Author:

• Name: Yusuke Endoh
  Location: JP - Japan
  
  

To build:

make

NOTE: the use of the C compiler optimiser was disabled and -g was enabled for this entry because it is SUPPOSED to crash and it needs debugging symbols.

Bugs and (Mis)features:

The current status of this entry is:

STATUS: INABIAF - please **DO NOT** fix

For more detailed information see 2019 endoh bugs.

To use:

./prog

Try:

If you have gdb(1) installed:

./try.sh

Note that in macOS installing gdb(1) takes multiple steps - it’s not just a matter of installing gdb(1) and that’s that. The try.sh script has only been tested with linux.

You might also wish to try:

gdb ./prog || lldb ./prog

and then type in r (to run program) and then bt (for backtrace).

Judges’ remarks:

The purpose of this program is to crash. You’ll want to have memorized man 7 ascii when debugging it to reveal its purpose.

Author’s remarks:

backtrace quine:

Compile prog.c with no optimization.

cc -g -O0 -o prog prog.c

Then, run it. You will see a segmentation fault.

$ ./prog
Segmentation fault (core dumped)

Let’s debug. As usual, run it under gdb.

$ gdb ./prog
(gdb) run
Starting program: /home/.../prog

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()

Okay, check the backtrace.

(gdb) backtrace
#0  0x0000000000000000 in ?? ()
#1  0x0000555555555201 in x23 () at prog.c:35
#2  0x000055555555571a in x64 () at prog.c:100
#3  0x0000555555555747 in x65 () at prog.c:101
#4  0x0000555555555774 in x66 () at prog.c:102
#5  0x00005555555557ce in x69 () at prog.c:105
#6  0x0000555555555828 in x6e () at prog.c:110
#7  0x0000555555555747 in x65 () at prog.c:101
    ...

See the line numbers and lookup the ASCII table.

 35 = '#'
100 = 'd'
101 = 'e'
102 = 'f'
105 = 'i'
110 = 'n'
101 = 'e'
...

One more thing:

The original program can be used as a GDB command file.

gdb -q -x prog.c ./prog | cat
Reading symbols from ./prog...done.

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
#0  0x0000000000000000 in ?? ()
#1  0x0000555555555201 in x23 () at prog.c:35
#2  0x000055555555571a in x64 () at prog.c:100
#3  0x0000555555555747 in x65 () at prog.c:101
#4  0x0000555555555774 in x66 () at prog.c:102
#5  0x00005555555557ce in x69 () at prog.c:105
#6  0x0000555555555828 in x6e () at prog.c:110
#7  0x0000555555555747 in x65 () at prog.c:101
...

By using this, you can confirm that it is actually a quine.

gdb -q -x prog.c ./prog | sed -n -r 's/#.*:([0-9]+)/\1/p' | awk '{printf "%c",$1}' > prog2.c
diff prog.c prog2.c

Inventory for 2019/endoh

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Primary files

• prog.c - entry source
• Makefile - entry Makefile
• prog.orig.c - original source
• try.sh - how to run
• ascii.c - shows character value of ASCII
• 2019_endoh.tar.bz2 - download entry source

Secondary files

• index.html - entry home page
• README.md - markdown source for index.html
• .entry.json - description of entry in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top directory