sscanf 中 uint16_t 的正确便携 (Clang/GCC) 修饰符是什么？

Question

我在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* 的正确便携修饰符是什么？

=== 在下面添加了更多不言自明的示例 ===

test.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;
}

叮当警告

$ 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.

GCC 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 中，§7.8.1 第 4 条和第 5 条（第 199 页）指出 <inttypes.h> 应定义以下宏：

The fscanf macros for signed integers are:

SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR

The fscanf macros for unsigned integers are:

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

如果要用 fscanf 将 uint16_t 读作十进制数，则必须使用 SCNu16.

示例：

#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;
}

sscanf 中 uint16_t 的正确便携 (Clang/GCC) 修饰符是什么？

What is the correct and portable (Clang/GCC) modifier for uint16_t in sscanf?

c

c++

gcc

clang