Address sanitizer squawkage

gistfile1.c

ken@Nepheli-20 /tmp> 
~/bin/clang/bin/clang -O3 -g -fsanitize=address -isysroot /Volumes/Data/Users/ken/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk -framework Foundation  /tmp/asanBarf.m 
ken@Nepheli-20 /tmp> ./a.out 
=================================================================
==91531==ERROR: AddressSanitizer: global-buffer-overflow on address 0x00010caf8f1f at pc 0x00010caf8dc2 bp 0x7fff531077a0 sp 0x7fff53107798
READ of size 32 at 0x00010caf8f1f thread T0
    #0 0x10caf8dc1  (/private/tmp/./a.out+0x100000dc1)
    #1 0x10caf8de4  (/private/tmp/./a.out+0x100000de4)
    #2 0x7fff8cdc25c8  (/usr/lib/system/libdyld.dylib+0x35c8)
    #3 0x0  (<unknown module>)

0x00010caf8f1f is located 24 bytes to the right of global variable '<string literal>' defined in '/tmp/asanBarf.m:48:33' (0x10caf8f00) of size 7
  '<string literal>' is ascii string 'hello!'
Shadow bytes around the buggy address:
  0x10002195f190: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002195f1a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002195f1b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002195f1c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002195f1d0: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9
=>0x10002195f1e0: 07 f9 f9[f9]f9 f9 f9 f9 00 00 00 00 00 00 00 00
  0x10002195f1f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002195f200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002195f210: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002195f220: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002195f230: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==91531==ABORTING



#import <Foundation/Foundation.h>
#import <simd/simd.h>

static inline CFIndex firstSetIndex(vector_char32 x) {
#if defined __AVX2__
    return __builtin_ctz(_mm256_movemask_epi8(x));
#else
    return __builtin_ctz(_mm_movemask_epi8(x.hi) << 16 | _mm_movemask_epi8(x.lo));
#endif
}

__attribute__((noinline)) Boolean __CFBytesInASCII_vec(const uint8_t *bytes, CFIndex len) {
    //  Early-out if length is zero.
    if (len == 0) return true;
    //  Back up to a 16-byte aligned memory location.
    const vector_char32 *aligned = (const vector_char32 *)((uintptr_t)bytes & -32);
    const size_t adjust = bytes - (const uint8_t *)aligned;
    //  Generate a mask to zero-out the first distance bytes of a vector.
    static const uint8_t maskSource[64] = {
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
        -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    };
    vector_char32 mask = *(const packed_char32 *)&maskSource[32 - adjust];
    //  Load the first vector and zero out any bytes preceeding the buffer we
    //  are actually interested in.  Adjust the length to account for these
    //  extra bytes as well.
    vector_char32 data = *aligned & mask;
    len += adjust;
    //  Now scan by aligned vectors until we either find a non-ASCII byte or
    //  we reach the end of the buffer.  This may read past the end of the
    //  buffer, but it will never cross a page boundary beyond the end of the
    //  buffer, so it is safe.
    while (!vector_any(data)) {
        if (len <= 32) return true;
        len -= 32;
        data = *++aligned;
    }
    //  We found a non-ASCII byte.  If its index in the vector is less than the
    //  remaining length, return fase.  Otherwise, return true.
    return firstSetIndex(data) >= len;
}


int main(int argc, const char * argv[]) {
	const char *shortStringBytes = "hello!";
	CFIndex shortLen = strlen(shortStringBytes);
	NSLog(@"%d", __CFBytesInASCII_vec((const uint8_t *)shortStringBytes, shortLen));
    return 0;
}