objective c - The signature of BOOL in a swift closure is wrong in a 32-bit iOS device

Question

The BOOL's signature is "B" normally in objective-c, Reference.

But on a 32-bit device. BOOL's signature is "c". Reference

Interesting finding

The interesting thing is that the BOOL in a swift closure is "B" on a 32-bit device (Should be "c").

For example, this is a swift closure.

let closure = {_ in        
} as @convention(block) (Bool) -> Void

The closure's signature is v8@?0B4 on 32-bit device. By right it should be v8@?0c4.

How to verify it?

sh_blockSignature(c code) is the function to get the signature from a block

test.m

enum {
    // Set to true on blocks that have captures (and thus are not true
    // global blocks) but are known not to escape for various other
    // reasons. For backward compatibility with old runtimes, whenever
    // BLOCK_IS_NOESCAPE is set, BLOCK_IS_GLOBAL is set too. Copying a
    // non-escaping block returns the original block and releasing such a
    // block is a no-op, which is exactly how global blocks are handled.
    BLOCK_IS_NOESCAPE      =  (1 << 23),
    
    BLOCK_HAS_COPY_DISPOSE =  (1 << 25),
    BLOCK_HAS_CTOR =          (1 << 26), // helpers have C++ code
    BLOCK_IS_GLOBAL =         (1 << 28),
    BLOCK_HAS_STRET =         (1 << 29), // IFF BLOCK_HAS_SIGNATURE
    BLOCK_HAS_SIGNATURE =     (1 << 30),
};

struct Block_literal_1 {
    void *isa; // initialized to &_NSConcreteStackBlock or &_NSConcreteGlobalBlock
    int flags;
    int reserved;
    void (*invoke)(void *, ...);
    struct Block_descriptor_1 {
        unsigned long int reserved;         // NULL
        unsigned long int size;         // sizeof(struct Block_literal_1)
        // optional helper functions
        void (*copy_helper)(void *dst, void *src);     // IFF (1<<25)
        void (*dispose_helper)(void *src);             // IFF (1<<25)
        // required ABI.2010.3.16
        const char *signature;                         // IFF (1<<30)
    } *descriptor;
    // imported variables
};

const char * _Nullable sh_blockSignature(id block)
{
    struct Block_literal_1 *layout = (__bridge void *)block;
    if (!(layout->flags & BLOCK_HAS_SIGNATURE))
        return nil;
    
    void *descRef = layout->descriptor;
    descRef += 2 * sizeof(unsigned long int);
    
    if (layout->flags & BLOCK_HAS_COPY_DISPOSE)
        descRef += 2 * sizeof(void *);
    
    if (!descRef) return nil;
    
    const char *signature = (*(const char **)descRef);
    return signature;
}

test2.swift

let closure = {_ in 
} as @convention(block) (Bool) -> Void
let p = sh_blockSignature(closure)!
let signature = String.init(cString: p)  
print(signature)  // "v8@?0B4"

Is this a swift bug on 32-bit device?

Answer 1

等待大神答复