[CMake] cmake integration

[Brandon J. Van Every]

Pavel Volkovitskiy wrote:
>
>
> It's not my CMakeList.txt, i use sim-im as example of program with 
> cmake based buildsystem
> CMakeList.txt (from sim-im sources) always checks for ASPELL but 
> doesn't uses it if USE_KDE=TRUE
>
> I want to know if this common practice (find everything even if you 
> don't need it) or if this CMakeList.txt has bugs
> (ie it shouldn't check for aspell if it's not going to be used)

CMake doesn't search for anything unless the programmer says so.  So 
it's not like Automake in that regard; you're never going to be looking 
for hordes of useless stuff, unless the programmer actually wanted to do 
that.  When the programmer wants to find something, the following 
paradigm is common:

FIND_LIBRARY(LIBRARY_PATH ...)
IF(LIBRARY_PATH)
  blah
ELSE(LIBRARY_PATH)
  blah
ENDIF(LIBRARY_PATH)

That is, the find is performed unconditionally, and the results are used 
conditionally.  This isn't a bug, it's just a style.  The call is 
FIND_LIBRARY, not REQUIRE_LIBRARY.  Nothing has been promised about how 
the results will be used.

There's nothing stopping anyone from writing code like

IF(KDE)
  FIND_LIBRARY(ASPELL_PATH ...)
  blah
ELSE(KDE)
  blah
ENDIF(KDE)

but nobody's going to do that without a motive.  It sounds like the real 
problem here is that conary is improperly designed.

>
> Now about buildrequrements auto-discover.
> after conary build binary package with configure script it looks in 
> config.log to discover build requrements of package
> (ie if configure scripts checks for libaspell.so -> aspell should be 
> added as build requirements for this package)
>
> with cmake based build system i guess CMakeCache.txt is equivalent for 
> config.log
> so now conary builds package
> (ie cmake; make; make install)
> and then looks in CMakeCache.txt and if it found 
> "ASPELL_LIBRARIES:FILEPATH=/usr/lib64/libaspell.so"
> it adds aspell as build requirement for package

Why dos conary assume that a mere path is a build requirement?  That's a 
bad assumption / a hack.


>
> the problem is that sim-im always tries to find aspell library even if 
> it will not use it during build
>
> so i wonder if there is better way exist to auto-discover real build 
> requirements of package

That I don't know.  I haven't RTFM on that issue, or needed it for my 
own work.  I defer to others on this point.  A reliable mechanism would 
indeed be the basis for a correct conary design.


Cheers,
Brandon Van Every