Re: make install : config.h?

[Guido Draheim]

Am 24.07.2013 11:39, schrieb LRN:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 24.07.2013 11:53, Daniel Pocock wrote:
> > I've come across a project that is installing config.h when "make
> > install" is invoked
> >
> > The project in question is the SRTP library.  Some of the headers are
> > actually dependent on some config.h stuff, for example:
> >
> > https://github.com/cisco/libsrtp/blob/master/crypto/include/integers.h
> >
> > has a lot of conditional logic
> >
> > The result of including that extra copy of config.h is that when I build
> > other projects, the compiler has two copies of config.h available and
> > complains about the redefinition of things like PACKAGE_NAME.  It's
> > quite possible that there are less obvious side-effects as well.
> >
> > Can anybody comment on the right way to do this?  Should integers.h
> > (above) be changed?  Or should other projects using libsrtp find ways to
> > work around this?
> This is wrong. No one should ever install a header named 'config.h'.
>
> If a project must install its config.h, it should install a renamed copy
> of it (or rename it altogether and use it under the new name even
> internally; 'config' part of 'config.h' is not mandatory, it's just the
> usual name).

A "config.h" should not even get installed in a renamed fashion - if two
libraries have these then you will see errors coming up speaking of
"duplicate defintion"s. You will even get subtle differences in library
behaviour when the precompiler definitions in the two installed config.h have a
different value due to a different configure.ac content. I've even seen errors
when a function is defined conditionally on an environment check.

So an explicit pkgconfig.h should try to use some kind of prefix for the
definitions so that you would not try to depend a precompiler-if on the config
value of another project. To make it easier I had written a macro for it that
will take the config.h creating a pkgconfig.h by adding the library name as
a proper prefix, see:

http://www.gnu.org/software/autoconf-archive/ax_prefix_config_h.html

> Or even better, separate config.h into two files - use one internally
> (normal config.h), while the other will be both installed and used
> internally (sadly, i can't tell you how exactly that can be done;
> config.h.in is generated by autoheader, so they will have to either
> tinker with autoheader, or just form the second (smaller) header
> manually, at least an .in template of it).
>
> - --
> O< ascii ribbon - stop html email! - www.asciiribbon.org
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.11 (MingW32)
>
> iQEcBAEBAgAGBQJR76C3AAoJEOs4Jb6SI2CwbfcIAM4p8Og/fQLLc39nkS5GClFa
> j0mJuZOlnFql/Al9oLSZ1O+imfuxqgJ1rmS4InlHmTMMxeWRzvbH2REwMXkIL+Rh
> tnE+AgU3JcXjMAYKg/OrGmNZUn8cLosDqe/R149uHgSVRZyKdaygdVoW3q4dc1JI
> 0Wkhjhp7Rz7qgYhgxBUOnvB7WW4Lb5E3JtWdPuWaWShnA8BeIbKRlnSmqTwLUZ5y
> MkN+7umbaqBHUMeSO9Xw2kr0F5Tc85ALw8K7mkOCIvGI4e8GxbcVVxAlR8KshTO5
> uVuWpeunoFxivhN17AFW3JNDf6xKBCJrdPthJv/qdo5jCwM7NgWN3YbeRM0N/w0=
> =d7+f
> -----END PGP SIGNATURE-----
>
> _______________________________________________
> Autoconf mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/autoconf