Strange compilation issue with gcc

Question

Why does the following program compile with , ... 编译，...

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

void foo(double x) {
   printf("%f", sin(2));
}

int main() {
   foo(1);
}

... while this other program doesn't?

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

void foo(double x) {
   printf("%f", sin(x));
}

int main() {
   foo(1);
}

It gives the following error message:

/tmp/ccVT7jlb.o: nella funzione "foo":
fun.c:(.text+0x1b): riferimento non definito a "sin"
collect2: error: ld returned 1 exit status*

Answer 1

You need to link to libm.so like this

gcc -Wall -Wextra -Werror source.c -o executable -lm

see the -lm