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IDProjectCategoryView StatusDate SubmittedLast Update
0013439CMakeCMakepublic2012-07-25 17:332016-06-10 14:31
ReporterPieter Swinkels 
Assigned ToPhilip Lowman 
PrioritynormalSeverityminorReproducibilityalways
StatusclosedResolutionmoved 
PlatformLinuxOSUbuntuOS Version12.04
Product VersionCMake 2.8.7 
Target VersionFixed in Version 
Summary0013439: consecutive find_package(Boost ...) statements only find the static lib regardless of Boost_USE_STATIC_LIBS
DescriptionConsecutive find_package(Boost ...) statements for the same Boost component in the same file CMakeLists.txt but

  - the first time with Boost_USE_STATIC_LIBS to ON and
  - the second time with BOOST_USE_STATIC_LIBS to OFF

always finds the static library.
Steps To ReproduceTry something like this:

set(Boost_USE_STATIC_LIBS ON)

find_package(Boost COMPONENTS unit_test_framework REQUIRED)
if (Boost_FOUND)
  include_directories(${Boost_INCLUDE_DIRS})
endif (Boost_FOUND)

# ${BOOST_LIBRARIES} contains the static version of the library

add_executable(my-static-find-package-boost-test main-static.cpp)
target_link_libraries(my-static-find-package-boost-test ${Boost_LIBRARIES})

unset(Boost_LIBRARIES)
message("Boost_LIBRARIES: ${Boost_LIBRARIES}")

set(Boost_USE_STATIC_LIBS OFF)

find_package(Boost COMPONENTS unit_test_framework REQUIRED)
if (Boost_FOUND)
  include_directories(${Boost_INCLUDE_DIRS})
endif (Boost_FOUND)

# ${BOOST_LIBRARIES} still contains the static version of the library

add_executable(my-dynamic-find-package-boost-test main-dynamic.cpp)
target_link_libraries(my-dynamic-find-package-boost-test ${Boost_LIBRARIES})
Additional InformationIt is not that the dynamic library cannot be found. If I uncomment the first invocation, clear the cache (!) and run cmake, the dynamic library is found.
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Issue History
Date ModifiedUsernameFieldChange
2012-07-25 17:33Pieter SwinkelsNew Issue
2012-07-30 02:53Rolf Eike BeerNote Added: 0030151
2012-08-06 15:30Pieter SwinkelsNote Added: 0030178
2012-08-10 16:35Pieter SwinkelsNote Added: 0030213
2012-08-18 15:30Philip LowmanStatusnew => assigned
2012-08-18 15:30Philip LowmanAssigned To => Philip Lowman
2012-10-04 02:08Philip LowmanNote Added: 0031176
2016-06-10 14:28Kitware RobotNote Added: 0042096
2016-06-10 14:28Kitware RobotStatusassigned => resolved
2016-06-10 14:28Kitware RobotResolutionopen => moved
2016-06-10 14:31Kitware RobotStatusresolved => closed

Notes
(0030151)
Rolf Eike Beer   
2012-07-30 02:53   
Your example can't work this way. You need to clear all the internal cache variables of Boost, otherwise it will just reconstruct BOOST_LIBRARIES from the stuff it already found.
(0030178)
Pieter Swinkels   
2012-08-06 15:30   
Thank you for the reply. I would rather not make any assumptions about the internal cache variables so I better split up my CMake file list.

One thing, I found my approach on http://www.cmake.org/pipermail/cmake/2012-February/049175.html [^] so I was surprised to find it not working. On rereading that email, I see that it already warns me about this situation :(

  "IMO, FindBoost.cmake behaves bad in one regard: It accumulates results from different invocations within the same scope. For this reason, you must intermediately unset the Boost_LIBRARIES variable - and probably all further uncached result variables like Boost_INCLUDE_DIRS also."
(0030213)
Pieter Swinkels   
2012-08-10 16:35   
There is a way to invalidate the Boost cache, see the answer to this question: http://stackoverflow.com/questions/11680168/how-can-i-optionally-link-against-static-or-dynamic-boost-library-using-cmake [^] I quote from that answer "To force the FindBoost CMake module to search for the desired libraries again, you have to clear the cache variables Boost_INCLUDE_DIR and Boost_LIBRARY_DIRS".

In my example, if I add the following statements after "set(Boost_USE_STATIC_LIBS OFF)",

unset(Boost_INCLUDE_DIR CACHE)
unset(Boost_LIBRARY_DIRS CACHE)

the shared library is indeed found.
(0031176)
Philip Lowman   
2012-10-04 02:08   
Hmm, did this issue go away when I removed the crazy caching behavior in 2.8.9?
(0042096)
Kitware Robot   
2016-06-10 14:28   
Resolving issue as `moved`.

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