re PR c/13728 (Duplicate parameter names not detected)

	PR 13728
	* c-decl.c (diagnose_mismatched_decls): Issue an error for two
	parameters with the same name, unless one is a forward decl.
	Do not issue a redundant-redeclaration warning for forward
	decls of parameters.
	* gcc.dg/decl-4.c: New testcase.

From-SVN: r78888

gcc/ChangeLog

+2004-03-03  Zack Weinberg  <zack@codesourcery.com>
+
+	PR 13728
+	* c-decl.c (diagnose_mismatched_decls): Issue an error for two
+	parameters with the same name, unless one is a forward decl.
+	Do not issue a redundant-redeclaration warning for forward
+	decls of parameters.
+
 2004-03-04  David Edelsohn  <edelsohn@gnu.org>
 
 	* doc/install.texi (*-ibm-aix*): Document use of Bash to speed up

gcc/c-decl.c

@@ -1211,8 +1211,18 @@ diagnose_mismatched_decls (tree newdecl, tree olddecl,
 	    }
 	}
     }
-  else /* VAR_DECL */
+  else /* PARM_DECL, VAR_DECL */
     {
+      /* Redeclaration of a PARM_DECL is invalid unless this is the
+	 real position of a forward-declared parameter (GCC extension).  */
+      if (TREE_CODE (newdecl) == PARM_DECL
+	  && (!TREE_ASM_WRITTEN (olddecl) || TREE_ASM_WRITTEN (newdecl)))
+	{
+	  error ("%Jredefinition of parameter '%D'", newdecl, newdecl);
+	  locate_old_decl (olddecl, error);
+	  return false;
+	}
+
       /* These bits are only type qualifiers when applied to objects.  */
       if (TREE_THIS_VOLATILE (newdecl) != TREE_THIS_VOLATILE (olddecl))
 	{
@@ -1244,7 +1254,10 @@ diagnose_mismatched_decls (tree newdecl, tree olddecl,
       && !(TREE_CODE (newdecl) == FUNCTION_DECL
 	   && DECL_INITIAL (newdecl) && !DECL_INITIAL (olddecl))
       /* Don't warn about an extern followed by a definition.  */
-    && !(DECL_EXTERNAL (olddecl) && !DECL_EXTERNAL (newdecl)))
+      && !(DECL_EXTERNAL (olddecl) && !DECL_EXTERNAL (newdecl))
+      /* Don't warn about forward parameter decls.  */
+      && !(TREE_CODE (newdecl) == PARM_DECL
+	   && TREE_ASM_WRITTEN (olddecl) && !TREE_ASM_WRITTEN (newdecl)))
     {
       warning ("%Jredundant redeclaration of '%D'", newdecl, newdecl);
       warned = true;

gcc/testsuite/ChangeLog

+2004-03-03  Zack Weinberg  <zack@codesourcery.com>
+
+	PR 13728
+	* gcc.dg/decl-4.c: New testcase.
+
 2004-03-03  Kazu Hirata  <kazu@cs.umass.edu>
 
 	* gcc.dg/torture/builtin-explog-1.c (PREC): Make it the same

gcc/testsuite/gcc.dg/decl-4.c

+/* Redeclaration of parameters is an error.  PR 13728.  */
+/* { dg-do compile } */
+
+void f (int fred,	/* { dg-error "previous definition" "" } */
+	int fred);	/* { dg-error "redefinition of parameter" "" } */
+
+void f2 (int fred,	/* { dg-error "previous definition" "" } */
+	 int fred)	/* { dg-error "redefinition of parameter" "" } */
+{
+}