headers installation and compilation tests

[David Faure]

> On Monday 29 November 2010, David Faure wrote:
> > On Monday 09 August 2010, Volker Krause wrote:
> > > It also has a test that makes sure all headers compile with strict
> > > flags (QT_NO_CAST_FROM_ASCII, etc), might be interesting for kdelibs as
> > > well.
> > 
> > Yep, very interesting, I just wrote the attached patch in order to check
> > this in kdelibs - without using the forwarding headers though, since they
> > don't compile in kdelibs before being installed.
> > Instead I'm doing this per-library, using its already set up include
> > directories and their list of installed headers. Attaching, for review on
> > kde- buildsystem. Tested on kdeui and kio, works fine, needs to be
> > applied to all other libs as well.

On Sunday 05 December 2010, Alexander Neundorf wrote:
> MacroHeaderCompilationTest.cmake:
> * it doesn't have docs at the top

Sure, was waiting for input first. Added now.

> * does it have to use kde4_add_executable() ? This adds mainly automoc, and
> some RPATH settings. I think add_executable() should work too.

Fixed.

> * the name is too generic, since it tests something very special (can
> header files be compiled if certain Qt macros are set)

Well it also tests that the headers actually compile. Think of pure interfaces 
for instance: nothing in kdelibs compiles them, so a syntax error wouldn't be 
detected while compiling kdelibs; this test would detect it.
This is really "test compiling these headers", so 
macro_header_compilation_test doesn't seem that far off to me. Any better 
suggestion, otherwise?

> * should this macro be installed ?

Volker replied yes, so I added it now.

> * why is the header_compile.cpp not rewritten everytime ?

To speed things up.

> Hmm, I guess the test is rebuilt everytime cmake runs, right ?
> file(WRITE/APPEND ...) directly write the file, so its date changes.

Yes.

> If you use configure_file(), it changes the target file only if its
> contents differ from the source file. So you could use the file() commands
> to generate the file, and then basically copy that file using
> configure_file(), so it will only have changed (and then be rebuilt) when
> the contents actually changed.

Sounds complicated, compared to the next solution (well, I guess?)

> Or, the test could consist of actually creating a tiny cmake project, which
> then builds the executable. I.e. header_compile.cpp would not be build at
> build time of kdelibs, but at "make test" time of kdelibs.
> This is done a lot in the tests for cmake itself.

Sounds good but I have no idea how to do that. Can you do it, or tell me how 
with more details?

-- 
David Faure, faure at kde.org, http://www.davidfaure.fr
Sponsored by Nokia to work on KDE, incl. Konqueror (http://www.konqueror.org).