CMAKE: switch between clang / g++ and libc++ /libstdc++

Question

This is my first cmake file. I have a linux system with both clang and g++. Also libc++ is installed. I develop on Mac (xcode) but deploy to linux. I am writing a cmake file in which I can pick either clang or g++ and libc++ or libstdc++. So 4 possible combinations.

I figured out how to select the compiler and force c++11 on it, but I can't figure out how to specify the standard library. Any suggestions?

This is what I have so far:

## cmake ###
cmake_minimum_required (VERSION 3.5)

#set project directories
set(ProjectDirectory ${CMAKE_SOURCE_DIR}) #.../Project/
set(BuildDirectory ${ProjectDirectory}/Build)
set(ProductDirectory ${ProjectDirectory}/Products)
set(sourceDirectory ${ProjectDirectory}/Source)

#print project directories
message(${ProjectDirectory})
message(${BuildDirectory})
message(${ProductDirectory})

#configure cmake
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${ProductDirectory})
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${ProductDirectory})
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${ProductDirectory})

set(CMAKE_VERBOSE_MAKEFILE on)

#compiler and standard library settings
set(CMAKE_CXX_COMPILER "clang++")
set(CMAKE_CXX_STANDARD 11)
#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -v -stdlib=libc++")
        #libstdc++ #linux
        #libc++    #OS X

#compiler flags
SET( CompilerFlags  " ")
#SET( CompilerFlags  "${CompilerFlags} -stdlib=libc++" )
SET( CompilerFlags  "${CompilerFlags} -Wno-unknown-pragmas" )
SET( CompilerFlags  "${CompilerFlags} -Wall" )
SET( CompilerFlags  "${CompilerFlags} -Wextra" )

set (CMAKE_CXX_FLAGS ${CompilerFlags})

#linker flags
#set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++ -lc++abi")

#message(${CMAKE_CXX_FLAGS})

##################
### Libraries ###
################
### common library ###
project(common)

#message(STATUS ${CMAKE_CXX_FLAGS})

#source files
#set (commonSource ${sourceDirectory}/Object/object.cpp) #specify specific files
file(GLOB_RECURSE commonSource ${sourceDirectory}/Object/*.cpp) # recursive

#targets
add_library (common STATIC ${commonSource})

#target_compile_options (common PUBLIC ${CompilerFlags})


#####################
### Applications ###
###################
### Hello project ###
project (hello)

#source files
#set (helloSource ${sourceDirectory}/main.cpp)

#targets
#add_executable (hello ${helloSource})

#linking
#target_link_libraries (hello common)


#install(TARGETS common DESTINATION ${ProductDirectory})

I run this command on a console

../Project/Build$ rm -r *; rm -r ../Products/*; cmake ..; make VERBOSE=1;

My folder structure is:

Project
    Source
    Build
    Products
    CMakeLists.txt

I have also noticed that the compiler flags are sometimes ignored and only used when I run cmake and make a second time.

Also, I use a lot of #warning todo in my code How can I disable these warnings during compilation?

Answer 1

It's a little tricky because I don't believe CMake has a built in way to select a standard library. What I do is pass it into the linker flags. e.g.

set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++ -lc++abi")

CMake does, however, support setting the compiler:

set(CMAKE_CXX_COMPILER "clang++")