Re: undefined sqrt()

["Theo. Sean Schulze" <tschulze@teamfinders.org>]

Glynn,

Thanks for the explanation.  I understand now.  After getting your explanation, I did a bit of web browsing to try to find a page that tells me what libraries I need for which header files, but I haven't been too successful.  Do you know of a URL where I could find that info?

Thanks,
Sean

On Fri, Oct 25, 2002 at 09:17:07AM +0100, Glynn Clements hunted and pecked out:
> 
> Theo. Sean Schulze wrote:
> 
> > Thanks. The "-lm" did it. Why? I see from the gcc man page that the
> > "-l" is a linker option. Am I right that the linker then searches for
> > "libm.a"?
> 
> To be precise, it will normally look for libm.so (shared library)
> first (unless the -static switch was used), then look for libm.a.
> 
> > Again, why, if I am right, would it need to after I included
> > math.h? Isn't sqrt() in math.h?
> 
> The declaration is in math.h, but a declaration simply tells the
> compiler that the function exists, along with the number and types of
> its arguments and its return type.
> 
> In order to produce a working program, you have to provide the actual
> code which implements that function. In the case of sqrt(), the code
> is in libm.
> 
> For functions which are in libc, you don't have to provide any -l
> switches, as gcc (when used for linking) automatically instructs the
> compiler to link against libc.
> 
> -- 
> Glynn Clements <glynn.clements@virgin.net>

-- 
Theo. Sean Schulze
tschulze@teamfinders.org