Fortran: avoid obsolescence warning for COMMON with submodule [PR111880]

gcc/fortran/ChangeLog:

	PR fortran/111880
	* resolve.cc (resolve_common_vars): Do not call gfc_add_in_common
	for symbols that are USE associated or used in a submodule.

gcc/testsuite/ChangeLog:

	PR fortran/111880
	* gfortran.dg/pr111880.f90: New test.

gcc/fortran/resolve.cc

@@ -986,8 +986,8 @@ resolve_common_vars (gfc_common_head *common_block, bool named_common)
 
       /* gfc_add_in_common may have been called before, but the reported errors
 	 have been ignored to continue parsing.
-	 We do the checks again here.  */
-      if (!csym->attr.use_assoc)
+	 We do the checks again here, unless the symbol is USE associated.  */
+      if (!csym->attr.use_assoc && !csym->attr.used_in_submodule)
 	{
 	  gfc_add_in_common (&csym->attr, csym->name, &common_block->where);
 	  gfc_notify_std (GFC_STD_F2018_OBS, "COMMON block at %L",

gcc/testsuite/gfortran.dg/pr111880.f90

@@ -0,0 +1,22 @@
+! { dg-do compile }
+! { dg-options "-std=f2018" }
+! PR fortran/111880 - redundant warning of obsolescent COMMON with submodule
+
+module third_party_module
+  integer :: some_param
+  common /not_my_code/ some_param   ! { dg-warning "COMMON block" }
+end module third_party_module
+
+module foo
+  use third_party_module
+  interface
+    module subroutine bar()
+    end subroutine bar
+  end interface
+end module foo
+
+submodule (foo) foo_submod      ! We do not need a warning here!
+contains
+  module procedure bar
+  end procedure bar
+end submodule foo_submod