diff mbox

[C++] PR 53184 ("Unnecessary anonymous namespace warnings")

Message ID 55DB143D.1010209@oracle.com
State New
Headers show

Commit Message

Paolo Carlini Aug. 24, 2015, 12:55 p.m. UTC 
Hi,

today I spent more time on this issue (which is getting duplicates). In 
fact it boils down to two separate issues:
1- Give a name to the warning, to make possible disabling it.
2- Don't talk about "anonymous namespace" when no anonymous namespace is 
involved.

Issue 1- should be rather straightforward, besides maybe the name 
itself: the below has Wsubobject-linkage. Makes sense?

Issue 2- seems slightly less trivial: the below first uses 
no_linkage_check and then falls back to the usual "anonymous namespace" 
message.

Tested x86_64-linux.

Thanks!
Paolo.

////////////////////
2015-08-24

	PR c++/53184
	* doc/invoke.texi ([Wsubobject-linkage]): Document.

/c-family
2015-08-24

	PR c++/53184
	* c.opt ([Wsubobject-linkage]): Add.

/cp
2015-08-24

	PR c++/53184
	* decl2.c (constrain_class_visibility): Use Wsubobject-linkage.

/testsuite
2015-08-24

	PR c++/53184
	* g++.dg/warn/Wsubobject-linkage-1.C: New.
	* g++.dg/warn/Wsubobject-linkage-2.C: Likewise.
	* g++.dg/warn/Wsubobject-linkage-3.C: Likewise.
	* g++.dg/warn/Wsubobject-linkage-4.C: Likewise.

Comments

Paolo Carlini Sept. 8, 2015, 8:23 p.m. UTC | #1 
Hi,

On 08/24/2015 02:55 PM, Paolo Carlini wrote:
> Hi,
>
> today I spent more time on this issue (which is getting duplicates). 
> In fact it boils down to two separate issues:
> 1- Give a name to the warning, to make possible disabling it.
> 2- Don't talk about "anonymous namespace" when no anonymous namespace 
> is involved.
>
> Issue 1- should be rather straightforward, besides maybe the name 
> itself: the below has Wsubobject-linkage. Makes sense?
>
> Issue 2- seems slightly less trivial: the below first uses 
> no_linkage_check and then falls back to the usual "anonymous 
> namespace" message.
Pinging this...

     https://gcc.gnu.org/ml/gcc-patches/2015-08/msg01411.html

Thanks,
Paolo.
Jason Merrill Sept. 9, 2015, 1 p.m. UTC | #2 
On 08/24/2015 08:55 AM, Paolo Carlini wrote:
> +		if (no_linkage_check (ftype, /*relaxed_p=*/false))

How about using the return value of no_linkage_check in the warning?

Jason
diff mbox

Patch

Index: c-family/c.opt
===================================================================
--- c-family/c.opt	(revision 227110)
+++ c-family/c.opt	(working copy)
@@ -944,6 +944,11 @@  Wuseless-cast
 C++ ObjC++ Var(warn_useless_cast) Warning
 Warn about useless casts
 
+Wsubobject-linkage
+C++ ObjC++ Var(warn_subobject_linkage) Warning Init(1)
+Warn if a class type has a base or a field whose type uses the anonymous
+namespace or depends on a type with no linkage
+
 ansi
 C ObjC C++ ObjC++
 A synonym for -std=c89 (for C) or -std=c++98 (for C++)
Index: cp/decl2.c
===================================================================
--- cp/decl2.c	(revision 227110)
+++ cp/decl2.c	(working copy)
@@ -2564,10 +2564,17 @@  constrain_class_visibility (tree type)
 
 	if (subvis == VISIBILITY_ANON)
 	  {
-	    if (!in_main_input_context ())
-	      warning (0, "\
+	    if (!in_main_input_context())
+	      {
+		if (no_linkage_check (ftype, /*relaxed_p=*/false))
+		  warning (OPT_Wsubobject_linkage, "\
+%qT has a field %qD whose type depends on a type with no linkage",
+		       type, t);
+		else
+		  warning (OPT_Wsubobject_linkage, "\
 %qT has a field %qD whose type uses the anonymous namespace",
 		       type, t);
+	      }
 	  }
 	else if (MAYBE_CLASS_TYPE_P (ftype)
 		 && vis < VISIBILITY_HIDDEN
@@ -2585,9 +2592,16 @@  constrain_class_visibility (tree type)
       if (subvis == VISIBILITY_ANON)
         {
 	  if (!in_main_input_context())
-	    warning (0, "\
+	    {
+	      if (no_linkage_check (TREE_TYPE (t), /*relaxed_p=*/false))
+		warning (OPT_Wsubobject_linkage, "\
+%qT has a base %qT whose type depends on a type with no linkage",
+			 type, TREE_TYPE (t));
+	      else
+		warning (OPT_Wsubobject_linkage, "\
 %qT has a base %qT whose type uses the anonymous namespace",
 		     type, TREE_TYPE (t));
+	    }
 	}
       else if (vis < VISIBILITY_HIDDEN
 	       && subvis >= VISIBILITY_HIDDEN)
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 227110)
+++ doc/invoke.texi	(working copy)
@@ -282,7 +282,7 @@  Objective-C and Objective-C++ Dialects}.
 -Wstrict-aliasing=n @gol -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
 -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{]} @gol
 -Wsuggest-final-types @gol -Wsuggest-final-methods -Wsuggest-override @gol
--Wmissing-format-attribute @gol
+-Wmissing-format-attribute -Wsubobject-linkage @gol
 -Wswitch  -Wswitch-default  -Wswitch-enum -Wswitch-bool -Wsync-nand @gol
 -Wsystem-headers  -Wtautological-compare  -Wtrampolines  -Wtrigraphs @gol
 -Wtype-limits  -Wundef @gol
@@ -4921,6 +4921,13 @@  types. @option{-Wconversion-null} is enabled by de
 Warn when a literal '0' is used as null pointer constant.  This can
 be useful to facilitate the conversion to @code{nullptr} in C++11.
 
+@item -Wsubobject-linkage @r{(C++ and Objective-C++ only)}
+@opindex Wsubobject-linkage
+@opindex Wno-subobject-linkage
+Warn if a class type has a base or a field whose type uses the anonymous
+namespace or depends on a type with no linkage.  This warning is
+enabled by default.
+
 @item -Wdate-time
 @opindex Wdate-time
 @opindex Wno-date-time
Index: testsuite/g++.dg/warn/Wsubobject-linkage-1.C
===================================================================
--- testsuite/g++.dg/warn/Wsubobject-linkage-1.C	(revision 0)
+++ testsuite/g++.dg/warn/Wsubobject-linkage-1.C	(working copy)
@@ -0,0 +1,9 @@ 
+// PR c++/53184
+
+typedef volatile struct { } Foo;
+
+#line 6 "foo.C"
+struct Bar { Foo foo; };   // { dg-warning "no linkage" }
+// { dg-bogus "anonymous namespace" "" { target *-*-* } 6 }
+struct Bar2 : Foo { };     // { dg-warning "no linkage" }
+// { dg-bogus "anonymous namespace" "" { target *-*-* } 8 }
Index: testsuite/g++.dg/warn/Wsubobject-linkage-2.C
===================================================================
--- testsuite/g++.dg/warn/Wsubobject-linkage-2.C	(revision 0)
+++ testsuite/g++.dg/warn/Wsubobject-linkage-2.C	(working copy)
@@ -0,0 +1,8 @@ 
+// PR c++/53184
+// { dg-options "-Wno-subobject-linkage" }
+
+typedef volatile struct { } Foo;
+
+#line 7 "foo.C"
+struct Bar { Foo foo; };
+struct Bar2 : Foo { };
Index: testsuite/g++.dg/warn/Wsubobject-linkage-3.C
===================================================================
--- testsuite/g++.dg/warn/Wsubobject-linkage-3.C	(revision 0)
+++ testsuite/g++.dg/warn/Wsubobject-linkage-3.C	(working copy)
@@ -0,0 +1,9 @@ 
+// PR c++/53184
+
+namespace { struct Foo { }; }
+
+#line 6 "foo.C"
+struct Bar { Foo foo; };   // { dg-warning "anonymous namespace" }
+// { dg-bogus "no linkage" "" { target *-*-* } 6 }
+struct Bar2 : Foo { };     // { dg-warning "anonymous namespace" }
+// { dg-bogus "no linkage" "" { target *-*-* } 8 }
Index: testsuite/g++.dg/warn/Wsubobject-linkage-4.C
===================================================================
--- testsuite/g++.dg/warn/Wsubobject-linkage-4.C	(revision 0)
+++ testsuite/g++.dg/warn/Wsubobject-linkage-4.C	(working copy)
@@ -0,0 +1,8 @@ 
+// PR c++/53184
+// { dg-options "-Wno-subobject-linkage" }
+
+namespace { struct Foo { }; }
+
+#line 7 "foo.C"
+struct Bar { Foo foo; };
+struct Bar2 : Foo { };