Issues with log() call

Question

Why won't this program run?

#include<stdio.h>
int main()
{
    printf("%f\n", log(36.0));
    return 0;
}

You had better to `#include `. The prototype of log is `double log(double arg);` and, as you have not included it, the compiler is assuming it returns an `int` value. — Luis Colorado, Mar 13 '15 at 07:56

score 4 · Accepted Answer · answered Mar 11 '15 at 04:57

4

You have to include

#include<math.h>

This is because math.h is a header file in the standard library of C programming language designed for basic mathematical operations.

answered Mar 11 '15 at 04:57

3

And link the math library with `-lm` as a compiler option. – squiguy Mar 11 '15 at 05:03
2

@squiguy actually in this case both `gcc` and `clang` can [use builtin functions if the argument is a constant expression in many cases](http://stackoverflow.com/a/24294632/1708801) but in the general case you need to use `-lm`. – Shafik Yaghmour Mar 11 '15 at 13:09

1 Answers1