Mainline merge as of 2002-09-15.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/tree-ssa-20020619-branch@57168 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 43 insertions, 5 deletions

diff --git a/libobjc/ChangeLog b/libobjc/ChangeLog
index db5a9386dfe..cd72694f810 100644
--- a/libobjc/ChangeLog
+++ b/libobjc/ChangeLog
@@ -1,3 +1,15 @@
+Thu Sep 12 12:44:37 2002  Nicola Pero  <n.pero@mi.flashnet.it>
+
+	* sendmsg.c (nil_method): Declare not to take a variable number of
+	args.
+	(objc_msg_lookup): Cast nil_method to IMP before returning it.
+	(objc_msg_lookup_super): The same.
+
+2002-09-10  Jan Hubicka  <jh@suse.cz>
+
+	* nil_method.c (nil_method): No longer defined with variable
+	arguments.
+
 2002-07-02  Rodney Brown  <rbrown64@csc.com.au>
 
 	* objc/encoding.h: Fix formatting.
diff --git a/libobjc/nil_method.c b/libobjc/nil_method.c
index 800b0e3bf53..5e37c4d5dfb 100644
--- a/libobjc/nil_method.c
+++ b/libobjc/nil_method.c
@@ -29,8 +29,27 @@ Boston, MA 02111-1307, USA.  */
 
 #include "runtime.h"
 
+/* When the receiver of a method invocation is nil, the runtime
+   returns nil_method() as the method implementation.  This function
+   will be casted to whatever function was supposed to be executed to
+   execute that method (that function will take an id, followed by a
+   SEL, followed by who knows what arguments, depends on the method),
+   and executed.
+   
+   For this reason, nil_method() should be a function which can be
+   called in place of any function taking an 'id' argument followed by
+   a 'SEL' argument, followed by zero, or one, or any number of
+   arguments (both a fixed number, or a variable number !).
+   
+   There is no "proper" implementation of such a nil_method function
+   in C, however in all existing implementations it does not matter
+   when extra arguments are present, so we can simply create a function
+   taking a receiver and a selector, and all other arguments will be
+   ignored. :-)
+*/
+
 id
-nil_method (id receiver, SEL op __attribute__ ((__unused__)), ...)
+nil_method (id receiver, SEL op __attribute__ ((__unused__)))
 {
   return receiver;
 }
diff --git a/libobjc/objc/objc.h b/libobjc/objc/objc.h
index 79b2519e576..699542c493b 100644
--- a/libobjc/objc/objc.h
+++ b/libobjc/objc/objc.h
@@ -73,7 +73,14 @@ typedef struct objc_object {
 
 /*
 ** Definition of method type.  When retrieving the implementation of a
-** method, this is type of the pointer returned
+** method, this is type of the pointer returned.  The idea of the
+** definition of IMP is to represent a 'pointer to a general function
+** taking an id, a SEL, followed by other unspecified arguments'.  You
+** must always cast an IMP to a pointer to a function taking the
+** appropriate, specific types for that function, before calling it -
+** to make sure the appropriate arguments are passed to it.  The code
+** generated by the compiler to perform method calls automatically
+** does this cast inside method calls.
 */
 typedef id (*IMP)(id, SEL, ...); 
 
diff --git a/libobjc/sendmsg.c b/libobjc/sendmsg.c
index 06fc9ba193e..6ef711b50d3 100644
--- a/libobjc/sendmsg.c
+++ b/libobjc/sendmsg.c
@@ -76,7 +76,7 @@ static id
 __objc_block_forward (id, SEL, ...);
 static Method_t search_for_method_in_hierarchy (Class class, SEL sel);
 Method_t search_for_method_in_list (MethodList_t list, SEL op);
-id nil_method (id, SEL, ...);
+id nil_method (id, SEL);
 
 /* Given a selector, return the proper forwarding implementation. */
 __inline__
@@ -197,7 +197,7 @@ objc_msg_lookup (id receiver, SEL op)
       return result;
     }
   else
-    return nil_method;
+    return (IMP)nil_method;
 }
 
 IMP
@@ -206,7 +206,7 @@ objc_msg_lookup_super (Super_t super, SEL sel)
   if (super->self)
     return get_imp (super->class, sel);
   else
-    return nil_method;
+    return (IMP)nil_method;
 }
 
 int method_get_sizeof_arguments (Method *);