Block相关

OC代码：

int main(int argc, const char * argv[]) {

    void (^blk)(void) = ^{
        printf("Block
");
    };
    
    blk();
    
    return 0;
}

通过Clang -rewrite-objc命令转成C语言代码：

struct __block_impl {
  void *isa;
  int Flags;
  int Reserved;
  void *FuncPtr;
};

struct __main_block_impl_0 {
    struct __block_impl impl;
    struct __main_block_desc_0* Desc;
    __main_block_impl_0(void *fp, struct __main_block_desc_0 *desc, int flags=0) {
        impl.isa = &_NSConcreteStackBlock;
        impl.Flags = flags;
        impl.FuncPtr = fp;
        Desc = desc;
    }
};

static void __main_block_func_0(struct __main_block_impl_0 *__cself) {
    printf("Block
");
}

static struct __main_block_desc_0 {
    size_t reserved;
    size_t Block_size;
} __main_block_desc_0_DATA = { 0, sizeof(struct __main_block_impl_0)};

int main(int argc, const char * argv[]) {

    void (*blk)(void) = ((void (*)())&__main_block_impl_0((void *)__main_block_func_0, &__main_block_desc_0_DATA));
    
    ((void (*)(__block_impl *))((__block_impl *)blk)->FuncPtr)((__block_impl *)blk);
    
    return 0;
}

可以看到整个Block结构如下：