[gcc] 警告を一部分で抑止する

コンパイル警告(warning)を一部分で抑止する

警告が発生するソースコード

#include <stdio.h>
#include <stdlib.h>

int main(void) {
  int x = 1, y;
  y = (x++)*(x++);
  printf("x = %d, y = %d\n", x, y);
  return (EXIT_SUCCESS);
}

#include <stdio.h>

#include <stdlib.h>

int main(void) {

int x = 1, y;

y = (x++)*(x++);

printf("x = %d, y = %d\n", x, y);

return (EXIT_SUCCESS);

}

警告の例

$ gcc -Wall main.c
main.c: In function ‘main’:
main.c:6:9: warning: operation on ‘x’ may be undefined [-Wsequence-point]
   y = (x++)+(x++);
         ^

$ gcc -Wall main.c

main.c: In function ‘main’:

main.c:6:9: warning: operation on ‘x’ may be undefined [-Wsequence-point]

y = (x++)+(x++);

pragma命令で警告を抑止した例

#include <stdio.h>
#include <stdlib.h>

int main(void) {
  int x = 1, y;
#pragma GCC diagnostic ignored "-Wsequence-point"
  y = (x++)*(x++);
#pragma GCC diagnostic warning "-Wsequence-point"
  printf("x = %d, y = %d\n", x, y);
  return (EXIT_SUCCESS);
}