GCC沒有抱怨數組越界

Question

當然，這項權利有問題嗎？

#include <stdio.h>

#define NUM 1
#define NUM_SWARMS 3

typedef float coor_t[NUM];
typedef coor_t gBestX_t[NUM_SWARMS];

gBestX_t gBestX;

int main()
{
  gBestX[0][1] = 3.0;
  gBestX[1][1] = 3.0;
  gBestX[8][1] = 4.0;

  printf("%f\n", gBestX[8][1]);

  return 0;
}

在我看來，這是將gBestX創建為大小為[1] [3]的2D數組，但是gcc或valgrind對此有所抱怨，並且我得到了正確的輸出（4.0）。 這不是對數組的違反嗎？

Answer 1

如果啟用該警告，gcc僅會警告界限。 有關更多詳細信息，請參見gcc手冊頁：

   -Warray-bounds
   -Warray-bounds=n
       This option is only active when -ftree-vrp is active (default for -O2 and above). It warns about
       subscripts to arrays that are always out of bounds. This warning is enabled by -Wall.

       -Warray-bounds=1
           This is the warning level of -Warray-bounds and is enabled by -Wall; higher levels are not, and must
           be explicitly requested.

       -Warray-bounds=2
           This warning level also warns about out of bounds access for arrays at the end of a struct and for
           arrays accessed through pointers. This warning level may give a larger number of false positives and
           is deactivated by default.

Answer 2

您需要更新的gcc。 編譯時收到警告：

Bruces-MacBook-Pro：test bruce $ gcc -o t15 t15.c t15.c：13：4：警告：數組索引1超出了數組的末尾（包含1個元素）[-Warray-bounds] gBestX [ 0] [1] = 3.0; ^〜t15.c：9：1：注意：此處聲明的數組'gBestX'gBestX_t gBestX; ^ t15.c：14：6：警告：數組索引1超出了數組的末尾（包含1個元素）[-Warray-bounds] gBestX [1] [1] = 3.0; ^〜t15.c：9：1：注意：此處聲明的數組'gBestX'gBestX_t gBestX; ^ t15.c：15：8：警告：數組索引1超出了數組的末尾（包含1個元素）[-Warray-bounds] gBestX [8] [1] = 4.0; ^〜t15.c：9：1：注意：此處聲明的數組'gBestX'gBestX_t gBestX; ^ t15.c：17：25：警告：數組索引1超出了數組的末尾（包含1個元素）[-Warray-bounds] printf（“％f \\ n”，gBestX [8] [1]） ; ^〜t15.c：9：1：注意：此處聲明的數組'gBestX'gBestX_t gBestX; ^產生4條警告。