/*
 * Copyright (c) 2014 - present Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#import <Foundation/Foundation.h>

@interface A : NSObject

@property int x;

+ (instancetype)sharedInstance;

@end

@implementation A {
}

+ (instancetype)sharedInstance
{
    static dispatch_once_t once;
    static id sharedInstance;
    dispatch_once(&once, ^{
        sharedInstance = [[self alloc] init];
    });
    return sharedInstance;
}

+ (instancetype)trans
{
    static id sharedInstance;
    void (^dummy_block)() = ^{
        sharedInstance = [[self alloc] init];
    };
    dummy_block();
    return sharedInstance;
}
@end

int main () {
    A *b = [A sharedInstance];
    int *p = 0;
    if (b == 0) return *p;
    else return 0;
}