🚀 go-pugleaf

Hi!

lanx@siu.EDU wrote:
>I installed gcc together with Linux from the Linux Slackware package. The
>bin, include and lib directories are directly under /usr, which is different
>from what you described for a separate installation in which they should be
>under /usr/local. Anyway, gcc generally works except it can not find the
>intrinsic functions (like sin, sqrt, etc.) that need <math.h>. My test
>program is like this:
>
>#include <stdio.h>
>#include <math.h>
>main()
>{
> double x;
> x=sin(3.14159/6.0);
> printf("x=%f\n",x);
>}
>
>when I used gcc to compile and link the program, it gave me an error message:
>/tmp/xxxxxxxx:   undefined reference to 'sin'
>I checked /usr/include directory, both stdio.h and math.h are there! Do you
>know what the problem is? Please help me.
>Jian
>

Have you tried to use the -lm option? If not, do it, ... If that was your
problem look in /usr/faq/faq where you'll find many faqs about gcc (it is 
necessary to install the F series, of course)

In brief, it is necessary to use -l option when you want to use any library
in /usr/include, like, for instance, libm.a, the mathematical library. When 
you want to use such a library you must include -lxxx, where xxx is the name of
the library, without the initial letters 'lib' and without the last ones '.a',
so, for 'libm.a' you'll need '-lm'. Notice that -l option must be put the last
one, so, for compiling your prog, you ought to do something like:

% gcc proof.c -o proof -lm

if your prog was called proof.c

I hope this helps

Carlos Linares Lopez
Artificial Intelligence Laboratory
Computer Science Faculty
Polithecnic University of Madrid
Spain