[PATCH] Don't ICE on invalid weak decl (PR middle-end/67330)

[Marek Polacek]

Here we are ICEing on an invalid code: symtab_node::get asserts that it's
dealing with a function or a static or external variable, but an invalid
decl is rejected too late.  So don't try to mark_weak an invalid decl and
also don't duplicate the "declared weak after being used" check -- that is
already in mark_weak.
Perhaps we should also punt if (!TARGET_SUPPORTS_WEAK)?

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

2015-08-25  Marek Polacek  <pola...@redhat.com>

        PR middle-end/67330
        * varasm.c (declare_weak): Return after giving an error.

        * c-common.c (handle_weak_attribute): Don't check whether the
        visibility can be changed here.

        * gcc.dg/weak/weak-18.c: New test.

diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index ff502e5..7691035 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -8328,12 +8328,7 @@ handle_weak_attribute (tree *node, tree name,
       return NULL_TREE;
     }
   else if (VAR_OR_FUNCTION_DECL_P (*node))
-    {
-      struct symtab_node *n = symtab_node::get (*node);
-      if (n && n->refuse_visibility_changes)
-       error ("%+D declared weak after being used", *node);
-      declare_weak (*node);
-    }
+    declare_weak (*node);
   else
     warning (OPT_Wattributes, "%qE attribute ignored", name);
 
diff --git gcc/testsuite/gcc.dg/weak/weak-18.c 
gcc/testsuite/gcc.dg/weak/weak-18.c
index e69de29..ebeb4d5 100644
--- gcc/testsuite/gcc.dg/weak/weak-18.c
+++ gcc/testsuite/gcc.dg/weak/weak-18.c
@@ -0,0 +1,9 @@
+/* PR middle-end/67330 */
+/* { dg-do compile } */
+/* { dg-require-weak "" } */
+
+void
+f (void)
+{
+  __attribute__ ((weak)) int a; /* { dg-error "weak declaration of .a. must be 
public" } */
+}
diff --git gcc/varasm.c gcc/varasm.c
index 7fa2e7b..d9290a1 100644
--- gcc/varasm.c
+++ gcc/varasm.c
@@ -5403,7 +5403,10 @@ declare_weak (tree decl)
 {
   gcc_assert (TREE_CODE (decl) != FUNCTION_DECL || !TREE_ASM_WRITTEN (decl));
   if (! TREE_PUBLIC (decl))
-    error ("weak declaration of %q+D must be public", decl);
+    {
+      error ("weak declaration of %q+D must be public", decl);
+      return;
+    }
   else if (!TARGET_SUPPORTS_WEAK)
     warning (0, "weak declaration of %q+D not supported", decl);
 

        Marek