Question

我的代码中有以下功能：

int numberOverflow(int bit_count, int num, int twos) {
    int min, max;
    if (twos) {
        min = (int) -pow(2, bit_count - 1);        \\ line 145
        max = (int) pow(2, bit_count - 1) - 1;
    } else {
        min = 0;
        max = (int) pow(2, bit_count) - 1;         \\ line 149
    }
    if (num > max && num < min) {
        printf("The number %d is too large for it's destination (%d-bit)\n", num, bit_count);
        return 1;
    } else {
        return 0;
    }
}

在编译时，我收到以下警告：

assemble.c: In function ‘numberOverflow’:
assemble.c:145: warning: incompatible implicit declaration of built-in function ‘pow’
assemble.c:149: warning: incompatible implicit declaration of built-in function ‘pow’

我对导致这种情况的原因感到茫然......有什么想法吗？

Answer 1

您需要加入math.h

why exactly do we get this warning?

Answer 2

根据警告的措辞，您似乎正在使用gcc？也许值得尝试另一个编译器，即clang。这个告诉我：

 test-pow.c:15:18: warning: implicitly declaring C library function 'pow' with type 'double (double, double)' [-pedantic]
 test-pow.c:15:18: note: please include the header <math.h> or explicitly provide a declaration for 'pow'

从C数学库的pow功能获得警告

2 个答案: