[CMake] FindBoost.cmake from 2.6

[Fernando Cacciola]

Hi Andreas Pakulat,

I'm in charge of the CMake build installation for CGAL (www.cgal.org) and I 
so far had been using my own FindBoost module hoping to get rid of it as 
soon as the official module got improved.

While the latest FindBoost is a significant improvement over the previous 
version, there are still a few issues with it:

(1)
It should use $ENV{ProgramFiles} instead of "C:\Program Files"

(2)
If you google for both "BOOSTROOT" and "BOOST_ROOT" you'll find that both 
enviroment variables are equally used among the large boost users community, 
thus I would suggest to use both in the module. In particular, CGAL had long 
been using BOOSTROOT, and I'd hate to tell our users to rename that.

(3)
The following logic:

    IF( WIN32 )
      SET(_boost_INCLUDE_SEARCH_DIRS ${BOOST_ROOT} 
${_boost_INCLUDE_SEARCH_DIRS})
    ELSE( WIN32 )
      SET(_boost_INCLUDE_SEARCH_DIRS ${BOOST_ROOT}/include 
${_boost_INCLUDE_SEARCH_DIRS})
    ENDIF( WIN32 )

is indeed correct and needed since on windows the root folder is itself the 
include folder.

However, this logic is used for the case of the CMake variable BOOST_ROOT, 
but not for the enviroment variable BOOST_ROOT
(this in fact causes the search to fail in my machine when I arrange it to 
depend solely on the enviroment variable BOOST_ROOT)

I suggest to unify the code by doing:

if ( NOT BOOST_ROOT AND NOT $ENV{BOOST_ROOT} STREQUAL "" )
  set( BOOST_ROOT $ENV{BOOST_ROOT) )
endif()

if ( NOT BOOST_ROOT AND NOT $ENV{BOOSTROOT} STREQUAL "" )
  set( BOOST_ROOT $ENV{BOOSTROOT) )
endif()

file(TO_CMAKE_PATH ${BOOST_ROOT} BOOST_ROOT)

and then just proceed to use BOOST_ROOT as it does now

The same goes for BOOST_INCLUDE_DIR and BOOST_LIBRARY_DIRS

BTW, why is the above path conversion gone in the 2.6 version??


(4)
The two loops over _boost_TEST_VERSIONS are nearly indentical, and it's a 
bit complicated, so I would put that in a macro to make it more readable, 
discriminating the search path just around the call to find_path (where it 
matters)

And not just that:

Under windows, boost is installed on a folder of the form "boost_x_y_z", not 
"boost-x_y_z", yet the suffix is constructed as:

       SET(_boost_PATH_SUFFIX
        boost-${_boost_VER}
      )

Notice the "boost-" instead of "boost_"

So, on what platforms does this additional version search stuff work? I 
certainly doesn't on my windows machine (yes, I tested it).


(5)
One can use cygwin to run other compilers besides gcc. In fact, that's what 
we do in CGAL, so this:

  IF (CYGWIN)
    SET (_boost_COMPILER "-gcc")
  ENDIF (CYGWIN)

just breaks any previous MSVC detection.
Since "-gcc" is already the fallback value I would just remove those lines.

(6)

Also, in at least 2.4.7, MSCV80 is incorrectly set for VC90 (besides 
MSCV90), so the MSVC version discrimination should be reversed and nested:

  if ( MSVC90 )
     ...
  elseif ( MSVC80 )
     ...
  elseif ( MSVC71 )
     ...
  endif()


(7)

I couldn't understand the dicotomy between the cached and non-cached 
versions of the include dirs:

Boost_INCLUDE_DIRS vs Boost_INCLUDE_DIR

What's the choice for? What doesn't the library dir, or for that matter, the 
libraries list offer the same choice?

(8)

The "check minimum version" stuff is not working for me because the 
Boost_VERSION_* variables are undefined by the time they are compared to the 
Boost_FIND_VERSION_* requirement.

Does it work for you there?

(9)
It is documented that this requires CMake 2.5 (which is 2.6 for us end 
users). And later overdocumented that this ships with CMake 2.6 so the 
version is always right.

Well, strictly speaking one can use *this* module with earlier cmake 
versions, such as 2.4.7 which is still largely used in many linuxes, by 
emulating the additional find_package feautres.
That is, instead of calling it like:

find_package(Boost 1.37.1 COMPONENTS thread )

call it like this:

set( Boost_FIND_VERSION 1.37.1 )
set( Boost_FIND_VERSION_MAJOR 1 )
set( Boost_FIND_VERSION_MINOR 37 )
set( Boost_FIND_VERSION_PATCH 1 )
set( Boost_FIND_COMPONENTS thread )

find_package(Boost)

which works just the same with the old find_package (this is in fact what 
I'm doing in CGAL to avoid requiring users to install CMake 2.6 which is 
usually not just a simple apt-get/rmp call in many linuxes)


Best regards


-- 
Fernando Cacciola
SciSoft
http://scisoft-consulting.com
http://fcacciola.50webs.com
http://groups.google.com/group/cppba