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Subject: [Bug target/102772] [12 regression] g++.dg/torture/pr80334.C FAILs
Date: Tue, 22 Mar 2022 17:00:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102772

--- Comment #17 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to ro@CeBiTec.Uni-Bielefeld.DE from comment #16)
> Same here:
>=20
> Program Headers:
>   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
> [...]
>   TLS            0x00c3d0 0x0806c3d0 0x00000000 0x00000 0x00024 RW  0x10

If both linkers reproduce the problem and the PT_TLS is 16-byte aligned
and thr.1 in it is at offset 0 (or multiple of 16), then I'd think that poi=
nts
to the dynamic linker.
The TLS transitions are performed by the linker.

> > But the question is if in
> > struct __attribute__((aligned (32))) S { long long buf[4]; };
> > __thread struct S s;
> > S *foo (void) { return &s; }
> > it won't return not properly 32-byte aligned pointer too (and is that i=
n all
> > threads or just some (initial vs. other threads)?
>=20
> I've wrapped that in a small test programming, calling foo both from the
> initial thread and a new one: in all cases, the return value from foo
> was 32-byte aligned as expected.

Perhaps the problem only shows when the PT_TLS size is not a multiple of the
alignment?  Or depends on other PT_TLS segments in shared libraries in the =
same
process.  The pointer2.f90 testcase will link against libgomp which uses TL=
S as
well.
So perhaps try:
struct __attribute__((aligned (16))) S { char buf[0x24]; };
__thread struct S s;
__attribute__((noipa)) S *foo (void) { return &s; }
int
main ()
{
  #pragma omp parallel
  __builtin_printf ("%p\n", foo ());
  return 0;
}
?=