Problem with header files.

Problem with header files.

[Matt R]

Dear GCC Gurus, 
I have a problem getting GCC to refer to header files.
For example the following program....
------------Code Begins Here------------
#include <stdio.h>
#include <math.h>


main() {
    float uno;
    float  duo;
    uno=7.778;
    duo=sqrt(uno);
    printf("sqrt of %f is %f \n", uno, duo);
}

------------Code Ends Here--------------
Produces the following message at compile time...

[fakeuser@fakehost BeginC]$ gcc trial.c
/tmp/ccBm2UFL.o: In function `main':
/tmp/ccBm2UFL.o(.text+0x1b): undefined reference to `sqrt'
collect2: ld returned 1 exit status */

__________________________________________

What is going on?  I would really appreciate your advice on this
one.  I have to admit to being a newbie to C programing.
I have installed glibc 2.2.12 (full install), and gcc 2.9.6-85, and 
am using RedHat 7.0 distro.  The original versions of glibc gave the 
same errors.

Looking forward to your advice...otherwise I will end up doin my
iminent assignments on DOS....a fate worse than death.

Matt Redding

Re: Problem with header files.

[David Berthelot]

Ok I think it's quite easy: you forgot to specify the library for
linking, you should do:

gcc trial.c -lm

libm is the math library, when referring to a library you put -l
(instead of lib),
so -lm link with the math library.

David

Matt R wrote:

> Dear GCC Gurus,
> I have a problem getting GCC to refer to header files.
> For example the following program....
> ------------Code Begins Here------------
> #include <stdio.h>
> #include <math.h>
>
> main() {
>     float uno;
>     float  duo;
>     uno=7.778;
>     duo=sqrt(uno);
>     printf("sqrt of %f is %f \n", uno, duo);
> }
>
> ------------Code Ends Here--------------
> Produces the following message at compile time...
>
> [fakeuser@fakehost BeginC]$ gcc trial.c
> /tmp/ccBm2UFL.o: In function `main':
> /tmp/ccBm2UFL.o(.text+0x1b): undefined reference to `sqrt'
> collect2: ld returned 1 exit status */
>
> __________________________________________
>
> What is going on?  I would really appreciate your advice on this
> one.  I have to admit to being a newbie to C programing.
> I have installed glibc 2.2.12 (full install), and gcc 2.9.6-85, and
> am using RedHat 7.0 distro.  The original versions of glibc gave the
> same errors.
>
> Looking forward to your advice...otherwise I will end up doin my
> iminent assignments on DOS....a fate worse than death.
>
> Matt Redding

Re: Problem with header files.

[Alexandre Oliva]

On Aug  3, 2001, Matt R <nimrod99@dingoblue.net> wrote:

> I have a problem getting GCC to refer to header files.

No, your problem is not about header files, it's about libraries, that
are a completely different thing.  Headers supply declarations or
inline implementations; libraries supply implementations for functions
that are only declared in headers, or that fail to be inlined.  The
library in which sqrt() is defined is the math library, that you can
link in by adding `-lm' to the link command.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me

Re: Problem with header files. YeHaaaaaa!!!!!

[Matt R]

Thankyou  very much.

Thanks to you the pain is over.
Great to see you are still able to put up with
newbie questions...as dumb as his one.

If you have got
a question about soil contamination
or soils in general, I'd be glad to try to answer you.
But I am very much a begginer with c and gcc.

Thanks, 

Matt Redding