[gcc r13-6338] Fortran: Add support for WEAK attribute for variables

[Harald Anlauf <anlauf@gcc.gnu.org>]

https://gcc.gnu.org/g:bcbeebc498126c50d73809ec8a4bd0bff27ee97b

commit r13-6338-gbcbeebc498126c50d73809ec8a4bd0bff27ee97b
Author: Rimvydas Jasinskas <rimvydas.jas@gmail.com>
Date:   Fri Feb 24 04:41:00 2023 +0000

    Fortran: Add support for WEAK attribute for variables
    
    Add the rest of the weak-*.f90 testcases.
    
    gcc/fortran/ChangeLog:
    
            * trans-decl.cc (gfc_finish_var_decl): Apply attribute.
            (generate_local_decl): Add diagnostic for dummy and local variables.
    
    gcc/testsuite/ChangeLog:
    
            * gfortran.dg/weak-2.f90: New test.
            * gfortran.dg/weak-3.f90: New test.
    
    Signed-off-by: Rimvydas Jasinskas <rimvydas.jas@gmail.com>

Diff:
---
 gcc/fortran/trans-decl.cc            | 14 ++++++++++++++
 gcc/testsuite/gfortran.dg/weak-2.f90 | 26 ++++++++++++++++++++++++++
 gcc/testsuite/gfortran.dg/weak-3.f90 | 30 ++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+)

diff --git a/gcc/fortran/trans-decl.cc b/gcc/fortran/trans-decl.cc
index ff64588b9a8..474920966ec 100644
--- 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);
 }
 
@@ -5885,6 +5889,16 @@ generate_local_decl (gfc_symbol * sym)
       if (!sym->attr.dummy && !sym->ns->proc_name->attr.entry_master)
 	generate_dependency_declarations (sym);
 
+      if (sym->attr.ext_attr & (1 << EXT_ATTR_WEAK))
+	{
+	  if (sym->attr.dummy)
+	    gfc_error ("Symbol %qs at %L has the WEAK attribute but is a "
+		       "dummy argument", sym->name, &sym->declared_at);
+	  else
+	    gfc_error ("Symbol %qs at %L has the WEAK attribute but is a "
+		       "local variable", sym->name, &sym->declared_at);
+	}
+
       if (sym->attr.referenced)
 	gfc_get_symbol_decl (sym);
 
diff --git a/gcc/testsuite/gfortran.dg/weak-2.f90 b/gcc/testsuite/gfortran.dg/weak-2.f90
new file mode 100644
index 00000000000..3e0e877e903
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/weak-2.f90
@@ -0,0 +1,26 @@
+! { dg-do compile }
+! { dg-require-weak "" }
+! { dg-skip-if "" { x86_64-*-mingw* } }
+! { dg-skip-if "" { nvptx-*-* } }
+
+! 1.
+! { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?__foo_MOD_abc" } }
+module foo
+implicit none
+!GCC$ ATTRIBUTES weak :: abc
+real :: abc(7)
+end module
+
+! 2.
+! { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?impl1" } }
+integer function impl1()
+implicit none
+!GCC$ ATTRIBUTES weak :: impl1
+end function
+
+! 3.
+! { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?bar__" } }
+integer function impl2() bind(c,name='bar__')
+implicit none
+!GCC$ ATTRIBUTES weak :: impl2
+end function
diff --git a/gcc/testsuite/gfortran.dg/weak-3.f90 b/gcc/testsuite/gfortran.dg/weak-3.f90
new file mode 100644
index 00000000000..cfa845921ff
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/weak-3.f90
@@ -0,0 +1,30 @@
+! { dg-do compile }
+! { dg-require-weak "" }
+
+! 1.
+program foo1  ! { dg-error "weak declaration of 'foo1' must be public" "" }
+implicit none
+!GCC$ ATTRIBUTES weak :: foo1
+end program
+
+! 2.
+subroutine foo2
+implicit none
+contains
+ function dar() ! { dg-error "weak declaration of 'dar' must be public" "" }
+ integer :: dar
+!GCC$ ATTRIBUTES weak :: dar
+ end function
+ subroutine bar ! { dg-error "weak declaration of 'bar' must be public" "" }
+!GCC$ ATTRIBUTES weak :: bar
+ end subroutine
+end subroutine
+
+! 3.
+subroutine foo3(n) ! { dg-error "has the WEAK attribute but is a dummy argument" "" }
+implicit none
+integer :: n
+!GCC$ ATTRIBUTES weak :: n
+real :: abc       ! { dg-error "has the WEAK attribute but is a local variable" "" }
+!GCC$ ATTRIBUTES weak :: abc
+end subroutine