使用Apple LLVM编译器时出现双重释放错误

Question

I have a project written for iOS 4.x. Recently i update it to iOS5 using XCode 4.3.2. It's strange that the app stop everytime with double free error when using Apple LLVM compiler. After i change back to LLVM GCC, it works fine. Is there any difference between this two? The code is shown below:

- (NSArray *)readCourselist {

    NSString *path = [[self currentUserPathString] stringByAppendingPathComponent:kUserCourseListFilename];

    return [NSArray arrayWithContentsOfFile:path];

}

- (NSArray *)getCourselist {

    NSArray *courseRawArray = [self readCourselist];

    for (NSDictionary *courseDic in courseRawArray) {

        CourseModel *courseModel = [[CourseModel alloc] init];

        courseModel.courseID = [[courseDic objectForKey:kKeyID] intValue];

        courseModel.courseNameString = [courseDic objectForKey:kKeyTitle];

        NSArray *lectureArray = [courseDic objectForKey:kKeyLecture];

        for (NSDictionary *lectureDic in lectureArray) {

            LectureModel *lectureModel = [[LectureModel alloc] init];

            NSString *startString = [lectureDic objectForKey:kKeyStart];


            if ([startString isEqualToString:@"8:00"]) {

                lectureModel.lectureNumber = 1;

            }

            else if ([startString isEqualToString:@"9:50"]) {

                lectureModel.lectureNumber = 2;

            }



            lectureModel.location = [lectureDic objectForKey:kKeyWhere];  //@property of location is retain

            [courseModel.lectureArray addObject:lectureModel];

            [lectureModel release];

        }

        [courseArray addObject:courseModel];

        [courseModel release];

    }

}

With more tracing i found out that it's

lectureModel.location = [lectureDic objectForKey:kKeyWhere];

that really matters. In my LectureModel, location is declared as follow

@property (nonatomic, retain) NSString *location;

@synthesize location;

- (id)init {
    location = NSLocalizedString(@"未知", nil);
}

Delete NSLocalizedString and everything works all right. Why?

Answer 1

Generally working with NSDictionary you want to use valueForKey: instead of objectForKey: , but I don't think that's the problem here. If you flip it back to LLVM, and run Instruments with "Zombies", it should point you to exactly where each free (well, release) is occurring.