re PR c/79983 (Improve enum and struct redefinition diagnostic)

	PR c/79983
	* c-decl.c (start_struct): Use the location of TYPE_STUB_DECL of
	ref.
	(start_enum): Use the location of TYPE_STUB_DECL of enumtype.

	* gcc.dg/pr79983.c: New test.

From-SVN: r248927

gcc/c/ChangeLog

+2017-06-06  Marek Polacek  <polacek@redhat.com>
+
+	PR c/79983
+	* c-decl.c (start_struct): Use the location of TYPE_STUB_DECL of
+	ref.
+	(start_enum): Use the location of TYPE_STUB_DECL of enumtype.
+
 2017-06-02  Bernd Edlinger  <bernd.edlinger@hotmail.de>
 
 	* c-parser.c (c_parser_binary_expression): Implement the

gcc/c/c-decl.c

@@ -7453,6 +7453,9 @@ start_struct (location_t loc, enum tree_code code, tree name,
     ref = lookup_tag (code, name, true, &refloc);
   if (ref && TREE_CODE (ref) == code)
     {
+      if (TYPE_STUB_DECL (ref))
+	refloc = DECL_SOURCE_LOCATION (TYPE_STUB_DECL (ref));
+
       if (TYPE_SIZE (ref))
 	{
 	  if (code == UNION_TYPE)
@@ -8185,7 +8188,10 @@ start_enum (location_t loc, struct c_enum_contents *the_enum, tree name)
   /* Update type location to the one of the definition, instead of e.g.
      a forward declaration.  */
   else if (TYPE_STUB_DECL (enumtype))
-    DECL_SOURCE_LOCATION (TYPE_STUB_DECL (enumtype)) = loc;
+    {
+      enumloc = DECL_SOURCE_LOCATION (TYPE_STUB_DECL (enumtype));
+      DECL_SOURCE_LOCATION (TYPE_STUB_DECL (enumtype)) = loc;
+    }
 
   if (C_TYPE_BEING_DEFINED (enumtype))
     error_at (loc, "nested redefinition of %<enum %E%>", name);

gcc/testsuite/ChangeLog

+2017-06-06  Marek Polacek  <polacek@redhat.com>
+
+	PR c/79983
+	* gcc.dg/pr79983.c: New test.
+
 2017-06-06  David S. Miller  <davem@davemloft.net>
 
 	* gcc.target/sparc/sparc-ret-3.c: New test.

gcc/testsuite/gcc.dg/pr79983.c

+/* PR c/79983 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+struct S;
+struct S { int i; }; /* { dg-message "originally defined here" } */
+struct S { int i, j; }; /* { dg-error "redefinition of 'struct S'" } */
+
+enum E;
+enum E { A, B, C }; /* { dg-message "originally defined here" } */
+enum E { D, F }; /* { dg-error "nested redefinition of 'enum E'|redeclaration of 'enum E'" } */
+
+union U;
+union U { int i; }; /* { dg-message "originally defined here" } */
+union U { int i; double d; }; /* { dg-error "redefinition of 'union U'" } */