Cmake failed to find Threads package with cryptic error message - cmake

Question

I'm trying to configure with following CMakeLists.txt:
cmake_minimum_required(VERSION 3.2)
project(MotionBlow CXX)
find_package(Threads REQUIRED)
find_package(Boost COMPONENTS system program_options REQUIRED)
include(gtest.cmake)
add_executable(motionBlow src/blow.cpp)
target_include_directories(motionBlow PUBLIC include)
target_link_libraries(motionBlow RTIMULib ${Boost_LIBRARIES})
set_property(TARGET motionBlow PROPERTY CXX_STANDARD 14)
add_executable(chat_client src/chat_client.cpp)
target_include_directories(chat_client PUBLIC include)
target_link_libraries(chat_client ${Boost_LIBRARIES} Threads::Threads)
set_property(TARGET chat_client PROPERTY CXX_STANDARD 14)
add_executable(chat_server src/chat_server.cpp)
target_include_directories(chat_server PUBLIC include)
target_link_libraries(chat_server ${Boost_LIBRARIES} Threads::Threads)
set_property(TARGET chat_server PROPERTY CXX_STANDARD 14)
enable_testing()
add_executable(matrixTest test/MatrixTest.cpp src/Matrix.cpp)
target_include_directories(matrixTest PUBLIC include ${GTEST_INCLUDE_DIR})
target_link_libraries(matrixTest ${GTEST_LIBRARY} Threads::Threads)
set_property(TARGET matrixTest PROPERTY CXX_STANDARD 14)
On ubunutu 16.04 it works ok, but both on raspberry pi with Raspbian 8.0/Cmake 3.6.2 and on ubuntu 15.10/Cmake 3.2.2 I get
CMake Error at /usr/share/cmake-3.2/Modules/FindPackageHandleStandardArgs.cmake:138 (message):
Could NOT find Threads (missing: Threads_FOUND)
Call Stack (most recent call first):
/usr/share/cmake-3.2/Modules/FindPackageHandleStandardArgs.cmake:374 (_FPHSA_FAILURE_MESSAGE)
/usr/share/cmake-3.2/Modules/FindThreads.cmake:204 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
CMakeLists.txt:4 (find_package)
Unfortunately, error log contains only this:
Determining if files pthread.h exist failed with the following output:
Source:
/* */
#include <pthread.h>
int main(void){return 0;}
So I have no idea how to get this fixed. Any ideas? Is my CMakelists.txt missing something or should I get a missing package?

Answer 1

Taking your code I could reproduce your error and it seems to be a follow-up error from this:
-- Looking for include file pthread.h
CMake Error at /usr/share/cmake-3.2/Modules/CheckIncludeFiles.cmake:74 (try_compile):
Unknown extension ".c" for file
try_compile() works only for enabled languages. Currently these are:
CXX
See project() command to enable other languages.
Two possible solutions:
Add C to your project languages:
project(MotionBlow C CXX)
Add .c extension a valid C++ file:
MotionBlowMakeRulesOverwrite.cmake
list(APPEND CMAKE_CXX_SOURCE_FILE_EXTENSIONS c)
CMakeLists.txt
cmake_minimum_required(VERSION 3.2)
set(CMAKE_USER_MAKE_RULES_OVERRIDE "MotionBlowMakeRulesOverwrite.cmake")
project(MotionBlow CXX)
If none of this works, check that pthread is installed:
sudo apt-get install libpthread-stubs0-dev
References
Tell CMake to use C++ compiler for C files coming from CMake?
Unable to locate package pthread