对“pow"和“floor"的未定义引用 [英] Undefined reference to `pow' and `floor'

问题描述

我正在尝试用 C 制作一个简单的斐波那契计算器，但是在编译 gcc 时告诉我我缺少 pow 和 floor 函数.怎么了?

I'm trying to make a simple fibonacci calculator in C but when compiling gcc tells me that I'm missing the pow and floor functions. What's wrong?

代码:

#include <stdio.h>
#include <math.h>

int fibo(int n);

int main() {
        printf("Fib(4) = %d", fibo(4));
        return 0;
}

int fibo(int n) {
        double phi = 1.61803399;

        return (int)(floor((float)(pow(phi, n) / sqrt(5)) + .5f));
}

输出:

gab@testvm:~/work/c/fibo$ gcc fib.c -o fibo
/tmp/ccNSjm4q.o: In function `fibo':
fib.c:(.text+0x4a): undefined reference to `pow'
fib.c:(.text+0x68): undefined reference to `floor'
collect2: ld returned 1 exit status

推荐答案

你需要用链接标志-lm编译，像这样:

You need to compile with the link flag -lm, like this:

gcc fib.c -lm -o fibo

这将告诉 gcc 将您的代码链接到数学库.请务必将标志放在要链接的对象之后.

This will tell gcc to link your code against the math lib. Just be sure to put the flag after the objects you want to link.

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