[Bug middle-end/60797] [4.9 Regression] gcc hangs with error: only weak aliases are supported in this configuration

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60797

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
0x0000000000615b12 in c_write_global_declarations_1 (
    globals=<type_decl 0x7ffff6c4d170 int>)
    at /space/rguenther/src/svn/trunk/gcc/c/c-decl.c:10276
10272     do
10273       {
10274         reconsider = false;
10275         for (decl = globals; decl; decl = DECL_CHAIN (decl))
10276           reconsider |= wrapup_global_declaration_2 (decl);
10277       }
10278     while (reconsider);

which basically endlessly loops because nothing sets TREE_ASM_WRITTEN on
the alias.

Index: gcc/varasm.c
===================================================================
--- gcc/varasm.c        (revision 209292)
+++ gcc/varasm.c        (working copy)
@@ -5675,6 +5675,7 @@ assemble_alias (tree decl, tree target)
          else
            error_at (DECL_SOURCE_LOCATION (decl),
                      "only weak aliases are supported in this configuration");
+         TREE_ASM_WRITTEN (decl) = 1;
          return;
        }
 # endif

fixes it.  Probably also needed above for targets without any alias support.
I wonder why "weakref" errors just fall through and don't return though.

Index: gcc/varasm.c
===================================================================
--- gcc/varasm.c        (revision 209292)
+++ gcc/varasm.c        (working copy)
@@ -5665,6 +5665,7 @@ assemble_alias (tree decl, tree target)
 # if !defined(ASM_OUTPUT_WEAK_ALIAS) && !defined (ASM_WEAKEN_DECL)
       error_at (DECL_SOURCE_LOCATION (decl),
                "alias definitions not supported in this configuration");
+      TREE_ASM_WRITTEN (decl) = 1;
       return;
 # else
       if (!DECL_WEAK (decl))
@@ -5675,6 +5676,7 @@ assemble_alias (tree decl, tree target)
          else
            error_at (DECL_SOURCE_LOCATION (decl),
                      "only weak aliases are supported in this configuration");
+         TREE_ASM_WRITTEN (decl) = 1;
          return;
        }
 # endif