DragonFly users List (threaded) for 2008-02
DragonFly BSD
DragonFly users List (threaded) for 2008-02
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Re: how to attach to gdb forked child?

From: "Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>
Date: Sun, 17 Feb 2008 09:55:19 +0100

Jeremy C. Reed wrote:
I am trying to figure out where an abort core dump in imake is coming from, so I do:

For a core dump, you should be able to get a nice backtrace from the dump.

(gdb) n
458 cppit(cleanedImakefile, Template, ImakefileC, tmpfd, tmpMakefile);
(gdb) n

So now I have a new process id.

Are are you sure you have the new process id? Are you also sure that the child process is still running? It might finish before you can attach to it.

Looking at source I see for its get_stackprotector:

   1059   }
   1060   if (pclose(fp))
   1061     abort();
   1062 }

imake assumes the cc -v output is several lines.

Why would pclose fail in this case?

So I see where the problem is probably at -- but can someone teach me how to find it with gdb itself?

That's not so easy. We'd need to have gdb's follow-fork-mode, which lets you choose to debug the child instead. As we don't have it, you might use this "trick": Add a sleep(10) to the child directly after the fork. Then you have some time to attach to the child. I don't like this, but it seems to be the only possibility so far.


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