output.txt

2014-11-13 20:51:24.187 a.out[78021:7001297] int, immediate call of block
2014-11-13 20:51:24.188 a.out[78021:7001297] 42
2014-11-13 20:51:24.564 a.out[78025:7001307] int, block called after return
2014-11-13 20:51:24.565 a.out[78025:7001307] 42
2014-11-13 20:51:24.921 a.out[78029:7001313] NSString, immediate call of block
2014-11-13 20:51:24.922 a.out[78029:7001313] 42
2014-11-13 20:51:25.295 a.out[78033:7001323] NSString, block called after return
2014-11-13 20:51:25.297 a.out[78033:7001323] (null)

run.sh

cc -DINTS -DIMMEDIATECALL -Os -fobjc-arc -framework Foundation test.m && ./a.out
cc -DINTS                 -Os -fobjc-arc -framework Foundation test.m && ./a.out
cc        -DIMMEDIATECALL -Os -fobjc-arc -framework Foundation test.m && ./a.out
cc                        -Os -fobjc-arc -framework Foundation test.m && ./a.out
rm a.out

test.m

#import <Foundation/Foundation.h>
 
@interface Foo : NSObject
@property (readwrite, copy) void (^blockprop)();
@end

#if defined(INTS)
	typedef int error_t;
	static int _error = 42;
	static int *error = &_error;
	static inline void showerror(error_t *e)
	{
		NSLog(@"%d", *e);
	}
#else
	typedef NSString error_t;
	static NSString *error = @"42";
	static inline void showerror(error_t *e)
	{
		NSLog(@"%@", e);
	}
#endif

@implementation Foo
 
- (id)initWithError:(error_t **)errorHandle;
{
	self = [super init];
	if (self)
	{
		self.blockprop = ^{
			*errorHandle = error;
		};

#if defined(IMMEDIATECALL)
		self.blockprop();
#endif
	}
	return self;
}
 
@end
 
int main(int argc, const char * argv[])
{
	@autoreleasepool
	{
		NSLog(
			@"%s, %s",
#if defined(INTS)
			"int",
#else
			"NSString",
#endif
#if defined(IMMEDIATECALL)
			"immediate call of block"
#else
			"block called after return"
#endif
			);

		error_t *e = 0;
		Foo *foo = [[Foo alloc] initWithError:&e];
#if !defined(IMMEDIATECALL)
		foo.blockprop();
#endif
		showerror(e);
	}
	
    return 0;
}