I'm very new to C and I have this code:
#include <stdio.h>
#include <math.h>
int main(void)
{
double x = 0.5;
double result = sqrt(x);
printf("The square root of %lf is %lf\n", x, result);
return 0;
}
But when I compile this with:
gcc test.c -o test
I get an error like this:
/tmp/cc58XvyX.o: In function `main':
test.c:(.text+0x2f): undefined reference to `sqrt'
collect2: ld returned 1 exit status
Why does this happen? Is sqrt() not in the math.h header file? I get the same error with cosh and other trigonometric functions. Why?
ベストアンサー1
The math library must be linked in when building the executable. How to do this varies by environment, but in Linux/Unix, just add -lm to the command:
gcc test.c -o test -lm
The math library is named libm.so, and the -l command option assumes a lib prefix and .a or .so suffix.