ios 6 and 7 doesnt return same results

Question

It seems that our apps which use getPropertyType(..) are failing under ios7. For whatever reason, getPropertyType(..) on for example a NSString property returns NSString$'\x19\x03\x86\x13 as the type, instead of just NSString, and also instead of NSNumber it returns NSNumber\xf0\x90\xae\x04\xff\xff\xff\xff. All of this is causing some tricky problems when i later on check against a specific type. I have changed this (legacy?) code to use isKindOfClass instead, but it bothers me that I don't understand whats going on here.

The code in question:

#import <objc/runtime.h>

static const char *getPropertyType(objc_property_t property) {
    const char *attributes = property_getAttributes(property);
    char buffer[1 + strlen(attributes)];
    strcpy(buffer, attributes);
    char *state = buffer, *attribute;
    while ((attribute = strsep(&state, ",")) != NULL) {
        if (attribute[0] == 'T') {
            return (const char *)[[NSData dataWithBytes:(attribute + 3) length:strlen(attribute) - 4] bytes];
        }
    }
    return "@";
}

What on earth is going on, why are the results different??

Answer 1

The buffer returned by getPropertyType isn't NULL terminated. I think it's only dumb luck that it ever worked. Also, returning the data pointed to by a newly created NSData is not guaranteed to work once that function returns.

I'd make this return an NSString.

NSString* getPropertyType(objc_property_t property) {
    const char *attributes = property_getAttributes(property);
    char buffer[1 + strlen(attributes)];
    strcpy(buffer, attributes);
    char *state = buffer, *attribute;
    while ((attribute = strsep(&state, ",")) != NULL) {
        if (attribute[0] == 'T') {
            return [[NSString alloc] initWithBytes:attribute + 3 length:strlen(attribute) - 4 encoding:NSASCIIStringEncoding];
        }
    }
    return @"@";
}

This assumes ARC.