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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: Need help with an odd error...
Date: Sun, 24 May 2015 15:38:46 -0700
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"Chris M. Thomasson" <cristom@charter.net> writes:
[...]
> #include <math.h>
> #include <stdio.h>
>
> double
> my_cos(double v)
> {
>    return cos(v);
> }
>
> int main()
> {
>    printf("my_cos(3.14) = %f\r\n", my_cos(3.14));
>
>    return 0;
> }
[...]
> sh-4.3# gcc -o main *.c
>
> /tmp/ccXNUoFK.o: In function `my_cos':
>
> main.c:(.text+0x1b): undefined reference to `cos'

Compile with:

    gcc -o main *.c -lm

(Prepare for a flame war over whether the need to specify "-lm" when
using the math library is a bug or not.)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"