block在内存中的分布

作者：Love@YR
链接：http://blog.csdn.net/jingqiu880905/article/details/50685683
请尊重原创，谢谢！

block 有三种类型 NSConcreteGlobalBlock、_NSConcreteStackBlock、_NSConcreteMallocBlock
分别存储在数据区，内存栈区，内存堆区
那么什么时候存储在哪个区上呢？我们看看下面的例子。

#import "ViewController.h"static NSString *globalStr=@"global";typedef int (^blk_t)(int);@interface ViewController (){}@end@implementation ViewController。。。省略- (IBAction)buttonTaped:(id)sender {    int *a2;     __block int b2;    b2=3;    a2=&b2;    static NSString *localStr=@"local";    //未引用外部变量即为NSGlobalBlock    blocakName bl1=^void(int a){        localStr=@"localstr1";//局部静态变量，通过指针传递        globalStr=@"globalStr1";//全局静态变量和全局变量，通过值传递        NSLog(@"a is %d,local str is %@,global str is %@",a,localStr,globalStr);    };    NSLog(@"bl1 is at %@",bl1);    blocakName bl2=^void(int a){        localStr=@"localstr1";//局部静态变量，通过指针传递        globalStr=@"globalStr1";//全局静态变量和全局变量，通过值传递        b2=6;//局部变量,b2需要__block修饰 不然只可读        NSLog(@"a is %d,a2 is %d,b2 is %d,local str is %@,global str is %@",a,*a2,b2,localStr,globalStr);    };    //引用了外部变量即为stack block，block的实现与上面的完全相同    NSLog(@"bl2 block is %@",^void(int a){        localStr=@"localstr1";//局部静态变量，通过指针传递        globalStr=@"globalStr1";//全局静态变量和全局变量，通过值传递        b2=6;//局部变量,b2需要__block修饰 不然只可读        NSLog(@"a is %d,a2 is %d,b2 is %d,local str is %@,global str is %@",a,*a2,b2,localStr,globalStr);    });    //引用了外部变量即为stackblock，arc下当引用此block变量时自动复制到堆上    NSLog(@"bl2 is %@",bl2);    bl1(5);//调用    bl2(10);//调用}@end

打印的结果：

bl1 is <__NSGlobalBlock__: 0x10f13c0d0>bl2 block is <__NSStackBlock__: 0x7fff50ac3078>bl2 is <__NSMallocBlock__: 0x7fc81bf21aa0>a is 5,local str is localstr1,global str is globalStr1a is 10,a2 is 3,b2 is 6,local str is localstr1,global str is globalStr1

参考：http://www.cnblogs.com/hanjun/p/3767394.html