OC中的Block基本结构

写如下的block声明代码:

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        void (^blockTest)(void) = ^{
            NSLog(@"hahha");
        };
        blockTest();
    }
    return 0;
}

经过xcrun -sdk iphoneos clang -arch arm64 -rewrite-objc main.m转成C++后，拿到如下关键代码:

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;
  }
};

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

static void __main_block_func_0(struct __main_block_impl_0 *__cself) {

            NSLog((NSString *)&__NSConstantStringImpl__var_folders_3q_7klqgj0j63z08zcx0skwjm500000gn_T_main_47560d_mi_0);
        }

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[]) {
    /* @autoreleasepool */ { __AtAutoreleasePool __autoreleasepool; 
        void (*blockTest)(void) = ((void (*)())&__main_block_impl_0((void *)__main_block_func_0, &__main_block_desc_0_DATA));
        ((void (*)(__block_impl *))((__block_impl *)blockTest)->FuncPtr)((__block_impl *)blockTest);
    }
    return 0;
}

可将main.m中的代码转为如下代码:

#import <Foundation/Foundation.h>

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;
};

struct __main_block_desc_0 {
  size_t reserved;
  size_t Block_size;
};

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        void (^block)(void) = ^{
            NSLog(@"hahha");
        };
        struct __main_block_impl_0 *blockStruct = (__bridge struct __main_block_impl_0 *)block;
        blockStruct->impl.FuncPtr;
    }
    return 0;
}