Candidate fix for g++.dg/bprob.exp regressions

[Zack Weinberg <zack at codesourcery dot com>]

This is a candidate fix for the g++.dg/bprob.exp regression produced
by my c-decl.c rewrite.  They are a three-way interaction effect.
coverage.c no longer calls pushdecl on its synthetic functions, so
they do not get a lang_specific structure attached to them.  But we
still (correctly) try to put out debug info for them.  dwarf2out.c
calls lang_hooks.decl_name to get the name of the decl for the debug
info.  In C++, that reuses the machinery for error message printing,
dump_function_name.  And that crashes if fed a declaration without a
lang_specific structure.

My fix is to make dump_function_name do something sensible instead of
crashing.  It might be preferable to address this by not using
lang_hooks.decl_name for anything but diagnostics; I don't know, nor
do I know what dwarf2out.c should do instead.  Anyway, this makes the
regressions go away; i686-linux bootstrap in progress, but I will wait
for comments before checking anything in.  cc:ing Gaby since he owns
the C++ diagnostic printer.

Is there a PR for this regression?

zw

cp:
        * error.c (dump_function_name): If T's DECL_LANG_SPECIFIC
        is null, just print the literal name and return.

===================================================================
Index: cp/error.c
--- cp/error.c	21 Mar 2004 23:55:02 -0000	1.248
+++ cp/error.c	28 Mar 2004 18:09:11 -0000
@@ -1134,6 +1134,17 @@ dump_function_name (tree t, int flags)
 {
   tree name = DECL_NAME (t);
 
+  /* We can get here with a decl that was synthesized by language-
+     independent machinery (e.g. coverage.c) in which case it won't
+     have a lang_specific structure attached and DECL_CONSTRUCTOR_P
+     will crash.  In this case it is safe just to print out the
+     literal name.  */
+  if (!DECL_LANG_SPECIFIC (t))
+    {
+      pp_tree_identifier (cxx_pp, name);
+      return;
+    }
+
   if (TREE_CODE (t) == TEMPLATE_DECL)
     t = DECL_TEMPLATE_RESULT (t);
 
@@ -1163,7 +1174,7 @@ dump_function_name (tree t, int flags)
   else
     dump_decl (name, flags);
 
-  if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t)
+  if (DECL_TEMPLATE_INFO (t)
       && !DECL_FRIEND_PSEUDO_TEMPLATE_INSTANTIATION (t)
       && (DECL_TEMPLATE_SPECIALIZATION (t)
 	  || TREE_CODE (DECL_TI_TEMPLATE (t)) != TEMPLATE_DECL