Simon 'corecode' Schubert wrote: > Johannes Hofmann wrote: >> Hello, >> >> I see crashes with a string handling library on DragonFly. >> The problem can be reduced to the test program below. It crashes on >> DragonFly when compiled with "gcc -O2 -o foo foo.c". Without -O2 it >> runs fine. No problems on Linux with or without -O2. >> Can anyone spot the problem? I think its related to the use of >> va_copy(). > > No, the problem is that gcc uses %ebx after a function call, which it is > not allowed to do: [snip] > Or does the ABI dictate that %ebx needs to be restored? Seems that > linux/glibc doesn't clobber ebx.
okay, I am wrong here. %ebx is supposed to be saved and is also being saved by vsnprinf. gcc is good. So this is actually a case of stack smashing. Have fun finding the bug in vsnprintf or in your code :) > cheers > simon
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