On Friday 02 Jan 2004 11:32 pm, John Richard Smith wrote: > so when you get through the pre-amble it doesn't say much really,but, > Core was generated by `mencoder dvd://1 -ovc lavc -lavcopts > vcodec=mpeg4:vhq:vbitrate=1024 -oac mp3lam'. > Program terminated with signal 11, Segmentation fault. > #0 0x081b5fb8 in ?? () > (gdb) > > So you see I'm trying to run down a problem with mencoder, but this core > dump doesn't really say much, unless #0 0x081b5fb8 in ?? () is saying > something cryptic I cannot possibly understand. I don't suppose someone > knows if it is ?
If you use: gdb -core=core.7674 /usr/bin/mencoder (or whereever mencoder lives on your system) you may get a little more information. It will convert the hexadecimal address into an address in the source code. You will be able to use this information better if you have the source code handy. You can use the stack backtrace commands to find which functions are active. One of which may have the bug. You can dissassemble code around 0x081b5fb8 to find which address is triggering the segmentation fault. To find the bug you will need an understanding of C (or whatever else mencoder is written in,) and assembler. Otherwise the best you can do is grab a copy of the stack backtrace and mail it to the developers. The hexadecimal version isn't going to be any use to them; they need the functions names and line numbers. So use the command above, and then issue the "backtrace" command to gdb. For example: If the executable is built without debugging information you will get something like: (gdb) backtrace #0 0x08048368 in fail () #1 0x0804839d in main () #2 0x40038c57 in __libc_start_main () from /lib/i686/libc.so.6 And if it is built with debugging information you will get something like: (gdb) backtrace #0 0x08048368 in fail (ptr=0x0) at segfault.c:3 #1 0x0804839d in main () at segfault.c:8 #2 0x40038c57 in __libc_start_main () from /lib/i686/libc.so.6 Without the executable you will end up with something like this: (gdb) backtrace #0 0x08048368 in ?? () #1 0xbffff3c8 in ?? () #2 0x0804839d in ?? () #3 0x40038c57 in ?? () -- Richard Urwin
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