[C++ PATCH] Only warn with -Wc++1z-compat about mangling of visible symbols

[Jakub Jelinek]

Hi!

It seems -Wabi/-Wc++1z-compat warns about mangling changes even for symbols 
that are
not visible outside of its TU (so likely only inline asm or tools
looking at .symtab STB_LOCAL symbols would notice).  Perhaps that is fine
for -Wabi that isn't enabled in -Wall/-Wextra, but -Wc++1z-compat is, and
I think most of the users don't really care about mangling of those symbols.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2016-11-10  Jakub Jelinek  <ja...@redhat.com>

        * mangle.c (mangle_decl): Only emit -Wc++1z-compat warnings for
        public or external symbols.

        * g++.dg/cpp1z/noexcept-type14.C: New test.
        * g++.dg/asan/asan_test.C: Remove -Wno-c++1z-compat from dg-options.

--- gcc/cp/mangle.c.jj  2016-11-09 23:55:59.000000000 +0100
+++ gcc/cp/mangle.c     2016-11-10 10:14:26.914059686 +0100
@@ -3836,7 +3836,8 @@ mangle_decl (const tree decl)
     }
   SET_DECL_ASSEMBLER_NAME (decl, id);
 
-  if (G.need_cxx1z_warning)
+  if (G.need_cxx1z_warning
+      && (TREE_PUBLIC (decl) || DECL_REALLY_EXTERN (decl)))
     warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wc__1z_compat,
                "mangled name for %qD will change in C++17 because the "
                "exception specification is part of a function type",
--- gcc/testsuite/g++.dg/cpp1z/noexcept-type14.C.jj     2016-11-10 
10:14:42.898857481 +0100
+++ gcc/testsuite/g++.dg/cpp1z/noexcept-type14.C        2016-11-10 
10:22:46.412741092 +0100
@@ -0,0 +1,26 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wall" }
+
+#define A asm volatile ("" : : : "memory")
+void foo () throw () {}
+extern void f1 (decltype (foo) *);     // { dg-bogus "mangled name" }
+void f2 (decltype (foo) *);            // { dg-bogus "mangled name" }
+extern void f3 (decltype (foo) *);     // { dg-warning "mangled name" "" { 
target c++14_down } }
+void f4 (decltype (foo) *);            // { dg-warning "mangled name" "" { 
target c++14_down } }
+void f5 (decltype (foo) *) { A; }      // { dg-warning "mangled name" "" { 
target c++14_down } }
+static void f6 (decltype (foo) *) { A; }// { dg-bogus "mangled name" }
+namespace N {
+void f7 (decltype (foo) *) { A; }      // { dg-warning "mangled name" "" { 
target c++14_down } }
+}
+namespace {
+void f8 (decltype (foo) *) { A; }      // { dg-bogus "mangled name" }
+}
+void bar ()
+{
+  f3 (foo);
+  f4 (foo);
+  f5 (foo);
+  f6 (foo);
+  N::f7 (foo);
+  f8 (foo);
+}
--- gcc/testsuite/g++.dg/asan/asan_test.C.jj    2016-11-10 00:00:00.000000000 
+0100
+++ gcc/testsuite/g++.dg/asan/asan_test.C       2016-11-10 13:28:55.348073019 
+0100
@@ -2,7 +2,7 @@
 // { dg-skip-if "" { *-*-* } { "*" } { "-O2" } }
 // { dg-skip-if "" { *-*-* } { "-flto" } { "" } }
 // { dg-additional-sources "asan_globals_test-wrapper.cc" }
-// { dg-options "-std=c++11 -fsanitize=address -fno-builtin -Wall 
-Wno-c++1z-compat -Werror -g -DASAN_UAR=0 -DASAN_HAS_EXCEPTIONS=1 
-DASAN_HAS_BLACKLIST=0 -DSANITIZER_USE_DEJAGNU_GTEST=1 -lasan -lpthread -ldl" }
+// { dg-options "-std=c++11 -fsanitize=address -fno-builtin -Wall -Werror -g 
-DASAN_UAR=0 -DASAN_HAS_EXCEPTIONS=1 -DASAN_HAS_BLACKLIST=0 
-DSANITIZER_USE_DEJAGNU_GTEST=1 -lasan -lpthread -ldl" }
 // { dg-additional-options "-DASAN_NEEDS_SEGV=1" { target { ! arm*-*-* } } }
 // { dg-additional-options "-DASAN_LOW_MEMORY=1 -DASAN_NEEDS_SEGV=0" { target 
arm*-*-* } }
 // { dg-additional-options "-DASAN_AVOID_EXPENSIVE_TESTS=1" { target { ! 
run_expensive_tests } } }

        Jakub