Gdb on multiple instance

Question

I have multiple instances of a particular process running on my system . At some point during the process execution, some of the internal data structures gets overwritten with invalid data. This happens on random instances at random intervals. Is there a way to debug this other than by setting memory access breakpoints?. Also, is it possible set memory access breakpoint on all these process simultaneously without starting a separate instance of gdb for each process?. The process runs on x86_64 linux system with 2.6 kernel.

score 0 · Answer 1 · answered Mar 15 '15 at 08:52

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If you haven't already done so, would recommend using valgrind (http://valgrind.org). It can detect many types of memory bugs including memory over/under runs, memory leaks, double frees, etc.

answered Mar 15 '15 at 08:52

kaylum

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score 0 · Answer 2 · answered Mar 15 '15 at 11:50

Also, is it possible set memory access break-point on all these process simultaneously without starting a separate instance of gdb for each process?

I don't think so that using gdb you can set breakpoints for all the processes in one go. According to me, you have separately attach each process and set the breakpoints.

score 0 · Answer 3 · answered May 14 '15 at 16:27

For memory errors, valgrind is much more useful than GDB. Assuming the instances you are talking about are forked or spawned from a single parent, you don't need separate instances of valgrind. Just use valgrind --trace-children=yes

See http://man7.org/linux/man-pages/man1/valgrind.1.html

As to your question on GDB, an instance can debug one process at a time only.

score 0 · Answer 4 · answered May 14 '15 at 16:41

You can only debug one process per gdb session. If your program forks, gdb follows the parent process if no other options to set follow-fork-mode was given.

see: http://www.delorie.com/gnu/docs/gdb/gdb_26.html

If you have memory problems it is even possible to run valgrind in combination with gdb or use some other memory debugging library like efence. Efence replaces some library calls e.g. malloc/free with own functions. After that efence and also valgrind use the mmu to catch invalid memory access. This is typically done by adding some space before and after each allocated memory block. If this spare memory is accessed by your application the library ( efence ) or valgrind stops execution. In connection with gdb you will be pointed to the source line which access the forbidden memory area.

Having multiple processes needs multiple instances of gdb which is in practive no real problem.

Gdb on multiple instance

4 Answers4