[gcc r12-9101] Fortran: diagnose USE associated symbols in COMMON blocks [PR108453]

[gcc r12-9101] Fortran: diagnose USE associated symbols in COMMON blocks [PR108453]

[Harald Anlauf]

https://gcc.gnu.org/g:936fdf056944989c49dc4fff399ca5dc0d0213ee

commit r12-9101-g936fdf056944989c49dc4fff399ca5dc0d0213ee
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Sat Jan 28 17:59:23 2023 +0100

    Fortran: diagnose USE associated symbols in COMMON blocks [PR108453]
    
    gcc/fortran/ChangeLog:
    
            PR fortran/108453
            * match.cc (gfc_match_common): A USE associated name shall not appear
            in a COMMON block (F2018:C8121).
    
    gcc/testsuite/ChangeLog:
    
            PR fortran/108453
            * gfortran.dg/common_27.f90: New test.
    
    (cherry picked from commit aba9ff8f30d4245294ea2583de1dc28f1c7ccf7b)

Diff:
---
 gcc/fortran/match.cc                    | 10 ++++++++++
 gcc/testsuite/gfortran.dg/common_27.f90 | 14 ++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/gcc/fortran/match.cc b/gcc/fortran/match.cc
index 205811bb969..673662e9087 100644
--- a/gcc/fortran/match.cc
+++ b/gcc/fortran/match.cc
@@ -5339,6 +5339,16 @@ gfc_match_common (void)
 		goto cleanup;
 	    }
 
+	  /* F2018:R874:  common-block-object is variable-name [ (array-spec) ]
+	     F2018:C8121: A variable-name shall not be a name made accessible
+	     by use association.  */
+	  if (sym->attr.use_assoc)
+	    {
+	      gfc_error ("Symbol %qs at %C is USE associated from module %qs "
+			 "and cannot occur in COMMON", sym->name, sym->module);
+	      goto cleanup;
+	    }
+
 	  /* Deal with an optional array specification after the
 	     symbol name.  */
 	  m = gfc_match_array_spec (&as, true, true);
diff --git a/gcc/testsuite/gfortran.dg/common_27.f90 b/gcc/testsuite/gfortran.dg/common_27.f90
new file mode 100644
index 00000000000..dcde5de2bd2
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/common_27.f90
@@ -0,0 +1,14 @@
+! { dg-do compile }
+! PR fortran/108453 - a use associated variable cannot occur in COMMON
+! Contributed by G.Steinmetz
+
+module m
+  type t
+  end type
+  real :: r
+end
+program p
+  use m, only: t, r
+  common t      ! { dg-error "USE associated from module" }
+  common /cm/ r ! { dg-error "USE associated from module" }
+end