOCCC in 2009.
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2010
There was no IOCCC in 2010.
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2011
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2011/borsanyi
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STATUS: INABIAF - please DO NOT fix
Source code: 2011/borsanyi/borsanyi.c
Information: 2011/borsanyi/index.html
For a great amount of data points the program will crash, depending on your available stack space.
Giving too few (distinct) points can also cause a crash or division by zero.
The program expects plain numbers separated by whitespace.
This program assumes ASCII.
If you give the program any arg it might flood the screen.
It requires both syscalls
fork(2)andwait(2).Giving any arg to the program is likely to flood your screen.
Rounding errors might cause an omission in the highest bin. There might be empty bins at the edges.
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2011/dlowe
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STATUS: missing or dead link or links - please provide it or them
Source code: 2011/dlowe/dlowe.c
Information: 2011/dlowe/index.html
The domain http://pootpoot.com no longer exists as it once did. The judges have
given a script that can be used to make a similar page (warning: not checked
for security in modern days!). Do you have a server with enough bandwidth and
would like to set it up? We’ll gladly thank you in the thanks
file file and link to the page as well! You’ll also have
IOCCC fame for reviving a pootifier! :-)
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STATUS: INABIAF - please DO NOT fix
The author states the following:
Bad input (e.g. nonexistent files, non-numeric number of iterations, etc.) tends to result in empty output.
Given exactly one corpus, the program will crash or produce garbage.
Leaks memory and file descriptors while processing files.
Will crash and die horribly if it runs out of memory.
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2011/fredriksson
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STATUS: INABIAF - please DO NOT fix
Source code: 2011/fredriksson/fredriksson.c
Information: 2011/fredriksson/index.html
The author stated that there are a number of features and limitations. As the list is rather long see other features and limitations and remarks instead.
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2011/konno
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STATUS: INABIAF - please DO NOT fix
Source code: 2011/konno/konno.c
Information: 2011/konno/index.html
This program will very likely crash or do something funny without an arg.
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2011/richards
STATUS: doesn’t work with some platforms - please help us fix it
Source code: 2011/richards/richards.c
Information: 2011/richards/index.html
This does not appear to work with macOS, resulting in a segfault (and sometimes a bus error).
We’re not sure if this is to do with the Apple silicon chip or not but it seems like it might (see Apple resources below) be but it could also be a wider problem with macOS. It appears that Apple does not allow certain combinations of memory protections with the arm64 processor.
Some of the workarounds have been tried but at this time it did not seem to work. Some earlier debugging sessions are below as well as a resource from the author as well as some resources on Apple’s website should anyone wish to take a crack at it. A starting point might be in richards.alt.c.
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Debugging
At first glance it appeared to be that it might be the function pointers or the
fact it is trying to execute code in memory (as noted above). The function
pointers were changed a bit but this has not helped solve the problem with
macOS. A few things that were noticed depending on asan sanitisers specified.
With address in linux:
richards.c:101:9: runtime error: null pointer passed as argument 2, which is declared to never be nullbut it actually works. This code is:
} else
p++;
W(c)} /* LINE 101 */
}Okay but what about argument 2? Well W is defined as:
#define W(c) e=memmove(e,x[(u)c], y[(u)c])+y[(u)c];so it would appear that
x[(u)c]is NULL. But why does it work then?
NOTE: u is int.
Under macOS (with the arm64 chip) we get:
UndefinedBehaviorSanitizer:DEADLYSIGNAL
==10834==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address 0xffffffffffffffff (pc 0x00019f446748 bp 0x00016f353100 sp 0x00016f352b90 T139066)
==10834==The signal is caused by a WRITE memory access.
#0 0x19f446748 in _platform_memmove+0xa8 (libsystem_platform.dylib:arm64e+0x3748) (BuildId: 756cd10d62a032839e57cbaa810c95ac32000000200000000100000000030d00)
#1 0x100c33c2c in main richards.c:202
#2 0x19f0bff24 (<unknown module>)
==10834==Register values:
x[0] = 0xffffffffffffffff x[1] = 0x0000000100ab18c1 x[2] = 0x00000000000000cf x[3] = 0x0000000000000000
x[4] = 0x0000000100ab18a1 x[5] = 0x0000000000000001 x[6] = 0x000000000000000a x[7] = 0x0000000000000000
x[8] = 0x00000001015972b8 x[9] = 0xffffffffffffffff x[10] = 0x0000000000000001 x[11] = 0x00000000000001f0
x[12] = 0x0000000000000001 x[13] = 0x00000000000003e0 x[14] = 0x0000000000000001 x[15] = 0x0000000000000084
x[16] = 0x000000019f4466a0 x[17] = 0x00000001ff3ad908 x[18] = 0x0000000000000000 x[19] = 0x0000000100c32a80
x[20] = 0x00000001017e0000 x[21] = 0x00000001017e1910 x[22] = 0x000000016f353530 x[23] = 0x000000019f13a366
x[24] = 0x000000016f3534b0 x[25] = 0x0000000000000001 x[26] = 0x0000000000000000 x[27] = 0x0000000000000000
x[28] = 0x0000000000000000 fp = 0x000000016f353100 lr = 0x0000000100aaf880 sp = 0x000000016f352b90
UndefinedBehaviorSanitizer can not provide additional info.
SUMMARY: UndefinedBehaviorSanitizer: SEGV (libsystem_platform.dylib:arm64e+0x3748) (BuildId: 756cd10d62a032839e57cbaa810c95ac32000000200000000100000000030d00) in _platform_memmove+0xa8
==10834==ABORTINGand naturally it does not work.
Adding the proper PROT_WRITE constant to the mmap() call does not seem to
help. Of course with the address this is not surprising so why is a different
address allocated in macOS? Or is it?
Now with address sanitiser both linux and macOS crash at:
=================================================================
==10983==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x00016f8d5e78 at pc 0x0001005dd910 bp 0x00016f8d5cd0 sp 0x00016f8d5cc8
READ of size 8 at 0x00016f8d5e78 thread T0
#0 0x1005dd90c in rd richards.c:132
#1 0x1005ddf8c in re richards.c:149
#2 0x1005110a0 in t richards.c:108
#3 0x1005df72c in main richards.c:189
#4 0x19f0bff24 (<unknown module>)
Address 0x00016f8d5e78 is located in stack of thread T0 at offset 56 in frame
#0 0x1005dd678 in rd richards.c:129
This frame has 2 object(s):
[32, 36) 'v.addr'
[48, 56) 'a' (line 130) <== Memory access at offset 56 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
(longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow richards.c:132 in rd
Shadow bytes around the buggy address:
0x00702df3ab70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00702df3ab80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00702df3ab90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00702df3aba0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00702df3abb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x00702df3abc0: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 04 f2 00[f3]
0x00702df3abd0: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
0x00702df3abe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00702df3abf0: 00 00 00 00 f1 f1 f1 f1 00 f3 f3 f3 00 00 00 00
0x00702df3ac00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00702df3ac10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
==10983==ABORTING
/bin/bash: line 1: 10983 Abort trap: 6 ./richardswhich corresponds to the code:
o rd(u v)
{
o *a = 0, **b = &a, **c = b + 32;
x[v] = w;
for (; b < c && (*b < (o *)w || *b > (o *) T || *b == &v); b++); /* LINE 132 */but this seems to not necessarily be relevant since without it it works in linux.
A warning of interest when compiling is:
richards.c:169:15: warning: incompatible pointer types initializing 'f *' (aka 'void (**)(volatile void *)') with an expression of type 'o ()' (aka 'void ()') [-Wincompatible-pointer-types]
f *lib1[] = { T, T, T, T, T } ;
...
richards.c:170:15: warning: incompatible pointer types initializing 'f *' (aka 'void (**)(volatile void *)') with an expression of type 'o ()' (aka 'void ()') [-Wincompatible-pointer-types]
f *lib2[] = { T, ld, lp, lx, l1 } ;
^
richards.c:170:18: warning: incompatible pointer types initializing 'f *' (aka 'void (**)(volatile void *)') with an expression of type 'void (volatile dt)' (aka 'void (struct (unnamed at richards.c:36:3) *volatile)') [-Wincompatible-pointer-types]
f *lib2[] = { T, ld, lp, lx, l1 } ;
^~
richards.c:170:22: warning: incompatible pointer types initializing 'f *' (aka 'void (**)(volatile void *)') with an expression of type 'void (volatile dt)' (aka 'void (struct (unnamed at richards.c:36:3) *volatile)') [-Wincompatible-pointer-types]
f *lib2[] = { T, ld, lp, lx, l1 } ;
^~
richards.c:170:26: warning: incompatible pointer types initializing 'f *' (aka 'void (**)(volatile void *)') with an expression of type 'void (volatile dt)' (aka 'void (struct (unnamed at richards.c:36:3) *volatile)') [-Wincompatible-pointer-types]
f *lib2[] = { T, ld, lp, lx, l1 } ;
^~
richards.c:170:30: warning: incompatible pointer types initializing 'f *' (aka 'void (**)(volatile void *)') with an expression of type 'void (volatile dt)' (aka 'void (struct (unnamed at richards.c:36:3) *volatile)') [-Wincompatible-pointer-types]
f *lib2[] = { T, ld, lp, lx, l1 } ;
^~This can be fixed easily enough however but it doesn’t appear to matter in this case.
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Testing fixes
It might be helpful to use the try.alt.sh script to test that it does not crash and functions properly.
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Resources
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More from the author
The author has more about the entry at https://github.com/GregorR/ioccc2011.
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Apple resources
Porting Just-In-Time Compilers to Apple Silicon
Allow Execution of JIT-compiled Code Entitlement
Looking at
https://github.com/apple/darwin-xnu/blob/5394bb038891708cd4ba748da79b90a33b19f82e/bsd/kern/kern_mman.c
A curious thing is in the mprotect() function: #if CONFIG_DYNAMIC_CODE_SIGNING and the protection variable has the
VM_PROT_TRUSTED set it might allow overriding the problem but this is
unconfirmed and it’s not known when CONFIG_DYNAMIC_CODE_SIGNING would be
defined.
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2011/vik
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STATUS: INABIAF - please DO NOT fix
Source code: 2011/vik/vik.c
Information: 2011/vik/index.html
The author stated that the program will crash if no argument is passed to the program though we note that your computer might also halt and catch fire :-)
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2012
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2012/blakely
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STATUS: INABIAF - please DO NOT fix
Source code: 2012/blakely/blakely.c
Information: 2012/blakely/index.html
The author stated:
If there is a division by zero, square-root of a negative number, or similar operation, then the results are undefined.
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2012/deckmyn
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STATUS: INABIAF - please DO NOT fix
Source code: 2012/deckmyn/deckmyn.c
Information: 2012/deckmyn/index.html
The author stated:
The memory locations of
argvare used for various purposes. Therefore, the program name (defaultdeckmyn) must be at least 4 characters long, including possibly the path. This, along with the ending'\0', gives a minimum 5 bytes of useful memory space. Otherwise, the program may attempt to write outside the string.The code is quite sensitive. Errors in the input can lead to strange results. The code does not read beyond the end of the music input, but that is about the only error checking available. Any input that is not according to the rules in the deckmyn.html, may cause errors.
The program has no special hardware limitations or requirements, other than 8bit
char(signedorunsigned) and two’s complement negatives.The limitations of using
charas counters for e.g. the number of music staves are minor. 127 staves to a page is rather a lot.The file layout must be exactly the same as deckmyn.c though, only the locations of space (
" ") may differ.Every element in the music is given by a string of exactly 3 characters. Any violation of this will result in the rest of the music being interpreted in some randomly wrong way. Notice that in a file, the newline is also a character! Therefore, when preparing music in a file, care should be taken that the last musical element of a line is only 2 characters!
The manual referred to is here.
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2012/dlowe
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STATUS: INABIAF - please DO NOT fix
Source code: 2012/dlowe/dlowe.c
Information: 2012/dlowe/index.html
The author stated:
- Flicker, especially at high speeds, and in spite of “double-buffering” (X11 doesn’t make it possible to lock drawing to the display refresh rate.)
- Cannot be run outside of the directory containing the data files (
splash.d,dead.dandsprites.d). - Cannot build or run without X11 (or an X11 compatibility layer).
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2012/tromp
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STATUS: INABIAF - please DO NOT fix
Source code: 2012/tromp/tromp.c
Information: 2012/tromp/index.html
The author stated:
If the input doesn’t start with a valid program, that is, if the interpreter reaches end-of-file during program parsing, it will crash in some way. E.g. the following might dump core:
echo -n "U" | ./trompFurthermore, the interpreter requires the initial encoded lambda term to be closed, that is, variable n can only appear within at least ‘n’ enclosing lambdas. For instance, here the term
'\ 5'is not closed, causing the interpreter to crash when looking into a null-pointer environment:
echo ">Hello, world" | ./trompwill likely dump core.
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2012/vik
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STATUS: INABIAF - please DO NOT fix
Source code: 2012/vik/vik.c
Information: 2012/vik/index.html
The author stated that the program will crash if no argument is passed to the program or if invalid arguments (e.g. file does not exist) or images of mismatching sizes or unsupported pixel formats though we note that your computer might also halt and catch fire :-)
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2013
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2013/cable2
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STATUS: INABIAF - please DO NOT fix
Source code: 2013/cable2/cable2.c
Information: 2013/cable2/index.html
The author stated:
- The width of input images must be a multiple of 4.
- Input images can be 8-bit greyscale, 24-bit color or 32-bit color only. 8-bit color and 16-bit color are not supported. If you use the “color” command-line feature, do not use a greyscale input file!
- Normal Windows BMP files are stored “upside-down”, i.e. the bottom line in the image is written first. Some (old) graphics programs actually write BMP files “top-to-bottom” and the program does not support such files.
- Using anti-aliased brush strokes to draw your letters is fine; however, antialiasing interferes with color detection in “color” mode.
- Only runs on little endian machines (since the BMP format is little endian, and endianness conversion would make the source too large for IOCCC rule 2).
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2013/dlowe
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STATUS: INABIAF - please DO NOT fix
Source code: 2013/dlowe/dlowe.c
Information: 2013/dlowe/index.html
This program will possibly crash or draw something strange with 0 args. Then again it might not. :-) This is easy to fix but would add bytes and since the author noted it is a feature and not a bug. You of course can try and fix it yourself but please do NOT open a pull request for this: just do it as an exercise to see if you understand the code.
You can try and answer the questions, too: when will it crash? When will it draw something funny (or will it? :-) ) and when will it just do nothing?
The author also stated:
- Produces bogus graphs when given > about 5000 arguments.
- Only works if your terminal is UTF-8 and your font supports the 8 glyphs used.
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2013/endoh1
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STATUS: INABIAF - please DO NOT fix
Source code: 2013/endoh1/endoh1.c
Information: 2013/endoh1/index.html
This program supports only “Combinator-calculus style notation” of Lazy K. “Unlambda style” and “Iota and Jot” style are not supported.
Also, it requires a space between identifiers. In short, use
(S K)instead of(SK), “`sk”,**i*i*i*ii*i*i*ii, or11111100011100.Huge memory may be required to compile the program (about 300 MB on my machine).
In addition, there are some limitations (and workarounds) mentioned in the obfuscation section.
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2013/endoh3
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STATUS: INABIAF - please DO NOT fix
Source code: 2013/endoh3/endoh3.c
Information: 2013/endoh3/index.html
From the author:
You can NOT write a note length immediately followed by a note
E, such asC2E2.Can you figure out why?
A workaround is inserting a whitespace:
C2 E2.
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2013/endoh4
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STATUS: INABIAF - please DO NOT fix
Source code: 2013/endoh4/endoh4.c
Information: 2013/endoh4/index.html
Invalid input files will very likely crash the program.
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2013/hou
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STATUS: INABIAF - please DO NOT fix
Source code: 2013/hou/hou.c
Information: 2013/hou/index.html
This program will not terminate on its own; you must kill hou (but not Qiming
Hou :-) ) yourself. This should not be fixed.
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2013/mills
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STATUS: INABIAF - please DO NOT fix
Source code: 2013/mills/mills.c
Information: 2013/mills/index.html
The author reminds us that if you kill the program you will have to wait a short bit of time before you can start it again if you want it to be able to bind to the socket (which obviously you do). The source is out the scope of this document but the author does mention the well known (at least to those of us who have experience with socket programming :-) ) fix. However as the author pointed it out as a known limitation it is not a bug but a feature.
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2014
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2014/maffiodo1
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STATUS: INABIAF - please DO NOT fix
Source code: 2014/maffiodo1/prog.c
Information: 2014/maffiodo1/index.html
The author noted that in macOS the colours might be wrong and gives a solution, though it is unclear if this is still true or if there was any problem at all.
The author noted that the character cannot go through walls and the impression is that this is how it was believed but someone did ironically point out that there are known glitches where in some places you actually could go through walls. This might even have applied to the arcade version, Mario Bros, though that can no longer be confirmed by said person. The point here is that in this game you cannot go through walls but it’s not a bug.
On the other hand, the author also stated:
When the
Super characterbecomes bigger (ZOOMflag), the character can collide with blocks and get stuck inside them. This is a KNOWN BUG. When your player become bigger, stay away from blocks!
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2014/maffiodo2
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STATUS: INABIAF - please DO NOT fix
Source code: 2014/maffiodo2/prog.c
Information: 2014/maffiodo2/index.html
This program will very likely crash if no arg is given.
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2014/vik
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STATUS: known bug - please help us fix
Source code: 2014/vik/prog.c
Information: 2014/vik/index.html
Cody Boone Ferguson discovered a bug to do
with translating sound to text that shows itself in some cases (it works in
others) when working on his winning 2020 Enigma machine
(‘Most enigmatic’) entry. See his index.html for
details (search for vik in the file). This one might be more of a limitation
but this is not known.
He provides a tip in testing the problem: it might help to use his Enigma machine to find problems as it will allow you to verify what is correct and what is not. Again see his index.html for details. However it is also possible to not rely on the entry as the below shows. One should be able to do:
echo 'No. I want chocolate!' | ./prog > chocolate.raw
./prog e < chocolate.rawand get:
No. I want some chocolate!but instead we get:
IT FHOCOLITE!which is very wrong. If however one does:
echo IOCCC | ./prog > ioccc.raw
./prog e < ioccc.rawthey will properly get:
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2015
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2015/duble
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STATUS: INABIAF - please DO NOT fix
Source code: 2015/duble/prog.c
Information: 2015/duble/index.html
This program is known to, in some cases, segfault, and as the judges and the author noted this, it should not be fixed.
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2015/hou
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STATUS: INABIAF - please DO NOT fix
Source code: 2015/hou/prog.c
Information: 2015/hou/index.html
The author stated:
Hard requirements:
The platform must implement the
doubletype as IEEE754-compliant 64-bit floating point numbers. The 80-bit intermediate format used by x87 is considered as an violation of this. The code should print an error message on such platforms.The program must start with the CPU / FPU in round-to-nearest mode.
Soft requirements:
The compiler must respect
volatile. The code is formatted to warn about that, though.The printed result is only correct on little-endian machines. The program takes care to warn about this issue after printing an incorrect big-endian result. Error messages become garbled, though.
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2015/howe
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STATUS: known bug - please help us fix
The test scripts do not seem to work properly with bash but this would be ideal as not all systems have a compatible shell (they assume a POSIX compliant shell). One, with bash, might see:
./prog-test.sh
<<< A='1' B='1'
prog: : No such file or directory
>>> got=0 expect=0 -OK-
<<< A='1' B='A'
prog: : No such file or directory
>>> got=0 expect=2 FAILIt would appear that the variable passed to the command in the function,
distance, is empty.
The same problem exists in the
prog.alt-test.sh, particularly
because it is the same thing as the other, just updated to use prog.alt.
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2015/mills2
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STATUS: INABIAF - please DO NOT fix
Source code: 2015/mills2/prog.c
Information: 2015/mills2/index.html
The program doesn’t look at the header of files so if it’s passed something hat is not compressed data it’s likely to crash.
The program depends on little endian systems.
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2015/schweikhardt
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STATUS: INABIAF - please DO NOT fix
Source code: 2015/schweikhardt/prog.c
Information: 2015/schweikhardt/index.html
The program assumes that EOF is -1. This can be fixed but at this time it is
uncertain if it should be.
The author also stated:
While the program works best when bytes/characters are octets and the number of bits in a type is
sizeof(typ) << 3, it will work correctly on 24-bit or 36-bit systems with 9 bits/byte, or systems wheresizeof(typ)is 1 even forintand so on. On such systems, it will only use8 * sizeof(typ)bits per place. It does not work whenCHAR_BIT <= 7.
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2016
There was no IOCCC in 2016.
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2017
There was no IOCCC in 2017.
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2018
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2018/algmyr
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STATUS: INABIAF - please DO NOT fix
Source code: 2018/algmyr/prog.c
Information: 2018/algmyr/index.html
The author wrote:
- There is no error checking done when opening files, so expect segfaults if you provide the wrong path to a file.
- This program is bound to misbehave if
intis less than 32 bits. - Flags will only be interpreted correctly if they are the first argument. Reading
a file named
-dor-his fully possible if it is not the first file provided, even though I am not sure why you would want to do that. - Providing invalid/unexpected arguments to the decode flag will result in odd behavior. Some erroneous arguments cause segfaults (negative number of channels, channel id outside valid range). One argument in particular causes an infinite loop printing whitespace.
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2018/hou
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STATUS: INABIAF - please DO NOT fix
Source code: 2018/hou/prog.c
Information: 2018/hou/index.html
When you run it on a JSON file you will see something like:
$ ./prog < ioccc.json > ioccc.html
Assertion failed: (rulez), function C, file prog.c, line 124.
Abort trap: 6(from say running ./try.sh) but this is expected and the file ioccc.html will
be generated properly.
Some JSON files might cause the program to continue to run and seemingly
infinitely increase the size of the output file. This can happen if you try
fixing the syntax error in the generated ioccc.json file.
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2018/mills
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STATUS: known bug - please help us fix
Source code: 2018/mills/prog.c
Information: 2018/mills/index.html
After exiting the program (with ctrl-e) if you try running it again you will likely see:
>bootT5pw
]h_ 8D3[]where [] is the cursor. When this happens if you hit enter (this is necessary
or else it’ll happen again) and then exit again (ctrl-e) and run prog again
it’ll be okay.
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STATUS: INABIAF - please DO NOT fix
The author stated that if you make a typo it can happen that the boot loader can crash and halt. If this is the case type ctrl-e to quit the emulator and try again.
The author also stated that it is possible to corrupt the virtual disk. If you
do this you should type make clobber all and try again.
A funny problem where it showed ERROR after each command was noticed. The
solution was to hit ctrl-e and start again. It is not known if this is what was
referred to by the author but there was likely no typo involved.
Another issue noticed is that if you are using the saved mode you must type
sync prior to exiting the program or else the next time you run it the file
will not exist (or in the case of compiled code it won’t be executable).
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2018/vokes
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STATUS: INABIAF - please DO NOT fix
Source code: 2018/vokes/prog.c
Information: 2018/vokes/index.html
The author wrote the following:
Despite appearances, it does not handle numbers in hex, or provide a
curses(3)-based interface.The expected input format is zero or more lines of space-separated integers. If other characters appear in the input, it will either reject the input entirely and exit with a non-zero status, or skip number(s) adjacent to the non-digit characters, depending on where the characters appear. Tabs and multiple consecutive spaces are handled correctly, however.
Individual lines of input longer than
0x3543 - 1bytes will be split and processed as if they were multiple lines of input, which can produce incorrect results. This magic number’s significance is described earlier.The algorithm expects its input to represent a fully connected graph. While the output is otherwise topologically sorted, if there are nodes completely unconnected to the rest of the graph (with or without self-cycles), they will be output as soon as they are processed – this means that, when there are disconnected nodes, reordering the input lines can produce different output. Addressing this by adding another pass is would put the program over the size limit.
While the node IDs don’t need to be consecutive or start at 0, the implementation doesn’t have special handling for sparse graphs. If you give it a graph with nodes numbered 0 and 2147483647, it will attempt to allocate sufficient memory (potentially around 32 GB) for the entire range of graph nodes, even if those are the only ones. If memory allocation returns NULL, it will gracefully exit, otherwise it will succeed, eventually, perhaps after a great deal of swapping.
Node IDs >= 2147483648 will cause the program to print an error message and exit with a non-zero status. This shrinks the code that detects overflowing the array size by a bit.
A very large group of nodes in a cycle can cause a stack overflow. This typically takes over 100,000 nodes, and depends on the order the nodes are visited. Addressing this would put the program over the size limit.
The implementation depends on the characters
'0','1', …'9'having the values48through57, rather than usingisdigit(3). As noted above, this program has nothing to do with a hand.
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2019
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2019/adamovsky
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/adamovsky/prog.c
Information: 2019/adamovsky/index.html
Certain input can crash this program. The file crash.unl is an example file.
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2019/burton
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/burton/prog.c
Information: 2019/burton/index.html
The author pointed out that some implementations of wc(1) show different
values but his implementation matches that of macOS and FreeBSD.
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2019/ciura
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/ciura/prog.c
Information: 2019/ciura/index.html
The scripts were fixed so that they can work but it might end up that the scripts don’t show any output anyway as they use the full alphabet. To test that it works one can have a script like:
LC_ALL=C aäbcdefghijklmnoöpqrsßtuüvwxyz | LC_ALL=C grep .. | LC_ALL=de_DE.UTF-8 ./prog aäbcdefghijklmnoöpqrsßtuüvwxyzIf you run this you should see:
aäbcdefghijklmnoöpqrsßtuüvwxyzwhich shows it works. However as the de.sh script refers to all letters it can’t find a perfect pangram. BTW, as far as the question of whether the umlaut letters or the Eszett are considered letters in the German alphabet, it is noted in the de.sh/de.alt.sh scripts:
# Are the umlauts ä, ö, ü and Eszett (ß) letters in the German alphabet? There
# is more than one opinion on the subject but a lot of words do have an umlaut
# (or Umlaut in German). In some (probably all) systems this script outputs
# nothing probably because it's very hard to form a perfect pangram in German,
# if it's not impossible. Nevertheless, we do include the other characters
# whether or not they are in your view considered part of the alphabet for the
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2019/dogon
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STATUS: uses gets() - change to fgets() if possible
Source code: 2019/dogon/prog.c
Information: 2019/dogon/index.html
The entry calls gets(3) and it would be better if the code called fgets() instead.
See the
FAQ on “gets and fgets”
for more information on the change to fgets(3).
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2019/duble
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/duble/prog.c
Information: 2019/duble/index.html
There are two things to be aware of with this entry.
If the file being used (to draw) is deleted it might lock any session still in use. These will have to be killed from another shell session or by closing the terminal tab. This will also happen if the file cannot be opened in the beginning.
This program will also very likely leave sockets lying about in the current working directory. For instance Cody Boone Ferguson showed us this:
$ ls -al |grep '^s'
srwxr-xr-x 1 cody staff 0 Apr 6 08:19 .BDHFHALG=
srwxr-xr-x 1 cody staff 0 Apr 6 08:15 .CGGHAMGC=
srwxr-xr-x 1 cody staff 0 Apr 6 08:16 .CMDGAELH=
srwxr-xr-x 1 cody staff 0 Apr 3 08:47 .CMLBCCDA=
[...]This is NOT a bug and you’ll have to delete the files manually. You shouldn’t have to worry about these being added to git: it seems to ignore sockets (it did at least in macOS).
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Tips on this situation. A simpler way to find sockets in the directory:
file .*|grep socket|cut -f1 -d:To delete them you can do:
find . -exec file '{}' \;|grep socket|cut -f 1 -d: | xargs rm -fthough one might want to check that the program is not currently running. :-)
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2019/endoh
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/endoh/prog.c
Information: 2019/endoh/index.html
As a backtrace quine this entry is SUPPOSED to segfault so this should not be touched either.
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2019/karns
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/karns/prog.c
Information: 2019/karns/index.html
The author stated the following:
- The program must be ran in a terminal that supports ANSI escape codes for moving the cursor and changing colors.
- Segfaults happen sometimes.
- I don’t know what memory management there is, if any.
- The program will not compile by an ANSI C compiler: it uses for loops, and it uses C++ style comments. It should compile cleanly using a C99 standard.
- Breadth first search is slow (and very slow on certain maps), but my A star version of this program is too big.
- Lots of extra whitespace may be needed if you want to feed in an arbitrary file.
- It fails to compile on GCC sometimes (according to a friend of mine, I’ve not encountered this myself).
- The program could be obfuscated much further.
- The program contains some unused code and data.
NOTE: the segfault problem might have been fixed when the optimiser was disabled (which was necessary as part of a bug fix).
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2019/lynn
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/lynn/prog.c
Information: 2019/lynn/index.html
The author wrote that there are a number of differences from what one might expect. Rather than duplicate the information we refer you to the author’s remarks in the sections Syntax and Caveats.
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2019/mills
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/mills/prog.c
Information: 2019/mills/index.html
The author wrote that if you decide to change networks or use a different input file you should delete all the checkpoint files because the format depends on both the network and the input – using the wrong checkpoint is likely to cause a crash.
The author also wrote:
IMPORTANT NOTE: Since OMLET uses the system stack for network storage, larger networks may cause OMLET to crash (typically with a message like Segmentation fault) unless the system stack size is first increased. The exact command for doing so depends on your shell and your system’s hard limits. On sh/ksh/bash shells, you can view the hard limit with ulimit -Hs and set it with ulimit -s 65532 (replacing 65532 with the actual hard limit). On csh/tcsh shells, you can view the hard limit with limit -h stacksize and set it with limit stacksize 65532 (replacing 65532 with the actual hard limit).
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2019/poikola
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/poikola/prog.c
Information: 2019/poikola/index.html
This program will not validate input so it might fail or get stuck if invoked erroneously.
Also, the maximum file size is 1GB.
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2019/yang
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STATUS: INABIAF - please DO NOT fix
Source code: 2019/yang/prog.c
Information: 2019/yang/index.html
The author noted that if the program runs out of memory it is likely to crash.
The author also stated that ‘if input contains CR-LF end of line sequences,
those CRs are silently dropped. In fact, most control codes are silently
ignored except line feeds (preserved) and tabs (expanded to 8 spaces).’
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2020
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2020/burton
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STATUS: INABIAF - please DO NOT fix
Source code: 2020/burton/prog.c
Information: 2020/burton/index.html
This entry is known to crash if no arg is specified. Although easy to fix it is documented and should not be fixed (of course you may fix it to see if you can but it shouldn’t be made into a pull request).
It will also show funny output with more than one arg. This should not be fixed either. But can you figure out why this happens?
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2020/carlini
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STATUS: INABIAF - please DO NOT fix
Source code: 2020/carlini/prog.c
Information: 2020/carlini/index.html
The author stated that bad things happen if the entered move is outside of the
range [1..9]. We observed a crash but we also observed a tie and other things
besides (say with the input -1, -, -10 and others).
If a player makes a move over their opponent’s place they will automatically lose.
If a player tries to play a move they already played they will forfeit their move.
If you have audible bells enabled the program will beep at every turn.
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2020/ferguson1
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STATUS: INABIAF - please DO NOT fix
Source code: 2020/ferguson1/prog.c
Information: 2020/ferguson1/index.html
There are some things that might appear to be bugs but are actually features or things that are misinterpreted as bugs. See the bugs.html and troubleshooting.html files for details.
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2020/giles
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STATUS: INABIAF - please DO NOT fix
Source code: 2020/giles/prog.c
Information: 2020/giles/index.html
The author noted that the program only supports WAV files that have exactly 16 bits per sample, but it allows any sample rate and any number of audio channels.
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2020/otterness
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STATUS: INABIAF - please DO NOT fix
Source code: 2020/otterness/prog.c
Information: 2020/otterness/index.html
The author listed the following limitations:
The program does not support MIDI files over 4 MB (specifically, it will not take input files larger than
2^22 - 1bytes). This is unlikely to be a big limitation in practice, since even lengthy MIDIs are rarely over a couple hundred KB.Not all MIDIs set (or correctly set) their timing information, which will lead to the tempo of the drum beat not matching the track. This will be especially true for “live performance” .mid files.
There may be some types of MIDI messages that the program is unable to correctly parse, but I have rarely seen this in practice. The largest cause of program failures, in my experience, has been Limitation 2.
See also the Program error codes written by the author which lists some other conditions which should be considered features, not bugs.
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2021
There was no IOCCC in 2021.
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2022
There was no IOCCC in 2022.
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2023
There was no IOCCC in 2023.
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2024
We plan to run IOCCC28 this year but the time has not been announced just yet.
Final words
We hope this document was of use to you in determining which entries are known to have a problem, what entries are known to have features that are not bugs and so on. We also thank you for going through this document and, if you propose any fixes] via a GitHub pull request or otherwise, we thank you as well for the help! We will happily add you to the thanks file as well.
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