那我在下面的程序丢失？ [英] What am I missing in the following program?

问题描述

#include<stdio.h>    
#define TOTAL_ELEMENTS (sizeof(array) / sizeof(array[0]))
int array[] = {23, 34, 12, 17, 204, 99, 16};

int main() {
    int d;

    for (d = -1; d <= (TOTAL_ELEMENTS - 2); d++)
        printf("%d\n", array[d + 1]);

    return 0;
}

为什么for循环一次也没有跑？

Why is the for loop not run even once?

推荐答案

的问题是，的sizeof（）收益为size_t 这是无符号的。 的比较-1 与 TOTAL_ELEMENTS - 2 应导致表示你的警告已经比较无符号有符号。当这种情况发生的比较中， 1 被转换为无符号值，该值 MAX_UINT 。在32位平台上，无论是 1 和 MAX_UINT 是 0xFFFFFFFF的。

The issue is that sizeof() returns size_t which is unsigned. Comparison of -1 with TOTAL_ELEMENTS - 2 should result in a warning indicating you have compared unsigned with signed. When this comparison happens, the -1 is converted to an unsigned value which is MAX_UINT. On a 32-bit platform, both -1 and MAX_UINT are 0xFFFFFFFF.

您 TOTAL_ELEMENTS（）宏可以纳入强制转换为（INT）但是这不是技术上是正确的，因为为size_t 有一个较大的值范围比 INT 。最好改变你的循环变量，使其声明为为size_t 而不是变成负的。

Your TOTAL_ELEMENTS() macro could incorporate a cast to (int) but that isn't technically correct because size_t has a larger value range than int. Best to change your loop variable so that it is declare as size_t and never becomes negative.

这篇关于那我在下面的程序丢失？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！