I'm on Win-XP (32bit, MSVC v16) and get a link error on a missing '__BitScanReverse64()' in test-count-leading-zeros.c:. Here is the dis-asm:
_count_leading_zeros_ll: push ebp mov ebp,esp sub esp,0x00000008 X$72: mov eax,dword ptr 0xc[ebp] push eax mov ecx,dword ptr 0x8[ebp] push ecx lea edx,-0x4[ebp] push edx call j^__BitScanReverse64 According to MSVC's <intrin.h>, the intrinsic for this function only exists on 64-bit machines: /*__MACHINEW64 : WIN64(tm), 64 bit compilers only */ __MACHINEW64(unsigned char _BitScanForward64(unsigned long* Index, unsigned __int64 Mask)) -- --gv