re PR c/17881 (Incomplete type warning is issued even for prototypes)

	PR c/17881
	* c-decl.c (grokparms): Don't warn for parameters of incomplete
	type in declarations that are not definitions except for the case
	of parameters of void type.

testsuite:
	* parm-incomplete-1.c: New test.

From-SVN: r88850

gcc/ChangeLog

+2004-10-10  Joseph S. Myers  <jsm@polyomino.org.uk>
+
+	PR c/17881
+	* c-decl.c (grokparms): Don't warn for parameters of incomplete
+	type in declarations that are not definitions except for the case
+	of parameters of void type.
+
 2004-10-10  Kazu Hirata  <kazu@cs.umass.edu>
 
 	* tree-cfg.c: Fix comment typos.

gcc/c-decl.c

@@ -4648,10 +4648,14 @@ grokparms (struct c_arg_info *arg_info, bool funcdef_flag)
       tree parm, type, typelt;
       unsigned int parmno;
 
-      /* If the arg types are incomplete in a declaration, they must
-	 include undefined tags.  These tags can never be defined in
-	 the scope of the declaration, so the types can never be
-	 completed, and no call can be compiled successfully.  */
+      /* If there is a parameter of incomplete type in a definition,
+	 this is an error.  In a declaration this is valid, and a
+	 struct or union type may be completed later, before any calls
+	 or definition of the function.  In the case where the tag was
+	 first declared within the parameter list, a warning has
+	 already been given.  If a parameter has void type, then
+	 however the function cannot be defined or called, so
+	 warn.  */
 
       for (parm = arg_info->parms, typelt = arg_types, parmno = 1;
 	   parm;
@@ -4675,13 +4679,13 @@ grokparms (struct c_arg_info *arg_info, bool funcdef_flag)
 		  TREE_VALUE (typelt) = error_mark_node;
 		  TREE_TYPE (parm) = error_mark_node;
 		}
-	      else
+	      else if (VOID_TYPE_P (type))
 		{
 		  if (DECL_NAME (parm))
-		    warning ("%Jparameter %u (%qD) has incomplete type",
+		    warning ("%Jparameter %u (%qD) has void type",
 			     parm, parmno, parm);
 		  else
-		    warning ("%Jparameter %u has incomplete type",
+		    warning ("%Jparameter %u has void type",
 			     parm, parmno);
 		}
 	    }

gcc/testsuite/ChangeLog

+2004-10-10  Joseph S. Myers  <jsm@polyomino.org.uk>
+
+	PR c/17881
+	* parm-incomplete-1.c: New test.
+
 2004-10-09  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/17867

gcc/testsuite/gcc.dg/parm-incomplete-1.c

+/* Test warnings and errors for incomplete parameter types.  Should
+   not be warned for in declarations that are not definitions: bug
+   17881.  Void types may be a special case, especially for unnamed
+   parameters and when qualified or with a storage class specifier;
+   see C90 6.5.4.3, DR#017 Q14, C90 TC1, DR#157, C99 J.2 (referencing
+   C99 6.7.5.3); the precise rules are unclear.  */
+/* Origin: Joseph Myers <jsm@polyomino.org.uk> */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+struct s;
+void f (struct s);
+void (*g)(struct s);
+struct t { void (*p)(struct s); };
+
+struct s { int b; };
+void h (struct s x) { }
+
+void j(struct t2); /* { dg-warning "warning: 'struct t2' declared inside parameter list" } */
+/* { dg-warning "its scope is only" "explanation" { target *-*-* } 19 } */
+
+union u;
+
+void v(union u x) { } /* { dg-error "error: parameter 1 \\('x'\\) has incomplete type" } */
+
+void p(void x); /* { dg-warning "warning: parameter 1 \\('x'\\) has void type" } */
+
+void q(const void x); /* { dg-warning "warning: parameter 1 \\('x'\\) has void type" } */