c++ - sscanf 中 uint16_t 的正确且可移植的 (Clang/GCC) 修饰符是什么？

Question

当我尝试编译这段代码时收到一条警告消息sscanf(value, "%h"PRIu16 "B", &packet_size) 使用 Clang 600.0.57 (OS X)。

warning: format specifies type 'unsigned char *' but the argument has type 'uint16_t *'
      (aka 'unsigned short *') [-Wformat]
    if (sscanf(value, "%h" PRIu16 "B", &packet_size) == 1) {
                       ~~~~            ^~~~~~~~~~~~

但是如果我删除修饰符“h”，那么我会在 GCC 4.8.3 (Scientific Linux 7) 中收到以下错误。

warning: format ‘%u’ expects argument of type ‘unsigned int*’, but argument 3 has type ‘uint16_t* {aka short unsigned int*}’ [-Wformat=]
     if (sscanf(value, "%" PRIu16 "B", &packet_size) == 1) {

                                                   ^

sscanf 中 uint16_t* 的正确且可移植的修饰符是什么？

=== 在下面添加了更多不言自明的示例 ===

测试.c

#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS 1
#endif
#include <inttypes.h>
#include <stdio.h>

int main() {
  char* str = "16 bits";
  uint16_t u16;
  sscanf(str, "%h" PRIu16 " bits", &u16); // Clang warning
  sscanf(str, "%" PRIu16 " bits", &u16); // GCC warning
  sscanf(str, "%" SCNu16 " bits", &u16); // OK for both compilers

  printf("%" PRIu16 " bits\n", u16);

  return 0;
}

Clang 警告

$ clang test.c -Wall -Wextra
test.c:10:36: warning: format specifies type 'unsigned char *' but the argument
      has type 'uint16_t *' (aka 'unsigned short *') [-Wformat]
  sscanf(str, "%h" PRIu16 " bits", &u16); // Clang warning
               ~~~~                ^~~~
1 warning generated.

海湾合作委员会警告

$ gcc -Wall -Wextra test.c
test.c: In function ‘main’:
test.c:11:3: warning: format ‘%u’ expects argument of type ‘unsigned int *’, but argument 3 has type ‘uint16_t *’ [-Wformat=]
   sscanf(str, "%" PRIu16 " bits", &u16); // GCC warning
   ^

Answer 1

正如@EOF 在他们的评论中所说，fscanf和 fprintf每个都有自己的宏。

在final C99 draft , §7.8.1 第 4 条和第 5 条(第 199 页)说 <inttypes.h>应定义以下宏:

4. The fscanf macros for signed integers are:

   SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
   SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR

5. The fscanf macros for unsigned integers are:

   SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
   SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
   SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR

如果你想阅读uint16_t作为十进制数 fscanf , 你必须使用 SCNu16 .

例子:

#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>

int main(void) {
    uint16_t input;

    int items = scanf("fetch %" SCNu16 " bits", &input);

    if (items == 1) {
        printf("I'm busy, go fetch those %" PRIu16 " bits yourself.\n", input);
    } else {
        printf("I don't understand what you're saying.\n")
    }

    return 0;
}