From d67bfe547589110a2d832fac7a8c8a2ca272c8b7 Mon Sep 17 00:00:00 2001 From: nicola Date: Thu, 12 Sep 2002 17:29:26 +0000 Subject: Added long comments on why nil_method takes the arguments it takes and how it's going to be used git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@57073 138bc75d-0d04-0410-961f-82ee72b054a4 --- libobjc/nil_method.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) (limited to 'libobjc') diff --git a/libobjc/nil_method.c b/libobjc/nil_method.c index 47201d69cc1..5e37c4d5dfb 100644 --- a/libobjc/nil_method.c +++ b/libobjc/nil_method.c @@ -29,10 +29,25 @@ Boston, MA 02111-1307, USA. */ #include "runtime.h" -/* nil_method is declared with variable arguments but the runtime calls it - in a way that does not setup the variable arguments correctly. Some Architectures - that have special arg calling conventions like x86-64 do need every function with - variable arguments called the correct way. */ +/* 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__))) { -- cgit v1.2.3