Making writing Config.cmake files easier - updated example

[Yury G. Kudryashov]

Alexander Neundorf wrote:

> On Monday 16 January 2012, Yury G. Kudryashov wrote:
>> Alexander Neundorf wrote:
>> > On Sunday 15 January 2012, Yury G. Kudryashov wrote:
>> >> 15 January 2012 20:06:51 Alexander Neundorf written:
>> >> The only comment: there are 4 possible combinations of
>> >> cmake -DLIB_INSTALL_DIR=relative_or_absolute -
>> >> DINCLUDE_INSTALL_DIR=relative_or_absolute
>> >> It seems that your library will not be relocatable if
>> >> INCLUDE_INSTALL_DIR is set to an absolute path.
>> > 
>> > I think I can improve this a bit more, but yes, this may be a
>> > limitation, but IMO an acceptable limitation.
>> > If you want to create a relocatable package, don't set absolute paths.
>> > (I know all install dirs are absolute with kdelibs4, this will change
>> > with KDE frameworks).
>> 
>> This can be solved if you store the original prefix in Config.cmake.
>> 
>> >> Basically, my goal is a macro that writes and installs *Config.cmake
>> >> files in "simple" cases and makes library available to find_package()
>> >> both from another subdirectory of the same project and after
>> >> installation. What do you think about this approach?
>> > 
>> > Looks quite good.
>> > We must make sure that it doesn't keep developers from adding custom
>> > stuff to the Config.cmake files. But this looks quite good with your
>> > "EXTRA_VARS" and "EXTRA_CONFIG_FILE" options.
>> > 
>> > I think it may need a special option for specifying variables and
>> > values which are directories (and so which have to be made
>> > absolute/relocated).
>> 
>> Yes. I have a code for this but it needs a good syntax for both
>> "internal" and "installed" version of Config.cmake.
>> 
>> >> Actually, I'd prefer to have
>> >> install(EXPORT ... ... INSTALL_CONFIG [bool] PACKAGE_NAME
>> >> [=ExportName])
>> > 
>> > I see. Still, exactly the same is possible using install(FILES ...), so
>> > I see the chances for getting this accepted into cmake as uncertain.
>> > 
>> > Oh, wait.
>> > install_cmake_config_files() creates *and* installs the files ?
>> 
>> install(EXPORT ...) generates Export file *and* installs it. So,
>> install(CONFIG_FOR_EXPORT ...)
>> can do the same. Actually, the file can be generated at 'make install'
>> time.
> 
> Ok. Still I'd prefer something similar to
> write_basic_config_version_file(), which creates a FooConfigVersion.cmake
> which is then installed using install(FILES).
> 
> If somebody has that code already, add
> write_basic_config_file()
> and putting the resulting file in the same install(FILES ) call seems like
> a straightforward extension.
I have to know the DESTINATION at generation time to hardcode correct 
relative paths.
-- 
Yury G. Kudryashov,
mailto: urkud at mccme.ru