Update of bug #17647 (project hurd):
Status: None => In Progress
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Follow-up Comment #2:
I had a look today. But now I think I need Roland's or someone else's help.
The problem is --- so far --- only in `sysdeps/mach/hurd/i386/init-first.c'.
As soon as I compile that file with GCC 4.0 and everything else with GCC 4.1,
the resulting `libc.so' doesn't fail anymore. (I was only testing with a
primitive ``int main (void) { return 0; }'' so far, but that's already
something.)
So, what did I find. The problem may be related to this change:
#v+
2005-10-16 Roland McGrath <[EMAIL PROTECTED]>
[...]
[BZ #1253]
* sysdeps/mach/hurd/i386/init-first.c (init): Make cast kosher.
(_hurd_stack_setup): Don't declare with arguments and ellipsis.
Use __builtin_frame_address and __builtin_return_address.
(_dl_init_first): Likewise.
#v-
#v+
[...]
void
-_dl_init_first (int argc, ...)
+_dl_init_first (void)
{
first_init ();
- init (&argc);
+ init ((int *) __builtin_frame_address (0) + 2);
}
[...]
#v-
Now, experimenting a bit, there is a strange thing going on when using GCC
4.1 and `__builtin_frame_address':
Consider this test program:
#v+
#include <stdio.h>
void func (void)
{
int *ra = __builtin_return_address (0);
int *fa = __builtin_frame_address (0);
printf ("%s:fa[0] = %u\tfa[1] = %u\tra = %u\n", __func__, fa[0], fa[1],
ra);
}
int main (void)
{
int *ra = __builtin_return_address (0);
int *fa = __builtin_frame_address (0);
printf ("%s:fa = %u\tfa[1] = %u\tra = %u\n", __func__, fa, fa[1], ra);
func ();
}
#v-
#v+
$ gcc-4.0 test.c && ./a.out
main:fa = 3216472808 fa[1] = 3084724428 ra = 3084724428
func:fa[0] = 3216472808 fa[1] = 134513645 ra = 134513645
#v-
This is what I would expect. However:
#v+
main:fa = 3220364948 fa[1] = 3220365064 ra = 3085416652
func:fa[0] = 3220364952 fa[1] = 134513639 ra = 134513639
#v-
When applying optimizations via `-O' even the GCC 4.0 one produces unexpected
results, but that's due to function-inlining then, I guess.
So, perhaps there's something wrong with the usage of
`__builtin_frame_address' in `_dl_init_first'?
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