[question] Boost_<COMPONENT>_Found cmake variables missing ?

[ggulgulia]

Hello there,

Description

• I'm creating conan recipe for OGRE (recipe OGRE #11102) which is an important graphics rendering engine for many applications like games and simulations, including ignition-gazebo etc.
• OGRE relies on boost and the standard boost cmake variables like Boost_THREAD_FOUND , Boost_DATE_TIME_FOUND etc .
• The conan generated FindBoost.cmake doesn't seem to provide the cmake variables because of which the build doesn't work as expected

Comparison with official FindBoost.cmake cmake documentation

• The official cmake for FindBoost.cmake sets these variables .
• I also tried building OGRE with system installed boost and it worked fine since the system installed FindBoost.cmake sets these variables. See line 312 in the attached file (extension changed)
  FindBoost.cmake.txt

Question

• Does conan recipe for boost provide these variables or any variable to verify if a component was found ?
• If not, will CCI consider adding these cmake variables ?
• Is there a recommended short term fix or a recipe that I can look into from another recipe and with which I can work now ?

[prince-chrismc]

doesn't seem to provide the cmake variables because of which the build doesn't work as expected

You are correct they are not provided, I was trying to see if there a reason the might have been mentioned but I as not able.

Does conan recipe for boost provide these variables or any variable to verify if a component was found ?

I have two paths as a community reiviewer

• Using if checks in the CMake for targets if(TARGET Boost::thread)
• Validate the components in the conanfile and assume they are present in CMake

the second option is prefered, since Conan can ensure the correct package is used,

conan-center-index/recipes/wt/all/conanfile.py

Line 98 in 10c8d47

def _required_boost_components(self):

conan-center-index/recipes/gtsam/all/patches/0001-conan-4.0.2.patch

Line 60 in 9a6866e

+ Boost::serialization

[ggulgulia]

Thanks for the response.

The second option seems correct but in the case where the components are searched on CMake level like in OGRE,

 if (NOT Boost_THREAD_FOUND)
        set(OGRE_DEPS_FOUND FALSE)
 else ()
 ...

we will still need set the variable Boost_<COMPONENT>_FOUND for CMake through patches for build to work correctly. Considering Boost is a dependency for many applications, adding patches is not easy especially when the if-else branching is not trivial like in OGRE. It might be worthwhile to provide the standard cmake variable as done by FindBoost.cmake unless there's a strong reason to not provide them.