Question

So when glibc crashes, it has a *glibc detected * crash message. It then prints a bunch of backtraces, like

*** glibc detected *** ./odin: free(): invalid pointer: 0xbfba4444 ***
======= Backtrace: =========
/lib/tls/i686/cmov/libc.so.6(+0x6b161)[0xb75f9161]
/lib/tls/i686/cmov/libc.so.6(+0x6c9b8)[0xb75fa9b8]
/lib/tls/i686/cmov/libc.so.6(cfree+0x6d)[0xb75fda9d]
/usr/lib/libstdc++.so.6(_ZdlPv+0x1f)[0xb77da2ef]

All well and good, but other cases when things crash, I’ve been doing backtrace() and then using a system call to addr2line and printing the actual points in the function instead. But when it’s a glibc crash, it quits bypassing any signal handlers I called.

Is there a way to hook against these glibc crashes?

Answer 1

That is an option for memory functions, you can toggle it using mallopt. By the sounds of it you want to set M_CHECK_ACTION to zero to allow execution to continue, unless you want the program to exit straight away in which case see if 2 allows you to do what you want.

This small program produces the normal glibc error: test1.c
This one ignores the error and carries on: test2.c
This one aborts on the error: test3.c