re PR other/4372 (#pragma weak pthread* inclusion causes applications to crash without a linker error when one forgets to link with -lpthread)

PR other/4372
* tree.h (IDENTIFIER_TRANSPARENT_ALIAS): New.
(TREE_DEPRECATED): Adjust comment.  Check for a DECL.
* c-common.c (handle_weakref_attribute): New.
(c_common_attribute_table): Add weakref.
* configure.ac (HAVE_GAS_WEAKREF): Check for weakref support
in the assembler.
* configure, config.in: Rebuilt.
* defaults.h (ASM_OUTPUT_WEAKREF): Define if HAVE_GAS_WEAKREF.
* doc/extend.texi: Document weakref attribute.
* varasm.c (ultimate_transparent_alias_target): New
(assemble_name): Use it.
(weak_finish_1): Split out of...
(weak_finish): ... and deal with weakrefs in...
(weakref_targets): ... new list.
(globalize_decl): Clean up weakref_targets.
(do_assemble_alias): Handle weakrefs.
(finish_aliases_1): Do not reject weakrefs to external symbols.
(assemble_alias): Handle weakrefs.

From-SVN: r106703

1 files changed, 41 insertions, 1 deletions

diff --git a/gcc/c-common.c b/gcc/c-common.c
index abd33d2..4501841 100644
--- a/gcc/c-common.c
+++ b/gcc/c-common.c
@@ -520,6 +520,7 @@ static tree handle_section_attribute (tree *, tree, tree, int, bool *);
 static tree handle_aligned_attribute (tree *, tree, tree, int, bool *);
 static tree handle_weak_attribute (tree *, tree, tree, int, bool *) ;
 static tree handle_alias_attribute (tree *, tree, tree, int, bool *);
+static tree handle_weakref_attribute (tree *, tree, tree, int, bool *) ;
 static tree handle_visibility_attribute (tree *, tree, tree, int,
 					 bool *);
 static tree handle_tls_model_attribute (tree *, tree, tree, int,
@@ -599,6 +600,8 @@ const struct attribute_spec c_common_attribute_table[] =
 			      handle_weak_attribute },
   { "alias",                  1, 1, true,  false, false,
 			      handle_alias_attribute },
+  { "weakref",                0, 1, true,  false, false,
+			      handle_weakref_attribute },
   { "no_instrument_function", 0, 0, true,  false, false,
 			      handle_no_instrument_function_attribute },
   { "malloc",                 0, 0, true,  false, false,
@@ -4742,7 +4745,10 @@ handle_alias_attribute (tree *node, tree name, tree args,
 	DECL_INITIAL (decl) = error_mark_node;
       else
 	{
-	  DECL_EXTERNAL (decl) = 0;
+	  if (lookup_attribute ("weakref", DECL_ATTRIBUTES (decl)))
+	    DECL_EXTERNAL (decl) = 1;
+	  else
+	    DECL_EXTERNAL (decl) = 0;
 	  TREE_STATIC (decl) = 1;
 	}
     }
@@ -4755,6 +4761,40 @@ handle_alias_attribute (tree *node, tree name, tree args,
   return NULL_TREE;
 }
 
+/* Handle a "weakref" attribute; arguments as in struct
+   attribute_spec.handler.  */
+
+static tree
+handle_weakref_attribute (tree *node, tree ARG_UNUSED (name), tree args,
+			  int flags, bool *no_add_attrs)
+{
+  tree attr = NULL_TREE;
+
+  /* The idea here is that `weakref("name")' mutates into `weakref,
+     alias("name")', and weakref without arguments, in turn,
+     implicitly adds weak. */
+
+  if (args)
+    {
+      attr = tree_cons (get_identifier ("alias"), args, attr);
+      attr = tree_cons (get_identifier ("weakref"), NULL_TREE, attr);
+
+      *no_add_attrs = true;
+    }
+  else
+    {
+      if (lookup_attribute ("alias", DECL_ATTRIBUTES (*node)))
+	error ("%Jweakref attribute must appear before alias attribute",
+	       *node);
+
+      attr = tree_cons (get_identifier ("weak"), NULL_TREE, attr);
+    }
+
+  decl_attributes (node, attr, flags);
+
+  return NULL_TREE;
+}
+
 /* Handle an "visibility" attribute; arguments as in
    struct attribute_spec.handler.  */