Open Radar

 
Summary:
Parts before the dot in dot notation accessor calls runs twice

Reduced case:
#import <Foundation/Foundation.h>

@interface Foo : NSObject
{
@public;
	int callNo;
}
@property (readonly) int blah;
-(Foo*)mustNotRunTwice;
@end
@implementation Foo
-(Foo*)mustNotRunTwice;
{
	callNo++;
	NSLog(@"mustNotRunTwice called %d time%s.", callNo, (callNo==1)?"":"s");
	return self;
}
-(int)blah; { return 0; }
@end


int main (int argc, const char * argv[]) {
	Foo *foo = [Foo new];
	
	NSLog(@"Method accessor:");
	foo->callNo = 0;
	[[foo mustNotRunTwice] blah];
	
	NSLog(@"Dot accessor:");
	foo->callNo = 0;
	[foo mustNotRunTwice].blah;
	
    return 0;
}


Steps to Reproduce:
1. Compile the above as a Foundation tool

Expected Results:
2009-04-22 15:50:56.246 DotNotationBug[75608:10b] Method accessor:
2009-04-22 15:50:56.249 DotNotationBug[75608:10b] mustNotRunTwice called 1 time.
2009-04-22 15:50:56.250 DotNotationBug[75608:10b] Dot accessor:
2009-04-22 15:50:56.250 DotNotationBug[75608:10b] mustNotRunTwice called 1 time.

Actual Results:
2009-04-22 15:50:56.246 DotNotationBug[75608:10b] Method accessor:
2009-04-22 15:50:56.249 DotNotationBug[75608:10b] mustNotRunTwice called 1 time.
2009-04-22 15:50:56.250 DotNotationBug[75608:10b] Dot accessor:
2009-04-22 15:50:56.250 DotNotationBug[75608:10b] mustNotRunTwice called 1 time.
2009-04-22 15:50:56.251 DotNotationBug[75608:10b] mustNotRunTwice called 2 times.


Regression:
The bug appears fixed in GCC 4.2. 4.0 is however default in MacOS and a lot of developers are affected by this bug without knowing (imagine for example [foo autorelease].bar or [foo retain].bar). Also, 4.2 doesn't work on the iPhone as far as I know (and I use dot notation *a lot* in my iPhone apps, probably enough that this would affect performance if immediate steps are expensive).

Notes:
See also rdar://6671614