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 in bugs.html.

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

Primary files

• prog.c - entry source code
• Makefile - entry Makefile
• prog.orig.c - original source code
• try.sh - script to try entry
• ascii.c - shows character value of ASCII values

Secondary files

• 2019_endoh.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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