Including files in C

问题

I want to make a simple function involving sqrt(), floor() and pow(). So, I included <math.h>. When I try to use my function, my program says that sqrt() and floor() do not exist. I've triple checked my files and rewritten them, but it still gives the same error. Just to check if there was anything wrong with the <math.h> directory, I made another separate file that calculated the same thing and it worked. I am clueless right now. What am I doing wrong?

The code of the non functioning program:

#include <math.h>
#include "sumofsquares.h"

int sumofsquares(int x){
   int counter = 0;
   int temp = x;

   while(temp != 0){
      temp = temp - (int)pow(floor(sqrt(temp)), 2);
      counter ++;
   }
    return counter;
}

The working test file:

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

int main(void){
   printf("%d", (int)pow(floor(sqrt(3)), 2));
}

the error is this

/tmp/ccm0CMTL.o: In function sumofsquares': /home/cs136/cs136Assignments/a04/sumofsquares.c:9: undefined reference to sqrt' /home/cs136/cs136Assignments/a04/sumofsquares.c:9: undefined reference to floor' collect2: ld returned 1 exit status`

I am using runC on a virtual Ubuntu OS to compile

回答1:

You're probably missing the -lm argument to gcc, required to link the math library. Try:

gcc ... <stuff> ... -lm

There are at least two C FAQs relevant to your problem:

• 14.3
• 13.26

来源：https://stackoverflow.com/questions/9399480/including-files-in-c