Re: Question about message forwarding

[Issac Trotts]

Here is some more information that may be useful.  The crash happened
on a Gentoo Linux i686 box, using gcc version 3.3.5 and gnustep-base
1.10.3.  Adding a respondsToSelector method has no effect.

The same program runs fine under Cocoa:

ijtrotts@issac-trotts-powerbook-g4-15:~/downloads$ gcc
forwardingTest.m -framework Cocoa && ./a.out
Delegate 0x5042a0 foo
Delegate 0x5042a0 bar: 1234
Delegate 0x5042a0 baz: 1234


> Here is a test I wrote to track down a problem with message forwarding
> in another program I'm writing.
>
> // fowardingTest.m
> #import <Foundation/Foundation.h>
> #import <stdio.h>
>
> @interface Delegate: NSObject
> {
>
> }
> -(void)foo;
> -(void)bar:(int)key;
> -(void)baz:(NSNumber*)key;
> @end
>
> @implementation Delegate
> -(void)foo
> {
>     printf("Delegate %p foo\n",self);
> }
>
> -(void)bar:(int)key
> {
>     printf("Delegate %p bar: %i\n",self,key);
> }
>
> -(void)baz:(NSNumber*)key
> {
>     printf("Delegate %p baz: %i\n",self,[key intValue]);
> }
> @end
>
>
> @interface Forwarder: NSObject
> {
>     Delegate* delegate;
> }
> -(id)initWithDelegate:(Delegate*)d;
> @end
>
> @implementation Forwarder
> -(id)initWithDelegate:(Delegate*)d
> {
>     if((self=[super init])==nil) { return nil ; }
>     delegate = d;
>     return self;
> }
>
> -(void)forwardInvocation:(NSInvocation*)invo
> {
>     [invo invokeWithTarget:delegate];
> }
>
> -(NSMethodSignature *)methodSignatureForSelector:(SEL)sel
> {
>     return [delegate methodSignatureForSelector:sel];
> }
> @end
>
> int main()
> {
>     NSAutoreleasePool* pool = [NSAutoreleasePool new];
>     Delegate* d = [Delegate new];
>     Forwarder* f = [[Forwarder alloc] initWithDelegate:d];
>     [f foo];
>     [f bar:1234];
>     [f baz:[NSNumber numberWithInt:1234]];
>     [pool release];
>     return 0;
> }
>
>
> Here is the output:
>
> Delegate 0x8063bf0 foo
> Delegate 0x8063bf0 bar: -1078528424
> Segmentation fault
>
> So I would like to know why bar does not show 1234.  Looking at a
> stack trace, baz does get called, but I think the `key' argument is
> corrupted, hence the crash.  So, why are the args getting trashed?
>
> Thanks,
> Issac
>
>
>
>
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> End of Discuss-gnustep Digest, Vol 41, Issue 18
> ***********************************************
>