Re: Checking lib requires include

[Ralf Wildenhues]

Hi Paulo,

* Paulo Jorge Matos wrote on Thu, Nov 10, 2005 at 06:42:00PM CET:
> On 10/11/05, Paulo Jorge Matos <address@hidden> wrote:
> >
> > The problem is I'm checking for a library using AC_CHECK_LIB and I was
> > expecting to be able to say: (glpk - gnu linear programming kit)
> > AC_CHECK_LIB(glpk)
> > and that's it. However, I need to also give a function name. Why?

Some linkers do not error out if the named library was not found but
also not used to satisfy a certain symbol.  (At least I believe so.)

> > I imagine this is the only way to check if the library is linkable...
> > so, I asked for lpx_create_prob. (does this function need any
> > particular feature?)
> > Still config.log says it does not work because the test program needs
> > to include glpk.h.

I don't think this is the exact error it gives.  
If lpx_create_prob is a function in libglpk, that should work.
It may be that they used a macro to define it in some header file.
Then use a different function that is not implemented as a macro.

But the error you are citing from comes most likely from a different
test.  It is usually better to quote (copy and paste from config.log)
error messages, so possible misunderstandings are avoided.

> > How can I tell that to autoconf?
>
> Oh well, this is a quite nice trick.
> Checking for main, i.e.
> AC_CHECK_LIB(glpk, main)

This is not a trick.  This is plain broken.

There is no need for Autoconf if you are going to disable its primary
use anyway.  Might as well just set
  LIBS="-lglpk $LIBS"
right away instead of invoking AC_CHECK_LIB.

Cheers,
Ralf