Re: pkg/47906: lang/g95: SEGV occurs when stack address is not aligned 8 bytes at main().

[NONAKA Kimihiro <nonakap%gmail.com@localhost>]

Hi,

2013/7/9 Joerg Sonnenberger <joerg%britannica.bec.de@localhost>:

>  > >Description:
>  > If the stack address is not aligned on 8 bytes, it is adjusted to 8 bytes 
> aligned at main().
>  > If stack address is adjusted, to get from the stack address the wrong 
> return address, SEGV occurs.
>
>  What happens if the whole section is dropped, i.e. the stack pointer
>  isn't adjusted in main at all? It shouldn't be needed at nothing on x86
>  requires 64bit alignment.

for speed.

g95-0.93/libf95.a-0.93/runtime/main.c:

 46 int main(int argc, char *argv[]) {
 47
 48 /* Sometimes on x86, the stack isn't aligned to an 8-byte boundary,
 49  * which kills performance associated with doubles.  Align if
 50  * unaligned. */
 51
 52 #if HAVE_REAL_10 == 1 || HAVE_REAL_10 == 2
 53     asm("mov %%esp, %%eax\n"
 54         "and $0x04, %%eax\n"
 55         "sub %%eax, %%esp\n" : : : "%eax");
 56 #endif

Regards,
--
NONAKA Kimihiro