Open the Cmake file to be able to compile with the compiler version the user wants

[viboes]

The CMAKE file lets think that we can compile with C++11, but GSL is a C++14 library.

    include(CheckCXXCompilerFlag)
    CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPILER_SUPPORTS_CXX14)
    CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
    if(COMPILER_SUPPORTS_CXX14)
        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -Wall -Wno-missing-braces")
    elseif(COMPILER_SUPPORTS_CXX11)
        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wno-missing-braces")
    else()
      message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
endif()

In addition the CMake file forces the C++ version depending on the compiler ability.
I don't know how to force the compilation with c++1z or even C++11, other than hacking the CMake file.

Any help here will be welcome.

It is up to the user to choose with which compiler and with which version the GSL library must be compiled.

[tamaskenez]

You could use the official CMAKE_CXX_STANDARD variable but

• it supports only 98, 11 and 14 (and you seem to need 1z)
• it works only with CMake >= 3.1

So you need to introduce a user variable, similar to CMAKE_CXX_STANDARD, say GSL_CXX_STANDARD:

if(NOT DEFINED GSL_CXX_STANDARD)
    include(CheckCXXCompilerFlag)
    CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPILER_SUPPORTS_CXX14)
    CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
    if(COMPILER_SUPPORTS_CXX14)
        set(GSL_CXX_STANDARD 14)
    elseif(COMPILER_SUPPORTS_CXX11)
        set(GSL_CXX_STANDARD 11)
    else()
        message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
    endif()
endif()
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++${GSL_CXX_STANDARD} -Wall -Wno-missing-braces")

The user can configure like this:

cmake ... -DGSL_CXX_STANDARD=1z ...