c - 如何使用 -D 选项将参数中的字符串化宏传递给 gcc

Question

我正在使用以下命令编译以下代码:
gcc test.c -D HEX=0xFFFF

#include <stdio.h>
#define NOERR 0
#define ERR 1

/*
 * Some Code 
 */
main()
{
    printf(#HEX);
}

我得到以下输出:

Ex2_03.c:33:9: error: stray ‘#’ in program
  printf(#HEX);
         ^
Ex2_03.c:33:2: warning: passing argument 1 of ‘printf’ makes pointer from integer without a cast [enabled by default]
  printf(#HEX);
  ^
In file included from Ex2_03.c:1:0:
/usr/include/stdio.h:362:12: note: expected ‘const char * __restrict__’ but argument is of type ‘int’
 extern int printf (const char *__restrict __format, ...);
            ^
Ex2_03.c:33:2: warning: format not a string literal and no format arguments [-Wformat-security]
  printf(#HEX);
  ^

Answer 1

你得到一个错误，因为 # 运算符只能在预处理器指令中使用。

您需要字符串化您的宏。字符串化需要一个两级宏:

#define STRINGIFY_(x)  #x
#define STRINGIFY(x)   STRINGIFY_(x)

printf(STRINGIFY(HEX));