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From: "marxin at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/101726] target_clone resolver does not generate PIC
 despite -fPIC
Date: Wed, 11 Aug 2021 11:47:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101726

--- Comment #3 from Martin Li=C5=A1ka <marxin at gcc dot gnu.org> ---
So the solution won't be so easy. We generally face the problem that:
void    foo     (void)          __attribute__=20=20
((target_clones("avx512f,avx2,avx,default")));

is only a declaration. If we consider another TU with:

void
__attribute__   ((target_clones("avx512f,avx2,avx,default")))
foo     (void)
{
}

we end up with:

/tmp/cc5grfLD.o:pr101726.c:foo: error: undefined reference to 'foo.avx512f.=
0'
/tmp/cc5grfLD.o:pr101726.c:foo: error: undefined reference to 'foo.avx2.1'
/tmp/cc5grfLD.o:pr101726.c:foo: error: undefined reference to 'foo.avx.2'
/tmp/cc5grfLD.o:pr101726.c:foo: error: undefined reference to 'foo.default.=
3'

anyway. That's caused by the fact that target_clones are made local and so =
the
references are unresolved.
My suggestion would be simply doing a normal declaration:
void foo(void);

and doing target_clone definition in another TU. Doing that works would wor=
k.
That said, we should likely forbid target_clone declarations. Or do I miss
something?=