re PR c++/61825 (g++.dg/cpp0x/static_assert9.C FAILs)

	PR c++/61825
	* c-family/c-common.c (handle_alias_ifunc_attribute): Check
	that visibility change is possible
	(handle_weakref_attribute): Likewise.
	* cgraph.h (symtab_node): Add method get_create and
	field refuse_visibility_changes.
	(symtab_node::get_create): New method.
	* fold-const.c (tree_single_nonzero_warnv_p): Use get_create.
	* varasm.c (mark_weak): Verify that visibility change is
	possible.

	* gcc.dg/tree-ssa/nonzero-1.c: Require error to be output.

From-SVN: r215409

8 files changed, 80 insertions, 19 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 04db32a..c345dc1 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+2014-09-19  Jan Hubicka  <hubicka@ucw.cz>
+
+	PR c++/61825
+	* c-family/c-common.c (handle_alias_ifunc_attribute): Check
+	that visibility change is possible
+	(handle_weakref_attribute): Likewise.
+	* cgraph.h (symtab_node): Add method get_create and
+	field refuse_visibility_changes.
+	(symtab_node::get_create): New method.
+	* fold-const.c (tree_single_nonzero_warnv_p): Use get_create.
+	* varasm.c (mark_weak): Verify that visibility change is
+	possible.
+
 2014-09-19  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	* config/rs6000/predicates.md (fusion_gpr_mem_load): Move testing
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 39be956..818c32d 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -7757,6 +7757,19 @@ handle_alias_ifunc_attribute (bool is_alias, tree *node, tree name, tree args,
       *no_add_attrs = true;
     }
 
+  if (decl_in_symtab_p (*node))
+    {
+      struct symtab_node *n = symtab_node::get (decl);
+      if (n && n->refuse_visibility_changes)
+	{
+	  if (is_alias)
+	    error ("%+D declared alias after being used", decl);
+	  else
+	    error ("%+D declared ifunc after being used", decl);
+	}
+    }
+
+
   return NULL_TREE;
 }
 
@@ -7833,6 +7846,13 @@ handle_weakref_attribute (tree *node, tree ARG_UNUSED (name), tree args,
       DECL_WEAK (*node) = 1;
     }
 
+  if (decl_in_symtab_p (*node))
+    {
+      struct symtab_node *n = symtab_node::get (*node);
+      if (n && n->refuse_visibility_changes)
+	error ("%+D declared weakref after being used", *node);
+    }
+
   return NULL_TREE;
 }
 
diff --git a/gcc/cgraph.h b/gcc/cgraph.h
index 030a1c7..a316e40 100644
--- a/gcc/cgraph.h
+++ b/gcc/cgraph.h
@@ -346,6 +346,10 @@ public:
     return decl->decl_with_vis.symtab_node;
   }
 
+  /* Try to find a symtab node for declaration DECL and if it does not
+     exist or if it corresponds to an inline clone, create a new one.  */
+  static inline symtab_node * get_create (tree node);
+
   /* Return the cgraph node that has ASMNAME for its DECL_ASSEMBLER_NAME.
      Return NULL if there's no such node.  */
   static symtab_node *get_for_asmname (const_tree asmname);
@@ -394,7 +398,9 @@ public:
   unsigned analyzed : 1;
   /* Set for write-only variables.  */
   unsigned writeonly : 1;
-
+  /* Visibility of symbol was used for further optimization; do not
+     permit further changes.  */
+  unsigned refuse_visibility_changes : 1;
 
   /*** Visibility and linkage flags.  ***/
 
@@ -2519,4 +2525,12 @@ cgraph_node::mark_force_output (void)
   gcc_checking_assert (!global.inlined_to);
 }
 
+inline symtab_node * symtab_node::get_create (tree node)
+{
+  if (TREE_CODE (node) == VAR_DECL)
+    return varpool_node::get_create (node);
+  else
+    return cgraph_node::get_create (node);
+}
+
 #endif  /* GCC_CGRAPH_H  */
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index f7bf525..5cfc646 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -15850,7 +15850,7 @@ tree_single_nonzero_warnv_p (tree t, bool *strict_overflow_p)
 	  {
 	    struct symtab_node *symbol;
 
-	    symbol = symtab_node::get (base);
+	    symbol = symtab_node::get_create (base);
 	    if (symbol)
 	      return symbol->nonzero_address ();
 	    else
diff --git a/gcc/symtab.c b/gcc/symtab.c
index 792b3b5..9590fc8 100644
--- a/gcc/symtab.c
+++ b/gcc/symtab.c
@@ -1811,9 +1811,9 @@ bool
 symtab_node::nonzero_address ()
 {
   /* Weakrefs may be NULL when their target is not defined.  */
-  if (this->alias && this->weakref)
+  if (alias && weakref)
     {
-      if (this->analyzed)
+      if (analyzed)
 	{
 	  symtab_node *target = ultimate_alias_target ();
 
@@ -1828,7 +1828,7 @@ symtab_node::nonzero_address ()
 	     could be useful to eliminate the NULL pointer checks in LTO
 	     programs.  */
 	  if (target->definition && !DECL_EXTERNAL (target->decl))
-	    return true;
+	      return true;
 	  if (target->resolution != LDPR_UNKNOWN
 	      && target->resolution != LDPR_UNDEF
 	      && flag_delete_null_pointer_checks)
@@ -1847,22 +1847,28 @@ symtab_node::nonzero_address ()
      Those are handled by later check for definition.
 
      When parsing, beware the cases when WEAK attribute is added later.  */
-  if (!DECL_WEAK (this->decl)
-      && flag_delete_null_pointer_checks
-      && symtab->state > PARSING)
-    return true;
+  if (!DECL_WEAK (decl)
+      && flag_delete_null_pointer_checks)
+    {
+      refuse_visibility_changes = true;
+      return true;
+    }
 
   /* If target is defined and not extern, we know it will be output and thus
      it will bind to non-NULL.
      Play safe for flag_delete_null_pointer_checks where weak definition maye
      be re-defined by NULL.  */
-  if (this->definition && !DECL_EXTERNAL (this->decl)
-      && (flag_delete_null_pointer_checks || !DECL_WEAK (this->decl)))
-    return true;
+  if (definition && !DECL_EXTERNAL (decl)
+      && (flag_delete_null_pointer_checks || !DECL_WEAK (decl)))
+    {
+      if (!DECL_WEAK (decl))
+        refuse_visibility_changes = true;
+      return true;
+    }
 
   /* As the last resort, check the resolution info.  */
-  if (this->resolution != LDPR_UNKNOWN
-      && this->resolution != LDPR_UNDEF
+  if (resolution != LDPR_UNKNOWN
+      && resolution != LDPR_UNDEF
       && flag_delete_null_pointer_checks)
     return true;
   return false;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 89c88eb..130c6a7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2014-09-19  Jan Hubicka  <hubicka@ucw.cz>
+
+	PR c++/61825
+	* gcc.dg/tree-ssa/nonzero-1.c: Require error to be output.
+
 2014-09-19  Andi Kleen  <ak@linux.intel.com>
 
 	* gcc.dg/pg-override.c: Only run on x86 Linux.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/nonzero-1.c b/gcc/testsuite/gcc.dg/tree-ssa/nonzero-1.c
index c79811b..52e4a9a 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/nonzero-1.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/nonzero-1.c
@@ -1,11 +1,8 @@
 /* { dg-do compile } */
-/* { dg-options "-O2 -fdump-tree-optimized" } */
-extern int a;
+/* { dg-options "-O2" } */
+extern int a; /* { dg-error "declared weak after being used" } */
 t()
 {
   return &a!=0;
 }
 extern int a __attribute__ ((weak));
-
-/* { dg-final { scan-tree-dump-not "return 1" "optimized"} } */
-/* { dg-final { cleanup-tree-dump "optimized" } } */
diff --git a/gcc/varasm.c b/gcc/varasm.c
index 111c657..dd3211a 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -5230,6 +5230,12 @@ output_constructor (tree exp, unsigned HOST_WIDE_INT size,
 static void
 mark_weak (tree decl)
 {
+  if (DECL_WEAK (decl))
+    return;
+
+  struct symtab_node *n = symtab_node::get (decl);
+  if (n && n->refuse_visibility_changes)
+    error ("%+D declared weak after being used", decl);
   DECL_WEAK (decl) = 1;
 
   if (DECL_RTL_SET_P (decl)