On Wed, Jan 10, 2007 at 04:32:48PM -0700, Greg Watson wrote:
If the following code is compiled with 'gcc -g -O0 -o test test.c',
the address of argc is passed into func() in the ecx register. Since
ecx is not preserved after the call to printf(), the address of argc
is corrupted on return from func(). Normally this would not be a
problem, since argc is never used in the code.
This is a typical problem. There is not much that can be done about
it, although I remember once hearing a proposal that GCC should
forcibly extend the live ranges of local variables (or at least
arguments) at -O0 to improve debugging. That seems sensible to me.
Breakpoint 1, main (argc=1, argv=0xbffcef14) at test.c:14
12 func(&argc);
(gdb) n
in func
14 printf("hello\n");
(gdb) where
#0 main (argc=Cannot access memory at address 0x4
) at test.c:16
And honestly, I have no idea how that happened. Does it happen
with a current GDB? I suspect from the error message that this
one is not too recent.