Hi Rimvydas,
> Gesendet: Mittwoch, 15. Februar 2023 um 21:58 Uhr
> Von: "Rimvydas Jasinskas"
>
> On Tue, Feb 14, 2023 at 9:55 PM Harald Anlauf wrote:
> > >>> There is one thing I cannot test, which is the handling of weak symbols
> > >>> on other platforms. A quick glance at the C testcases suggests that
> > >>> someone with access to either an NVPTX or MingGW target might tell
> > >>> whether that particular target should be excluded.
> While working on part 2 patch for weak variables I noticed that MingGW
> has quite different handling of weak symbols as weak externals between
> 32/64. I think adding "! { dg-skip-if "" { x86-64-*-mingw*} }" is
> needed to weak-1.f90 testcase, but I decided to wait for testsuite
> failure reports.
there are some MinGW users that will hopefully report back here soon.
> > > And, orthogonally: is '!GCC$ ATTRIBUTES weak' meant to be used only for
> > > subroutines (like in 'gfortran.dg/weak-1.f90') and also functions (I
> > > suppose; test case?), or also for weak "data" in some way (which, for
> > > example, in the C world then evaluates to a zero-address unless actually
> > > defined)?
> Weak zero-addressed "data" is more complicated between targets, I do
> not see a need for it.
> Functions are handled the same as subroutines, I had testcase for it,
> but decided to deal with fallout from weak-1.f90 first:
> $ cat gcc/testsuite/gfortran.dg/weak-2.f90
> ! { dg-do compile }
> ! { dg-require-weak "" }
> ! { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?impl" } }
> integer function impl()
> implicit none
> !GCC$ ATTRIBUTES weak :: impl
> end function
Yes, this works. I tried that before pushing.
> > Syntax and use of the WEAK directive.
> > !DIR$ WEAK procedure_name[, procedure_name] ...
> > !DIR$ WEAK procedure_name= stub_name[, procedure_name1= stub_name1] ...
> > stub_name
> > A stub procedure that exists in the code. The stub_name will be
> > called if a strong reference does not exist for procedure_name. The
> > stub_name procedure must have the same name and dummy argument list as
> > procedure_name.
> I think the same for procedure_name=stub_name can be achieved with
> bind(c,'sym') already without caring about symbol name mangling:
> $ cat gcc/testsuite/gfortran.dg/weak-6.f90
> ! { dg-do compile }
> ! { dg-require-weak "" }
> ! { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?bar__" } }
> integer function impl() bind(c,name='bar__')
> implicit none
> !GCC$ ATTRIBUTES weak :: impl
> end function
This does work indeed. It would be good to add these examples to
the documentation for reference in a subsequent patch.
> > I'm not sure whether we need to support weak symbols other than
> > procedures in gfortran. Maybe Rimvydas can comment on this.
> In 2nd part patch I was thinking to add support for weak global
> variables (like in modules):
> --- a/gcc/fortran/trans-decl.cc
> +++ b/gcc/fortran/trans-decl.cc
> @@ -814,6 +814,10 @@ gfc_finish_var_decl (tree decl, gfc_symbol * sym)
>&& (TREE_STATIC (decl) || DECL_EXTERNAL (decl)))
> set_decl_tls_model (decl, decl_default_tls_model (decl));
>
> + /* Mark weak variables. */
> + if (sym->attr.ext_attr & (1 << EXT_ATTR_WEAK))
> +declare_weak (decl);
> +
>gfc_finish_decl_attrs (decl, &sym->attr);
> }
>
> $ cat gcc/testsuite/gfortran.dg/weak-3.f90
> ! { dg-do compile }
> ! { dg-require-weak "" }
> ! { dg-skip-if "" { x86_64-*-mingw* } }
> ! { dg-skip-if "" { nvptx-*-* } }
> ! { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?__foo_MOD_abc" } }
> module foo
> implicit none
> !GCC$ ATTRIBUTES weak :: abc
> real :: abc(7)
> end module
>
> The catch is again scan-assembler issues with various symbol name
> manglings. Maybe just to add testcase without scan-assembler to check
> if testcase is not rejected?
Either that, or restricting those testcases by adding:
! { dg-skip-if "" { nvptx-*-* } }
! { dg-skip-if "" { x86_64-*-mingw* } }
> Currently already rejected are:
> $ cat gcc/testsuite/gfortran.dg/weak-4.f90
> ! { dg-do compile }
> ! { dg-require-weak "" }
> program foo ! { dg-error "weak declaration of 'foo' must be public" "" }
> implicit none
> !GCC$ ATTRIBUTES weak :: foo
> end program
Yes.
> $ cat gcc/testsuite/gfortran.dg/weak-9.f90
> ! { dg-do compile }
> ! { dg-require-weak "" }
> subroutine foo
> implicit none
> real :: abc ! { dg-error "weak declaration of 'abc' must be public" "" }
> !GCC$ ATTRIBUTES weak :: abc
> print *, abc
> contains
> subroutine bar ! { dg-error "weak declaration of 'bar' must be public" "" }
> !GCC$ ATTRIBUTES weak :: bar
> end subroutine
> end subroutine
>
> However error is not given if 'abc' is made a dummy argument or is not
> used, any ideas why?
At least for a dummy argument one can generate an error in
gfc_get_symbol_decl():
@@ -1549,6 +1552,14 @@ gfc_get_symbol_decl (gfc_symbol * sym)
|| (sym->module && sym->attr.if_source != IFSRC_DECL
&& sym->backend_decl));
+ if (sym->attr.dummy && (sym->attr
