[Bug objc/7993] [3.4/3.5 regression] private variables cannot be shadowed in subclasses

["zack at codesourcery dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From zack at codesourcery dot com  2004-06-01 07:28 -------
Subject: 3.4/HEAD patches for PR 7993


PR 7993 (objc should allow shadowing private instance variables in
subclasses) has been hanging around for a long time now, mainly
because I thought the fix would be more work than "grab the patch out
of the PR and tweak it a little to fit on mainline."  I was wrong.
Appended is the patch - basically the same as the one Nicola Pero
wrote back in 2002 - I'm checking onto mainline and 3.4 branch.
Tested on i686-linux.

zw

2004-06-01  Nicola Pero  <nicola@brainstorm.co.uk>

 	PR objc/7993
        * objc-act.c (is_private): Do not emit the 'instance variable %s
        is declared private' error.
        (is_public): Emit the error after calling is_private.
        (lookup_objc_ivar): If the instance variable is private, return 0
        - the instance variable is invisible here.
testsuite:
        * objc.dg/private-1.m, objc-dg/private-2.m: New testcases.

===================================================================
Index: objc/objc-act.c
--- objc/objc-act.c	15 May 2004 23:07:53 -0000	1.214
+++ objc/objc-act.c	1 Jun 2004 05:28:46 -0000
@@ -6467,15 +6467,9 @@ is_ivar (tree decl_chain, tree ident)
 int
 is_private (tree decl)
 {
-  if (TREE_PRIVATE (decl)
-      && ! is_ivar (CLASS_IVARS (implementation_template), DECL_NAME (decl)))
-    {
-      error ("instance variable `%s' is declared private",
-	     IDENTIFIER_POINTER (DECL_NAME (decl)));
-      return 1;
-    }
-  else
-    return 0;
+  return (TREE_PRIVATE (decl)
+	  && ! is_ivar (CLASS_IVARS (implementation_template),
+			DECL_NAME (decl)));
 }
 
 /* We have an instance variable reference;, check to see if it is public.  */
@@ -6513,7 +6507,14 @@ is_public (tree expr, tree identifier)
 			   == CATEGORY_IMPLEMENTATION_TYPE))
 		      && (CLASS_NAME (objc_implementation_context)
 			  == OBJC_TYPE_NAME (basetype))))
-		return ! is_private (decl);
+		{
+		  int private = is_private (decl);
+
+		  if (private)
+		    error ("instance variable `%s' is declared private",
+			   IDENTIFIER_POINTER (DECL_NAME (decl)));
+		  return !private;
+		}
 
 	      /* The 2.95.2 compiler sometimes allowed C functions to access
 		 non-@public ivars.  We will let this slide for now...  */
@@ -9066,7 +9067,7 @@ lookup_objc_ivar (tree id)
   else if (objc_method_context && (decl = is_ivar (objc_ivar_chain, id)))
     {
       if (is_private (decl))
-	return error_mark_node;
+	return 0;
       else
         return build_ivar_reference (id);
     }
===================================================================
Index: testsuite/objc.dg/private-1.m
--- testsuite/objc.dg/private-1.m	1 Jan 1970 00:00:00 -0000
+++ testsuite/objc.dg/private-1.m	1 Jun 2004 05:28:47 -0000
@@ -0,0 +1,59 @@
+/* Test errors for accessing @private and @protected variables.  */
+/* Author: Nicola Pero <nicola@brainstorm.co.uk>.  */
+/* { dg-do compile } */
+#include <objc/objc.h>
+
+@interface MySuperClass
+{
+@private
+  int private;
+
+@protected
+  int protected;
+
+@public
+  int public;
+}
+- (void) test;
+@end
+
+@implementation MySuperClass
+- (void) test
+{
+  private = 12;   /* Ok  */
+  protected = 12; /* Ok  */
+  public = 12;    /* Ok  */
+}
+@end
+
+
+@interface MyClass : MySuperClass 
+@end
+
+@implementation MyClass
+- (void) test
+{
+  /* Private variables simply don't exist in the subclass.  */
+  private = 12;/* { dg-error "undeclared" } */
+  /* { dg-error "function it appears in" "" { target *-*-* } { 37 } } */
+
+  protected = 12; /* Ok  */
+  public = 12;    /* Ok  */
+}
+@end
+
+int main (void)
+{
+  MyClass *m = nil;
+  
+  if (m != nil)
+    {
+      int access;
+
+      access = m->private;   /* { dg-error "is @private" }  */
+      access = m->protected; /* { dg-error "is @protected" }  */
+      access = m->public;    /* Ok  */
+    }
+
+  return 0;
+}
===================================================================
Index: testsuite/objc.dg/private-2.m
--- testsuite/objc.dg/private-2.m	1 Jan 1970 00:00:00 -0000
+++ testsuite/objc.dg/private-2.m	1 Jun 2004 05:28:47 -0000
@@ -0,0 +1,54 @@
+/* Test warnings for shadowing instance variables.  */
+/* Author: Nicola Pero <nicola@brainstorm.co.uk>.  */
+/* { dg-do compile } */
+#include <objc/objc.h>
+
+@interface MySuperClass
+{
+@private
+  int private;
+
+@protected
+  int protected;
+
+@public
+  int public;
+}
+- (void) test;
+@end
+
+@implementation MySuperClass
+- (void) test
+{
+  /* FIXME: I wonder if the warnings shouldn't be better generated
+     when the variable is declared, rather than used!  */
+  int private = 12;
+  int protected = 12;
+  int public = 12;
+  int a;
+  
+  a = private;    /* { dg-warning "hides instance variable" } */
+  a = protected;  /* { dg-warning "hides instance variable" } */
+  a = public;     /* { dg-warning "hides instance variable" } */
+}
+@end
+
+
+@interface MyClass : MySuperClass 
+@end
+
+@implementation MyClass
+- (void) test
+{
+  int private = 12;
+  int protected = 12;
+  int public = 12;
+  int a;
+
+  /* The private variable can be shadowed without warnings, because
+   * it's invisible, and not accessible, to the subclass!  */
+  a = private;   /* Ok  */
+  a = protected; /* { dg-warning "hides instance variable" } */
+  a = public;    /* { dg-warning "hides instance variable" } */
+}
+@end


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=7993