[linux-help] Re: A c problem

[Steven Saner <ssaner@xxxxxxxxxxxxxxx>]

You need to add -lm to the command line. That will tell gcc to link to
the math library.

Steve


On Mon, Aug 05, 2002 at 03:28:30PM -0500, bruce wrote:
> 
> I'm in chapter 2 of Kernighan and Richey, trying to learn c programming.
> I have been using gcc to compile my programs.  I wrote a very simple program 
> using math.hand sqrt:
> 
> #include <stdio.h>
> #include <math.h>
> main()                   {
> double m, n=8.0;
> m=sqrt(n);
> printf("%f\n",m);
> return 0;
> }
> 
> and tried to compile it with "gcc -o test-p45 test-p45.c"
> 
> It errored with 
>  undefined reference to `sqrt'
> 
> Same thing when I used kgcc and gcc3.
> I compiled it with g++ and it compiled and ran correctly.
> 
> Can anyone tell me why gcc seems to not be linking to math.h?
> Or should I be using g++ ? (I thought g++ was for C++ and gcc was for plain 
> old c.
> 
> I am using RH 7.2. and KDE.
> bruce
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