Re: C, C++: Fix PR 69733 (bad location for ignored qualifiers warning)

[Bernd Schmidt <bschmidt@redhat.com>]

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On 06/22/2016 05:37 AM, Jeff Law wrote:
> It looks like this stalled...
>
> Anyway, it's fine for the trunk.

Some of the surrounding code was changed a bit to produce different 
errors for different C standards, so I had to make an adjustment to the 
patch. While I was here, I added cdw_atomic to the list of qualifiers to 
look for, and added a C-specific testcase for that case.

Retested as before. Ok for this version too?


Bernd

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c/
	PR c++/69733
	* c-decl.c (smallest_type_quals_location): New static function.
	(grokdeclarator): Try to find the correct location for an ignored
	qualifier.
cp/
	PR c++/69733
	* decl.c (grokdeclarator): Try to find the correct location for an
	ignored qualifier.
testsuite/
	PR c++/69733
	* c-c++-common/pr69733.c: New test.
	* gcc.dg/pr69733.c: New test.
	* gcc.target/i386/pr69733.c: New test.

Index: gcc/c/c-decl.c
===================================================================
--- gcc/c/c-decl.c	(revision 238040)
+++ gcc/c/c-decl.c	(working copy)
@@ -5463,6 +5463,27 @@ warn_defaults_to (location_t location, i
   va_end (ap);
 }
 
+/* Returns the smallest location != UNKNOWN_LOCATION in LOCATIONS,
+   considering only those c_declspec_words found in LIST, which
+   must be terminated by cdw_number_of_elements.  */
+
+static location_t
+smallest_type_quals_location (const location_t *locations,
+			      const c_declspec_word *list)
+{
+  location_t loc = UNKNOWN_LOCATION;
+  while (*list != cdw_number_of_elements)
+    {
+      location_t newloc = locations[*list];
+      if (loc == UNKNOWN_LOCATION
+	  || (newloc != UNKNOWN_LOCATION && newloc < loc))
+	loc = newloc;
+      list++;
+    }
+
+  return loc;
+}
+
 /* Given declspecs and a declarator,
    determine the name and type of the object declared
    and construct a ..._DECL node for it.
@@ -6277,7 +6298,19 @@ grokdeclarator (const struct c_declarato
 	       qualify the return type, not the function type.  */
 	    if (type_quals)
 	      {
-		int quals_used = type_quals;
+		const enum c_declspec_word ignored_quals_list[] =
+		  {
+		    cdw_const, cdw_volatile, cdw_restrict, cdw_address_space,
+		    cdw_atomic, cdw_number_of_elements
+		  };
+		location_t specs_loc
+		  = smallest_type_quals_location (declspecs->locations,
+						  ignored_quals_list);
+		if (specs_loc == UNKNOWN_LOCATION)
+		  specs_loc = declspecs->locations[cdw_typedef];
+		if (specs_loc == UNKNOWN_LOCATION)
+		  specs_loc = loc;
+
 		/* Type qualifiers on a function return type are
 		   normally permitted by the standard but have no
 		   effect, so give a warning at -Wreturn-type.
@@ -6287,13 +6320,14 @@ grokdeclarator (const struct c_declarato
 		   DR#423 means qualifiers (other than _Atomic) are
 		   actually removed from the return type when
 		   determining the function type.  */
+		int quals_used = type_quals;
 		if (flag_isoc11)
 		  quals_used &= TYPE_QUAL_ATOMIC;
 		if (quals_used && VOID_TYPE_P (type) && really_funcdef)
-		  pedwarn (loc, 0,
+		  pedwarn (specs_loc, 0,
 			   "function definition has qualified void return type");
 		else
-		  warning_at (loc, OPT_Wignored_qualifiers,
+		  warning_at (specs_loc, OPT_Wignored_qualifiers,
 			   "type qualifiers ignored on function return type");
 
 		/* Ensure an error for restrict on invalid types; the
Index: gcc/cp/decl.c
===================================================================
--- gcc/cp/decl.c	(revision 238040)
+++ gcc/cp/decl.c	(working copy)
@@ -10089,8 +10089,15 @@ grokdeclarator (const cp_declarator *dec
 	    if (type_quals != TYPE_UNQUALIFIED)
 	      {
 		if (SCALAR_TYPE_P (type) || VOID_TYPE_P (type))
-		  warning (OPT_Wignored_qualifiers,
-			   "type qualifiers ignored on function return type");
+		  {
+		    location_t loc;
+		    loc = smallest_type_quals_location (type_quals,
+							declspecs->locations);
+		    if (loc == UNKNOWN_LOCATION)
+		      loc = declspecs->locations[ds_type_spec];
+		    warning_at (loc, OPT_Wignored_qualifiers, "type "
+				"qualifiers ignored on function return type");
+		  }
 		/* We now know that the TYPE_QUALS don't apply to the
 		   decl, but to its return type.  */
 		type_quals = TYPE_UNQUALIFIED;
Index: gcc/testsuite/c-c++-common/pr69733.c
===================================================================
--- gcc/testsuite/c-c++-common/pr69733.c	(revision 0)
+++ gcc/testsuite/c-c++-common/pr69733.c	(working copy)
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-W -fdiagnostics-show-caret" } */
+
+typedef const double cd;
+double val;
+
+const double val0() {return val;} /* { dg-warning "qualifiers ignored" } */
+/* { dg-begin-multiline-output "" }
+ const double val0() {return val;}
+ ^~~~~
+{ dg-end-multiline-output "" } */
+
+volatile double val1() {return val;} /* { dg-warning "qualifiers ignored" } */
+/* { dg-begin-multiline-output "" }
+ volatile double val1() {return val;}
+ ^~~~~~~~
+{ dg-end-multiline-output "" } */
+
+cd val2() {return val;} /* { dg-warning "qualifiers ignored" } */
+/* { dg-begin-multiline-output "" }
+ cd val2() {return val;}
+ ^~
+{ dg-end-multiline-output "" } */
+
Index: gcc/testsuite/gcc.dg/pr69733.c
===================================================================
--- gcc/testsuite/gcc.dg/pr69733.c	(revision 0)
+++ gcc/testsuite/gcc.dg/pr69733.c	(working copy)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-W -fdiagnostics-show-caret" } */
+
+double val;
+
+_Atomic double val0() {return val;} /* { dg-warning "qualifiers ignored" } */
+/* { dg-begin-multiline-output "" }
+ _Atomic double val0() {return val;}
+ ^~~~~~~
+{ dg-end-multiline-output "" } */
+
Index: gcc/testsuite/gcc.target/i386/pr69733.c
===================================================================
--- gcc/testsuite/gcc.target/i386/pr69733.c	(revision 0)
+++ gcc/testsuite/gcc.target/i386/pr69733.c	(working copy)
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+/* { dg-options "-W -fdiagnostics-show-caret" } */
+
+typedef const double cd;
+double val;
+
+const double val0() {return val;} /* { dg-warning "qualifiers ignored" } */
+/* { dg-begin-multiline-output "" }
+ const double val0() {return val;}
+ ^~~~~
+{ dg-end-multiline-output "" } */
+
+volatile double val1() {return val;} /* { dg-warning "qualifiers ignored" } */
+/* { dg-begin-multiline-output "" }
+ volatile double val1() {return val;}
+ ^~~~~~~~
+{ dg-end-multiline-output "" } */
+
+cd val2() {return val;} /* { dg-warning "qualifiers ignored" } */
+/* { dg-begin-multiline-output "" }
+ cd val2() {return val;}
+ ^~
+{ dg-end-multiline-output "" } */
+
+__seg_fs int val3() {return val;} /* { dg-warning "qualifiers ignored" } */
+/* { dg-begin-multiline-output "" }
+ __seg_fs int val3() {return val;}
+ ^~~~~~~~
+{ dg-end-multiline-output "" } */
+