block_rewrite_in_cpp.mm

#import <Foundation/Foundation.h>

struct __block_impl;
struct __block_impl_0;

struct __block_impl {
    void *isa;
    int Flags;
    int Reserved;
    void (*FuncPtr)(__block_impl_0 *);
};

struct __block_impl_0 {
    struct __block_impl impl;
    struct __block_desc_0* Desc;
    int happy;

    __block_impl_0(void *fp, struct __block_desc_0 *desc, int _happy, int flags=0) : happy(_happy) {
        impl.isa = &_NSConcreteStackBlock;
        impl.Flags = flags;
        impl.FuncPtr = (void(*)(__block_impl_0 *))fp;
        Desc = desc;
    }
};

static struct __block_desc_0 {
  size_t reserved;
  size_t Block_size;
};

static void real_block_func(struct __block_impl_0 *__cself) {
    int happy = __cself->happy;
    NSLog(@"real_block_func: %d", happy);
}

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        int happy = 10;
        
        __block_desc_0 desc = {0, sizeof(__block_impl_0)};
        struct __block_impl_0 wrapper = __block_impl_0((void *) real_block_func, &desc, happy);

        happy = 20;

        wrapper.impl.FuncPtr(&wrapper);
    }

    return 0;
}