Hi,
per the audit trail, this issue appears to boil down to two separate issues:
- The warning doesn't appear universally useful, thus it would be nice
to give it a name in order to enable disabling it.
- As shown by the testcase, sometimes the wording is misleading: it
talks about 'anonymous namespace', where, as clarified by Jason in the
trail, the issue is really about a type with no linkage, no namespace
involved.
- The former is easy done, I picked: -Wsubobject-linkage. Makes sense?
- The latter is a little more tricky, because it doesn't seem always
easy to tell one case from the other, in particular when templates are
involved (eg, g++.dg/warn/anonymous-namespace-3.C) and the linkage issue
involves template arguments. Given that the warning doesn't seem
terribly important (as another data point, clang doesn't have it), so
far I have conditionals which reliably figure out cases of anonymous
namespace and cases of no linkage (per the testcase at issue, for
example) and otherwise fall back to an 'or' wording. I hope the
improvement is good enough. Alternately, I suppose the warning could use
a completely different, more generic, wording, but in that case
testcases like anonymous-namespace-3.C will need adjustment.
Tested x86_64-linux.
Thanks,
Paolo.
////////////////////////////
Index: c-family/c.opt
===================================================================
--- c-family/c.opt (revision 222822)
+++ c-family/c.opt (working copy)
@@ -913,6 +913,11 @@ 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 222822)
+++ cp/decl2.c (working copy)
@@ -2554,9 +2554,22 @@ constrain_class_visibility (tree type)
if (subvis == VISIBILITY_ANON)
{
if (!in_main_input_context ())
- warning (0, "\
+ {
+ if (MAYBE_CLASS_TYPE_P (ftype)
+ && decl_anon_ns_mem_p (TYPE_MAIN_DECL (ftype)))
+ warning (OPT_Wsubobject_linkage, "\
%qT has a field %qD whose type uses the anonymous namespace",
type, t);
+ else 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 or depends on a "
+ "type with no linkage",
+ type, t);
+ }
}
else if (MAYBE_CLASS_TYPE_P (ftype)
&& vis < VISIBILITY_HIDDEN
@@ -2574,9 +2587,21 @@ constrain_class_visibility (tree type)
if (subvis == VISIBILITY_ANON)
{
if (!in_main_input_context())
- warning (0, "\
+ {
+ if (decl_anon_ns_mem_p (TYPE_MAIN_DECL (TREE_TYPE (t))))
+ warning (OPT_Wsubobject_linkage, "\
%qT has a base %qT whose type uses the anonymous namespace",
- type, TREE_TYPE (t));
+ type, TREE_TYPE (t));
+ else 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 or depends on a "
+ "type with no linkage",
+ type, TREE_TYPE (t));
+ }
}
else if (vis < VISIBILITY_HIDDEN
&& subvis >= VISIBILITY_HIDDEN)
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi (revision 222822)
+++ doc/invoke.texi (working copy)
@@ -278,7 +278,7 @@ 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 -Wtrampolines -Wtrigraphs -Wtype-limits -Wundef @gol
-Wuninitialized -Wunknown-pragmas -Wno-pragmas @gol
@@ -4801,6 +4801,13 @@ 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 { };
