gdb question
in [Unix Programming]
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From: cerr on 18 Mar 2010 14:00 Hi There, I have a question. I'm running into a segfault but on bt i do not get source code but only useless addresses. I've done the following: - loaded my binary with symbol-file - compiled binary with following flags: -g3 -O0 -g - executed gdb from the source directory - set dir to "./" Why am I still not seeing the source code? :o Thanks for a little help here! -- Ron
From: Ben Bacarisse on 18 Mar 2010 14:10 cerr <ron.eggler(a)gmail.com> writes: > I have a question. I'm running into a segfault but on bt i do not get > source code but only useless addresses. > I've done the following: > - loaded my binary with symbol-file > - compiled binary with following flags: -g3 -O0 -g The mixture of -g3 and -g seems odd. At best I'd imagine that the latter -g is the one that governs the compile and -g is -g2 by default. > - executed gdb from the source directory > - set dir to "./" > > Why am I still not seeing the source code? :o Is the fault in a part of the code for which there are no symbols? E.g. in a library that you did not compile with -g. > Thanks for a little help here! Posting some/all of the output might give a vital clue. -- Ben.
From: cerr on 18 Mar 2010 14:17 On Mar 18, 11:10 am, Ben Bacarisse <ben.use...(a)bsb.me.uk> wrote: > cerr <ron.egg...(a)gmail.com> writes: > > I have a question. I'm running into a segfault but on bt i do not get > > source code but only useless addresses. > > I've done the following: > > - loaded my binary with symbol-file > > - compiled binary with following flags: -g3 -O0 -g > > The mixture of -g3 and -g seems odd. At best I'd imagine that the > latter -g is the one that governs the compile and -g is -g2 by > default. > > > - executed gdb from the source directory > > - set dir to "./" > > > Why am I still not seeing the source code? :o > > Is the fault in a part of the code for which there are no symbols? > E.g. in a library that you did not compile with -g. I would not think so... > > > Thanks for a little help here! > > Posting some/all of the output might give a vital clue. The output looks like this: Program received signal SIGSEGV, Segmentation fault. 0xb7f009b3 in ?? () (gdb) bt #0 0xb7f009b3 in ?? () #1 0xbf9c43e4 in ?? () #2 0xbf9c4384 in ?? () #3 0xbf9c4328 in ?? () #4 0xb7f1bff4 in ?? () #5 0x4ba2695f in ?? () #6 0xb7f1bff4 in ?? () #7 0xbf9c43e4 in ?? () #8 0x00000000 in ?? () (gdb) Thanks! -- Ron
From: Andrew Poelstra on 18 Mar 2010 14:31 On 2010-03-18, cerr <ron.eggler(a)gmail.com> wrote: > On Mar 18, 11:10�am, Ben Bacarisse <ben.use...(a)bsb.me.uk> wrote: >> cerr <ron.egg...(a)gmail.com> writes: >> > I have a question. I'm running into a segfault but on bt i do not get >> > source code but only useless addresses. >> > I've done the following: >> > - loaded my binary with symbol-file >> > - compiled binary with following flags: -g3 -O0 -g >> >> The mixture of -g3 and -g seems odd. �At best I'd imagine that the >> latter -g is the one that governs the compile and -g is -g2 by >> default. >> >> > - executed gdb from the source directory >> > - set dir to "./" >> >> > Why am I still not seeing the source code? :o >> >> Is the fault in a part of the code for which there are no symbols? >> E.g. in a library that you did not compile with -g. > > I would not think so... >> >> > Thanks for a little help here! >> >> Posting some/all of the output might give a vital clue. > > The output looks like this: > Program received signal SIGSEGV, Segmentation fault. > 0xb7f009b3 in ?? () > (gdb) bt > #0 0xb7f009b3 in ?? () > #1 0xbf9c43e4 in ?? () > #2 0xbf9c4384 in ?? () > #3 0xbf9c4328 in ?? () > #4 0xb7f1bff4 in ?? () > #5 0x4ba2695f in ?? () > #6 0xb7f1bff4 in ?? () > #7 0xbf9c43e4 in ?? () > #8 0x00000000 in ?? () > (gdb) If you've got debug symbols in there, try: (gdb) break 1 (gdb) run (gdb) x 0xb7f009b3 And examine each of those hex addresses while the program is running. (This assumes you don't crash before line 1.) -- Andrew Poelstra http://www.wpsoftware.net/andrew
From: Ben Bacarisse on 18 Mar 2010 14:44
cerr <ron.eggler(a)gmail.com> writes: > On Mar 18, 11:10 am, Ben Bacarisse <ben.use...(a)bsb.me.uk> wrote: >> cerr <ron.egg...(a)gmail.com> writes: >> > I have a question. I'm running into a segfault but on bt i do not get >> > source code but only useless addresses. >> > I've done the following: >> > - loaded my binary with symbol-file On re-reading this is curious. There is less possibility for a mistake if gdb find the symbols from the file it is running. >> > - compiled binary with following flags: -g3 -O0 -g >> >> The mixture of -g3 and -g seems odd. At best I'd imagine that the >> latter -g is the one that governs the compile and -g is -g2 by >> default. >> >> > - executed gdb from the source directory >> > - set dir to "./" >> >> > Why am I still not seeing the source code? :o >> >> Is the fault in a part of the code for which there are no symbols? >> E.g. in a library that you did not compile with -g. > > I would not think so... >> >> > Thanks for a little help here! >> >> Posting some/all of the output might give a vital clue. > > The output looks like this: > Program received signal SIGSEGV, Segmentation fault. > 0xb7f009b3 in ?? () > (gdb) bt > #0 0xb7f009b3 in ?? () > #1 0xbf9c43e4 in ?? () > #2 0xbf9c4384 in ?? () > #3 0xbf9c4328 in ?? () > #4 0xb7f1bff4 in ?? () > #5 0x4ba2695f in ?? () > #6 0xb7f1bff4 in ?? () > #7 0xbf9c43e4 in ?? () > #8 0x00000000 in ?? () > (gdb) > Thanks! It's possible that gdb can't give you a stack trace because the stack has been messed up. Step through the program skipping over everything but the top-level functions to find where the fault it. Keep going deeper as you get closer to fault. Have you tried other tools like valgrind? -- Ben. |