PR43651: add warning for duplicate qualifier

gcc/c/

	PR c/43651
	* c-decl.c (declspecs_add_qual): Warn when -Wduplicate-decl-specifier
	is enabled.
	* c-errors.c (pedwarn_c90): Return true if warned.
	* c-tree.h (pedwarn_c90): Change return type to bool.
	(enum c_declspec_word): Add new enumerator cdw_atomic.

gcc/

	PR c/43651
	* doc/invoke.texi (Wduplicate-decl-specifier): Document new option.

gcc/testsuite/

	PR c/43651
	* gcc.dg/Wduplicate-decl-specifier-c11.c: New test.
	* gcc.dg/Wduplicate-decl-specifier.c: Likewise.

gcc/c-family/

	PR c/43651
	* c.opt (Wduplicate-decl-specifier): New option.

From-SVN: r236142

4 files changed, 33 insertions, 3 deletions

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 7044400..d17cd92 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,12 @@
+2016-05-11  Mikhail Maltsev  <maltsevm@gmail.com>
+
+	PR c/43651
+	* c-decl.c (declspecs_add_qual): Warn when -Wduplicate-decl-specifier
+	is enabled.
+	* c-errors.c (pedwarn_c90): Return true if warned.
+	* c-tree.h (pedwarn_c90): Change return type to bool.
+	(enum c_declspec_word): Add new enumerator cdw_atomic.
+
 2016-05-11  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/71024
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 6ba0e0e..88424a7 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -9515,32 +9515,48 @@ declspecs_add_qual (source_location loc,
   gcc_assert (TREE_CODE (qual) == IDENTIFIER_NODE
 	      && C_IS_RESERVED_WORD (qual));
   i = C_RID_CODE (qual);
+  location_t prev_loc = 0;
   switch (i)
     {
     case RID_CONST:
       dupe = specs->const_p;
       specs->const_p = true;
+      prev_loc = specs->locations[cdw_const];
       specs->locations[cdw_const] = loc;
       break;
     case RID_VOLATILE:
       dupe = specs->volatile_p;
       specs->volatile_p = true;
+      prev_loc = specs->locations[cdw_volatile];
       specs->locations[cdw_volatile] = loc;
       break;
     case RID_RESTRICT:
       dupe = specs->restrict_p;
       specs->restrict_p = true;
+      prev_loc = specs->locations[cdw_restrict];
       specs->locations[cdw_restrict] = loc;
       break;
     case RID_ATOMIC:
       dupe = specs->atomic_p;
       specs->atomic_p = true;
+      prev_loc = specs->locations[cdw_atomic];
+      specs->locations[cdw_atomic] = loc;
       break;
     default:
       gcc_unreachable ();
     }
   if (dupe)
-    pedwarn_c90 (loc, OPT_Wpedantic, "duplicate %qE", qual);
+    {
+      bool warned = pedwarn_c90 (loc, OPT_Wpedantic,
+				 "duplicate %qE declaration specifier", qual);
+      if (!warned
+	  && warn_duplicate_decl_specifier
+	  && prev_loc >= RESERVED_LOCATION_COUNT
+	  && !from_macro_expansion_at (prev_loc)
+	  && !from_macro_expansion_at (loc))
+	warning_at (loc, OPT_Wduplicate_decl_specifier,
+		    "duplicate %qE declaration specifier", qual);
+    }
   return specs;
 }
 
diff --git a/gcc/c/c-errors.c b/gcc/c/c-errors.c
index d5e78b8..af157c0 100644
--- a/gcc/c/c-errors.c
+++ b/gcc/c/c-errors.c
@@ -71,11 +71,12 @@ pedwarn_c99 (location_t location, int opt, const char *gmsgid, ...)
    ISO C99 but not supported in ISO C90, thus we explicitly don't pedwarn
    when C99 is specified.  (There is no flag_c90.)  */
 
-void
+bool
 pedwarn_c90 (location_t location, int opt, const char *gmsgid, ...)
 {
   diagnostic_info diagnostic;
   va_list ap;
+  bool warned = false;
   rich_location richloc (line_table, location);
 
   va_start (ap, gmsgid);
@@ -92,6 +93,7 @@ pedwarn_c90 (location_t location, int opt, const char *gmsgid, ...)
 			       ? DK_PEDWARN : DK_WARNING);
 	  diagnostic.option_index = opt;
 	  report_diagnostic (&diagnostic);
+	  warned = true;
 	  goto out;
 	}
     }
@@ -114,7 +116,9 @@ pedwarn_c90 (location_t location, int opt, const char *gmsgid, ...)
       diagnostic_set_info (&diagnostic, gmsgid, &ap, &richloc, DK_PEDWARN);
       diagnostic.option_index = opt;
       report_diagnostic (&diagnostic);
+      warned = true;
     }
 out:
   va_end (ap);
+  return warned;
 }
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 07d0f65..d97e575 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -253,6 +253,7 @@ enum c_declspec_word {
   cdw_const,
   cdw_volatile,
   cdw_restrict,
+  cdw_atomic,
   cdw_saturating,
   cdw_alignas,
   cdw_address_space,
@@ -716,7 +717,7 @@ extern void c_bind (location_t, tree, bool);
 extern bool tag_exists_p (enum tree_code, tree);
 
 /* In c-errors.c */
-extern void pedwarn_c90 (location_t, int opt, const char *, ...)
+extern bool pedwarn_c90 (location_t, int opt, const char *, ...)
     ATTRIBUTE_GCC_DIAG(3,4);
 extern bool pedwarn_c99 (location_t, int opt, const char *, ...)
     ATTRIBUTE_GCC_DIAG(3,4);