Patch for bug 23143

["Joseph S. Myers" <joseph at codesourcery dot com>]

This patch fixes bug 23143, parameter forward declarations being broken by 
the new C parser (and being such an obscure extension that no-one noticed 
for five months - the only parser problems reported before this related to 
handling of syntactically invalid code).  It adds tests for this extension 
(with those for the cases in bug 23144 being XFAILed - this patch just 
gets mainline back to the same state as 4.0 for this extension, the 
regressions from 3.4 are a separate matter).  Bootstrapped with no 
regressions on x86_64-unknown-linux-gnu.  Applied to mainline.

-- 
Joseph S. Myers               http://www.srcf.ucam.org/~jsm28/gcc/
    jsm@polyomino.org.uk (personal mail)
    joseph@codesourcery.com (CodeSourcery mail)
    jsm28@gcc.gnu.org (Bugzilla assignments and CCs)

2005-07-30  Joseph S. Myers  <joseph@codesourcery.com>

	PR c/23143
	* c-parser.c (c_parser_parms_list_declarator): Call
	mark_forward_parm_decls.
	* c-decl.c (merge_decls): Only check DECL_IN_SYSTEM_HEADER for
	decls with visibility structure.

testsuite:
2005-07-30  Joseph S. Myers  <joseph@codesourcery.com>

	PR c/23143
	* gcc.dg/parm-forwdecl-1.c, gcc.dg/parm-forwdecl-2.c,
	gcc.dg/parm-forwdecl-3.c, gcc.dg/parm-forwdecl-4.c: New tests.

diff -rupN GCC.orig/gcc/c-decl.c GCC/gcc/c-decl.c
--- GCC.orig/gcc/c-decl.c	2005-07-20 20:10:25.000000000 +0000
+++ GCC/gcc/c-decl.c	2005-07-29 23:20:57.000000000 +0000
@@ -1664,18 +1664,18 @@ merge_decls (tree newdecl, tree olddecl,
 	  && !C_DECL_BUILTIN_PROTOTYPE (olddecl)))
     DECL_SOURCE_LOCATION (newdecl) = DECL_SOURCE_LOCATION (olddecl);
 
-  /* Merge the unused-warning information.  */
-  if (DECL_IN_SYSTEM_HEADER (olddecl))
-    DECL_IN_SYSTEM_HEADER (newdecl) = 1;
-  else if (DECL_IN_SYSTEM_HEADER (newdecl))
-    DECL_IN_SYSTEM_HEADER (olddecl) = 1;
-
   /* Merge the initialization information.  */
    if (DECL_INITIAL (newdecl) == 0)
     DECL_INITIAL (newdecl) = DECL_INITIAL (olddecl);
 
    if (CODE_CONTAINS_STRUCT (TREE_CODE (olddecl), TS_DECL_WITH_VIS))
      {
+       /* Merge the unused-warning information.  */
+       if (DECL_IN_SYSTEM_HEADER (olddecl))
+	 DECL_IN_SYSTEM_HEADER (newdecl) = 1;
+       else if (DECL_IN_SYSTEM_HEADER (newdecl))
+	 DECL_IN_SYSTEM_HEADER (olddecl) = 1;
+
        /* Merge the section attribute.
 	  We want to issue an error if the sections conflict but that must be
 	  done later in decl_attributes since we are called before attributes
diff -rupN GCC.orig/gcc/c-parser.c GCC/gcc/c-parser.c
--- GCC.orig/gcc/c-parser.c	2005-06-29 22:09:40.000000000 +0000
+++ GCC/gcc/c-parser.c	2005-07-29 22:36:39.000000000 +0000
@@ -2463,6 +2463,7 @@ c_parser_parms_list_declarator (c_parser
 	{
 	  tree new_attrs;
 	  c_parser_consume_token (parser);
+	  mark_forward_parm_decls ();
 	  new_attrs = c_parser_attributes (parser);
 	  return c_parser_parms_list_declarator (parser, new_attrs);
 	}
diff -rupN GCC.orig/gcc/testsuite/gcc.dg/parm-forwdecl-1.c GCC/gcc/testsuite/gcc.dg/parm-forwdecl-1.c
--- GCC.orig/gcc/testsuite/gcc.dg/parm-forwdecl-1.c	1970-01-01 00:00:00.000000000 +0000
+++ GCC/gcc/testsuite/gcc.dg/parm-forwdecl-1.c	2005-07-29 22:30:28.000000000 +0000
@@ -0,0 +1,26 @@
+/* Test GNU parameter forward declarations.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+/* Valid uses.  */
+int f1(int a; int a);
+int f2(int a; int a) { return 0; }
+int f3(int a; int a; int a);
+int f4(int a; int a; int a) { return 0; }
+int f5(int a; int (*x)[a], int a);
+int f6(int a; int (*x)[a], int a) { return 0; }
+int f7(int a; int (*x)[a]; int (*y)[x[1][2]], int (*x)[a], int a);
+int f8(int a; int (*x)[a]; int (*y)[x[1][2]], int (*x)[a], int a) { return 0; }
+
+/* Strange uses accepted by GCC 4.0 but not by 3.4 and probably not
+   desirable to accept.  */
+int g1(int a;); /* { dg-error "just a forward declaration" "no parms" { xfail *-*-* } } */
+int g2(int a; __attribute__((unused))); /* { dg-error "just a forward declaration" "no parms" { xfail *-*-* } } */
+int g3(int;); /* { dg-error "just a forward declaration" "no parms" { xfail *-*-* } } */
+int g4(int, long;); /* { dg-error "just a forward declaration" "no parms" { xfail *-*-* } } */
+
+/* Invalid uses.  */
+int h1(int a; int b); /* { dg-error "just a forward declaration" } */
+int h2(int; int b); /* { dg-error "just a forward declaration" } */
+int h3(int a; long a); /* { dg-error "conflicting types|previous definition|just a forward declaration" } */
diff -rupN GCC.orig/gcc/testsuite/gcc.dg/parm-forwdecl-2.c GCC/gcc/testsuite/gcc.dg/parm-forwdecl-2.c
--- GCC.orig/gcc/testsuite/gcc.dg/parm-forwdecl-2.c	1970-01-01 00:00:00.000000000 +0000
+++ GCC/gcc/testsuite/gcc.dg/parm-forwdecl-2.c	2005-07-29 22:54:41.000000000 +0000
@@ -0,0 +1,8 @@
+/* Test GNU parameter forward declarations.  Warning with
+   -pedantic.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-pedantic" } */
+
+int f1(int a; int a); /* { dg-warning "warning: ISO C forbids forward parameter declarations" } */
+int f2(int a; int a) { return 0; } /* { dg-warning "warning: ISO C forbids forward parameter declarations" } */
diff -rupN GCC.orig/gcc/testsuite/gcc.dg/parm-forwdecl-3.c GCC/gcc/testsuite/gcc.dg/parm-forwdecl-3.c
--- GCC.orig/gcc/testsuite/gcc.dg/parm-forwdecl-3.c	1970-01-01 00:00:00.000000000 +0000
+++ GCC/gcc/testsuite/gcc.dg/parm-forwdecl-3.c	2005-07-29 22:54:46.000000000 +0000
@@ -0,0 +1,8 @@
+/* Test GNU parameter forward declarations.  Error with
+   -pedantic-errors.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-pedantic-errors" } */
+
+int f1(int a; int a); /* { dg-error "error: ISO C forbids forward parameter declarations" } */
+int f2(int a; int a) { return 0; } /* { dg-error "error: ISO C forbids forward parameter declarations" } */
diff -rupN GCC.orig/gcc/testsuite/gcc.dg/parm-forwdecl-4.c GCC/gcc/testsuite/gcc.dg/parm-forwdecl-4.c
--- GCC.orig/gcc/testsuite/gcc.dg/parm-forwdecl-4.c	1970-01-01 00:00:00.000000000 +0000
+++ GCC/gcc/testsuite/gcc.dg/parm-forwdecl-4.c	2005-07-29 22:56:04.000000000 +0000
@@ -0,0 +1,10 @@
+/* Test GNU parameter forward declarations.  OK with
+   -Wredundant-decls.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-Wredundant-decls" } */
+
+int f1(int a; int a);
+int f2(int a; int a) { return 0; }
+int f3(int a; int a; int a);
+int f4(int a; int a; int a) { return 0; }