Re: How to test if a autoconf macro exists?

[Stepan Kasal]

Hello,
 [this would better fit to address@hidden, but the difference is
not always easy to understand]

On Mon, Feb 04, 2008 at 11:35:59AM +0100, Santiago Capel Torres wrote:
> So, it looks like I can not use AM_PATH_XML2 before installing 
> libxml2-devel, so I can not test if it is installed :(

you are confusing two roles here:

- the user who gets the tarball of your project should be ablo to
  install it easily by "configure, make, make install"

In this case the configure script, which is part of the tarball, is
flexible enough to detect if libxml2 is installed, and many other
aspects of the system which is going to be used for the build.

- Developpers, who get the minimal set of the primary sources from
  the CVS, need full range of developper tools to be able to build
  from the minimal tree, and to build the tarball for others
  (make dist)

Those people are supposed to be able to install libxml2-devel, or the
needed .m4 file alone, to satisfy the requirements of the autotools.
Moreover, you are probably writing a "bootstrap script" for them, so
you can check the tools for known errors and add hints for them.

For people who are only supposed to test the latest snapshot, it is
always safer to provide a daily snapshot tarball, generated by "make
dist" on an up-to-date comp.

[Back to your question: yes, you can do something like
  m4_ifdef([AM_PATH_XML2], [AM_PATH_XML2([....])])
But this solution would confuse aclocal and the macro AM_PATH_XML2
would not get to aclocal.m4 even if it is available.  So please do
not use m4_ifdef in this case.]

Hope this clarifies the situation,
        Stepan Kasal