#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
#include <string.h>
//#pragma function(strnlen_s) // disable [strnlen_s] intrinsic form, bug fixed
int main(void)
{
char str2[110] = "1234";
printf("len[%s] = %zd\n", str2, strnlen_s(str2, 110)); // intrinsic form bug
printf("len[%s] = %zd\n", str2, strlen(str2));
return 0;
}
"Pelles C for Windows, version 10.00" win7
CCFLAGS = -Tx64-coff -Ot -W1 -std:C17 -Zi#
Output:
len[1234] = 220
len[1234] = 4
When compile with 64bit and /Ot
size_t strnlen_s(const char *string, size_t max);
if length of string < max, strnlen_s return 2*max.
strnlen_s generated as inline code:
printf("len[%s] = %zd\n", str2, strnlen_s(str2, 110)); // intrinsic form bug
[000000014000101E] 488D7C2422 lea rdi,[rsp+22]
[0000000140001023] B96E000000 mov ecx,6E
[0000000140001028] 31C0 xor eax,eax
[000000014000102A] 4885FF test rdi,rdi
[000000014000102D] 7410 je 000000014000103F
[000000014000102F] 4989CA mov r10,rcx
[0000000140001032] F2AE repne scasb
[0000000140001034] 4C89D0 mov rax,r10
[0000000140001037] 7506 jne 000000014000103F
[0000000140001039] 48F7D1 not rcx
[000000014000103C] 4801C0 add rax,rax #wrong here? may be add rax,rcx?
[000000014000103F] 4989C0 mov r8,rax
[0000000140001042] 488D0DC7940000 lea rcx,[000000014000A510]
[0000000140001049] 488D542422 lea rdx,[rsp+22]
[000000014000104E] E87D000000 call 00000001400010D0
From Help file:
Intrinsic functions are generated as inline code. The C runtime functions in the first table are all enabled when optimizing for speed (/Ot option), and some when optimizing for size (/Os option). Individual functions can always be enabled through #pragma intrinsic and disabled through #pragma function.
The following C runtime functions have an intrinsic form:
Name X86 X64
......
strnlen_s no yes
......
