Patch for c/13801

Joseph S. Myers jsm@polyomino.org.uk
Tue Aug 3 19:02:00 GMT 2004


On Mon, 2 Aug 2004, Zack Weinberg wrote:

> > There are also some extra diagnostics for incompatible implicit
> > function declarations as part of making implicit function declarations
> > work properly if the previous declaration is out of scope.  For
> > discussion of that for incompatibly implicitly declaring a built-in
> > function, see <http://gcc.gnu.org/ml/gcc/2004-08/msg00021.html>.
> 
> Submit this change separately.  With regard to the incompatible
> declarations of built-ins, I agree with Geoff, and I'd add that you
> should not diagnose incompatible redeclarations of built-ins that are
> not covered by the currently selected standard.

Here is the provisional separate patch to add the warnings / errors
for incompatible implicit function declarations.

I have made no changes regarding built-in functions not in the current
standard, i.e. redeclaring them gets the mandatory warning.  Apart
from the question as to which function the user wants, for which such
a diagnostic seems entirely appropriate, this is consistent with the
warnings for (for example)

int imaxabs;

(declaring such explicitly as a different type of symbol), and
DECL_BUILT_IN_NONANSI (which allowed different types of built-in
functions to be distinguished) was removed some time ago.

Bootstrapped with no regressions on i686-pc-linux-gnu.

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

2004-08-03  Joseph S. Myers  <jsm@polyomino.org.uk>

	* c-decl.c (implicitly_declare): Diagnose incompatible implicit
	declarations.

testsuite:
2004-08-03  Joseph S. Myers  <jsm@polyomino.org.uk>

	* gcc.dg/redecl-5.c: New test.
	* gcc.dg/format/attr-6.c: Expect warning for implicit declaration
	of scanf.

diff -rupN GCC.orig/gcc/c-decl.c GCC.mid/gcc/c-decl.c
--- GCC.orig/gcc/c-decl.c	2004-07-31 17:18:48.000000000 +0000
+++ GCC.mid/gcc/c-decl.c	2004-08-03 08:53:42.000000000 +0000
@@ -2082,6 +2082,23 @@ implicitly_declare (tree functionid)
 	      implicit_decl_warning (functionid, decl);
 	      C_DECL_IMPLICIT (decl) = 1;
 	    }
+	  if (DECL_BUILT_IN (decl))
+	    {
+	      if (!comptypes (default_function_type, TREE_TYPE (decl)))
+		{
+		  warning ("incompatible implicit declaration of built-in"
+			   " function %qD", decl);
+		}
+	    }
+	  else
+	    {
+	      if (!comptypes (default_function_type, TREE_TYPE (decl)))
+		{
+		  error ("incompatible implicit declaration of function %qD",
+			 decl);
+		  locate_old_decl (decl, error);
+		}
+	    }
 	  bind (functionid, decl, current_scope,
 		/*invisible=*/false, /*nested=*/true);
 	  return decl;
diff -rupN GCC.orig/gcc/testsuite/gcc.dg/format/attr-6.c GCC.mid/gcc/testsuite/gcc.dg/format/attr-6.c
--- GCC.orig/gcc/testsuite/gcc.dg/format/attr-6.c	2001-10-02 07:07:23.000000000 +0000
+++ GCC.mid/gcc/testsuite/gcc.dg/format/attr-6.c	2004-08-01 21:08:51.000000000 +0000
@@ -18,4 +18,5 @@ void
 foo (const char *s, int *p)
 {
   scanf("%ld", p); /* { dg-warning "format" "implicit scanf" } */
+  /* { dg-warning "implicit" "implicit decl warning" { target *-*-* } 20 } */
 }
diff -rupN GCC.orig/gcc/testsuite/gcc.dg/redecl-5.c GCC.mid/gcc/testsuite/gcc.dg/redecl-5.c
--- GCC.orig/gcc/testsuite/gcc.dg/redecl-5.c	1970-01-01 00:00:00.000000000 +0000
+++ GCC.mid/gcc/testsuite/gcc.dg/redecl-5.c	2004-08-01 20:36:26.000000000 +0000
@@ -0,0 +1,19 @@
+/* Test for multiple declarations and composite types.  Diagnosis of
+   incompatible implicit declaration.  */
+/* Origin: Joseph Myers <jsm@polyomino.org.uk> */
+/* { dg-do compile } */
+/* { dg-options "-std=c89" } */
+
+void
+f (void)
+{
+  long z(); /* { dg-error "previous implicit declaration" } */
+}
+
+void
+g (void)
+{
+  z(); /* { dg-error "incompatible" } */
+  labs(1); /* { dg-warning "incompatible" } */
+  printf("x"); /* { dg-warning "incompatible" } */
+}



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