CrashReporter Info with Swizzle

//
//	Crashed Thread:  0  Dispatch queue: com.apple.main-thread
//
//	Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
//	Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000000
//
//	VM Regions Near 0:
//	--> 
//	__TEXT                 000000010d268000-000000010d26a000 [    8K] r-x/rwx SM=COW  /Users/USER/Library/Developer/Xcode/DerivedData/CrashSymbolTest-duwezzdulbkaqtffihfubuglwpki/Build/Products/Debug/CrashSymbolTest
//
//	Application Specific Information:
//	X identifier: seth
//
//	Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
//	0   CrashSymbolTest               	0x000000010d269aad -[X method] + 45 (main.m:33)
//	1   CrashSymbolTest               	0x000000010d269cfd __9+[Y load]_block_invoke + 189 (main.m:60)
//	2   CrashSymbolTest               	0x000000010d269dcb main + 171 (main.m:82)
//	3   libdyld.dylib                 	0x00007fff8be0f5fd start + 1
//

#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import <objc/message.h>


// See also: http://alastairs-place.net/blog/2013/01/10/interesting-os-x-crash-report-tidbits/

// We declare a symbol with a standard/convention name
static char *__crashreporter_info__ = 0;

// Mark the __crashreporter_info__ field as "referenced dynamically";
// This means it won’t get stripped and will be included in the resulting binary so the crash reporter can see it.
asm(".desc ___crashreporter_info__, 0x10");



@interface X : NSObject
@property (readwrite, retain) NSString * identifier;
@end



@implementation X

- (void)method
{
	NSLog(@"X method");
	
	int * x = NULL;
	*x = 3;
}

@end




@interface Y : X
@end

@interface Y (HackyHacky)
- (void)aq_hacky_hacky; // Shutty shutty up the compiler
@end

@implementation Y

+ (void)load;
{
	if ([self class] == [Y class]) {
		
		class_addMethod([X class], @selector(aq_hacky_hacky), imp_implementationWithBlock(^(X * instance){
			snprintf(__crashreporter_info__, 128, "X identifier: %s", instance.identifier.UTF8String);
			{
				IMP imp = class_getMethodImplementation([X class], @selector(aq_hacky_hacky)); // Gets the ORIGINAL method imp
				imp(instance, @selector(method));
			}
			__crashreporter_info__[0] = 0;
		}), @encode(void));
		
		Method origMethod = class_getInstanceMethod([X class], @selector(method));
        Method overrideMethod = class_getInstanceMethod([X class], @selector(aq_hacky_hacky));
		method_exchangeImplementations(origMethod, overrideMethod);
	}
}

@end




int main(int argc, const char * argv[])
{
	__crashreporter_info__ = calloc(128, 1);
	
	@autoreleasepool {
		X * x = [[X alloc] init];
		x.identifier = @"seth";
		[x method];
	}
    return 0;
}