[C++ patch] Fix PR 57551

[C++ patch] Fix PR 57551

[Jan Hubicka]

Hi,
please see the PR log for details.  My symtab patch made testcase anon6.C to
fail because it tests that unused static var is output into the assembly and we
now optimize it out.

Adding attribute used however shows problem that the var suddenly becomes WEAK
and COMDAT. It seems to me that this is bug in C++ FE. Watchpointing the decl
I found that the decl is first correctly brought static by constrain_visibility
but later it is exported again by mark_decl_instantiated.

I think mark_decl_instantiated is wrong. I am not at all sure if the following
patch is proper fix though.

After this patch at least GCC agrees with clang on the testcase.

Bootstrapped/regtested x86_64-linux, OK?

Honza

	PR c++/57551
	* cp/pt.c (mark_decl_instantiated): Do not export explicit instantiations
	of anonymous namespace templates.

	* g++.dg/ext/visibility/anon6.C: Update testcase.

Index: cp/pt.c
===================================================================
--- cp/pt.c	(revision 199698)
+++ cp/pt.c	(working copy)
@@ -17402,6 +17402,13 @@ mark_decl_instantiated (tree result, int
   if (TREE_ASM_WRITTEN (result))
     return;
 
+  /* For anonymous namespace we don't need to do anything.  */
+  if (decl_anon_ns_mem_p (result))
+    {
+      gcc_assert (!TREE_PUBLIC (result));
+      return;
+    }
+
   if (TREE_CODE (result) != FUNCTION_DECL)
     /* The TREE_PUBLIC flag for function declarations will have been
        set correctly by tsubst.  */
Index: testsuite/g++.dg/ext/visibility/anon6.C
===================================================================
--- testsuite/g++.dg/ext/visibility/anon6.C	(revision 199698)
+++ testsuite/g++.dg/ext/visibility/anon6.C	(working copy)
@@ -1,6 +1,8 @@
 // PR c++/33094
 // { dg-final { scan-assembler "1BIiE1cE" } }
 // { dg-final { scan-assembler-not "globl.*1BIiE1cE" } }
+// { dg-final { scan-assembler-not "comdat" } }
+// { dg-final { scan-assembler-not "weak" } }
 // { dg-final { scan-assembler-not "1CIiE1cE" } }
 
 // Test that B<int>::c is emitted as an internal symbol, and C<int>::c is
@@ -18,7 +20,7 @@ namespace
   template <typename T>
   class B
   {
-    static const T c = 0;
+    __attribute__ ((__used__)) static const T c = 0;
   };
 
   template <typename T> const T B<T>::c;

Re: [C++ patch] Fix PR 57551

[Jason Merrill]

OK.

Jason