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Use CMAKE_CXX_STANDARD when available (#953)
* Use CMAKE_CXX_STANDARD when available If the use has provided the variable CMAKE_CXX_STANDARD use that instead of providing a default cache variable. * Typo
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@ -1,5 +1,8 @@
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cmake_minimum_required(VERSION 3.1.3...3.16)
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list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/")
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include(guidelineSupportLibrary)
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project(GSL VERSION 3.1.0 LANGUAGES CXX)
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include(ExternalProject)
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@ -8,39 +11,30 @@ find_package(Git)
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# Use GNUInstallDirs to provide the right locations on all platforms
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include(GNUInstallDirs)
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# creates a library GSL which is an interface (header files only)
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# Creates a library GSL which is an interface (header files only)
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add_library(GSL INTERFACE)
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# determine whether this is a standalone project or included by other projects
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# NOTE: If you want to use GSL prefer to link against GSL using this alias target
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# EX:
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# target_link_libraries(foobar PRIVATE Microsoft.GSL::GSL)
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#
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# Add Microsoft.GSL::GSL alias for GSL so that dependents can be agnostic about
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# whether GSL was added via `add_subdirectory` or `find_package`
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add_library(Microsoft.GSL::GSL ALIAS GSL)
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# Determine whether this is a standalone project or included by other projects
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set(GSL_STANDALONE_PROJECT OFF)
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if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
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set(GSL_STANDALONE_PROJECT ON)
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endif ()
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set(GSL_CXX_STANDARD "14" CACHE STRING "Use c++ standard")
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set(GSL_CXX_STD "cxx_std_${GSL_CXX_STANDARD}")
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if (MSVC)
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set(GSL_CXX_STD_OPT "-std:c++${GSL_CXX_STANDARD}")
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else()
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set(GSL_CXX_STD_OPT "-std=c++${GSL_CXX_STANDARD}")
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endif()
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# when minimum version required is 3.8.0 remove if below
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# both branches do exactly the same thing
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if (CMAKE_VERSION VERSION_LESS 3.7.9)
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include(CheckCXXCompilerFlag)
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CHECK_CXX_COMPILER_FLAG("${GSL_CXX_STD_OPT}" COMPILER_SUPPORTS_CXX_STANDARD)
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# This GSL implementation generally assumes a platform that implements C++14 support.
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set(gsl_min_cxx_standard "14")
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if(COMPILER_SUPPORTS_CXX_STANDARD)
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target_compile_options(GSL INTERFACE "${GSL_CXX_STD_OPT}")
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else()
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message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no c++${GSL_CXX_STANDARD} support. Please use a different C++ compiler.")
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endif()
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else ()
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target_compile_features(GSL INTERFACE "${GSL_CXX_STD}")
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# on *nix systems force the use of -std=c++XX instead of -std=gnu++XX (default)
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set(CMAKE_CXX_EXTENSIONS OFF)
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if (GSL_STANDALONE_PROJECT)
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gsl_set_default_cxx_standard(${gsl_min_cxx_standard})
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else()
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gsl_client_set_cxx_standard(${gsl_min_cxx_standard})
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endif()
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# add definitions to the library and targets that consume it
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@ -111,10 +105,6 @@ else()
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endif()
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install(FILES ${CMAKE_CURRENT_BINARY_DIR}/Microsoft.GSLConfigVersion.cmake DESTINATION ${CMAKE_INSTALL_DATADIR}/cmake/Microsoft.GSL)
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# Add Microsoft.GSL::GSL alias for GSL so that dependents can be agnostic about
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# whether GSL was added via `add_subdirectory` or `find_package`
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add_library(Microsoft.GSL::GSL ALIAS GSL)
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option(GSL_TEST "Generate tests." ${GSL_STANDALONE_PROJECT})
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if (GSL_TEST)
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enable_testing()
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61
cmake/guidelineSupportLibrary.cmake
Normal file
61
cmake/guidelineSupportLibrary.cmake
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@ -0,0 +1,61 @@
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# This cmake module is meant to hold helper functions/macros
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# that make maintaining the cmake build system much easier.
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# This is especially helpful since gsl needs to provide coverage
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# for multiple versions of cmake.
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#
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# Any functions/macros should have a gsl_* prefix to avoid problems
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if (DEFINED guideline_support_library_include_guard)
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return()
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endif()
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set(guideline_support_library_include_guard ON)
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function(gsl_set_default_cxx_standard min_cxx_standard)
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set(GSL_CXX_STANDARD "${min_cxx_standard}" CACHE STRING "Use c++ standard")
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set(GSL_CXX_STD "cxx_std_${GSL_CXX_STANDARD}")
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if (MSVC)
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set(GSL_CXX_STD_OPT "-std:c++${GSL_CXX_STANDARD}")
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else()
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set(GSL_CXX_STD_OPT "-std=c++${GSL_CXX_STANDARD}")
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endif()
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# when minimum version required is 3.8.0 remove if below
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# both branches do exactly the same thing
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if (CMAKE_VERSION VERSION_LESS 3.7.9)
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include(CheckCXXCompilerFlag)
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CHECK_CXX_COMPILER_FLAG("${GSL_CXX_STD_OPT}" COMPILER_SUPPORTS_CXX_STANDARD)
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if(COMPILER_SUPPORTS_CXX_STANDARD)
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target_compile_options(GSL INTERFACE "${GSL_CXX_STD_OPT}")
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else()
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message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no c++${GSL_CXX_STANDARD} support. Please use a different C++ compiler.")
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endif()
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else()
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target_compile_features(GSL INTERFACE "${GSL_CXX_STD}")
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# on *nix systems force the use of -std=c++XX instead of -std=gnu++XX (default)
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set(CMAKE_CXX_EXTENSIONS OFF)
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endif()
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endfunction()
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# The best way for a project to specify the GSL's C++ standard is by the client specifying
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# the CMAKE_CXX_STANDARD. However, this isn't always ideal. Since the CMAKE_CXX_STANDARD is
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# tied to the cmake version. And many projects have low cmake minimums.
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#
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# So provide an alternative approach in case that doesn't work.
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function(gsl_client_set_cxx_standard min_cxx_standard)
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if (DEFINED CMAKE_CXX_STANDARD)
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if (${CMAKE_CXX_STANDARD} VERSION_LESS ${min_cxx_standard})
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message(FATAL_ERROR "GSL: Requires at least CXX standard ${min_cxx_standard}, user provided ${CMAKE_CXX_STANDARD}")
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endif()
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# Set the GSL standard to what the client desires
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set(GSL_CXX_STANDARD "${CMAKE_CXX_STANDARD}" PARENT_SCOPE)
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# Exit out early to avoid extra unneccessary work
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return()
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endif()
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# Otherwise pick a reasonable default
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gsl_set_default_cxx_standard(${min_cxx_standard})
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endfunction()
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