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Use CMAKE_CXX_STANDARD when available (#953)

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* 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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hdf89shfdfs 2020-11-16 17:05:33 -05:00 committed by GitHub
parent 959ce58bbc
commit 475b785d2c
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2 changed files with 80 additions and 29 deletions
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48
CMakeLists.txt
View File

@ -1,5 +1,8 @@
cmake_minimum_required(VERSION 3.1.3...3.16)
list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/")
include(guidelineSupportLibrary)
project(GSL VERSION 3.1.0 LANGUAGES CXX)
include(ExternalProject)
@ -8,39 +11,30 @@ find_package(Git)
# Use GNUInstallDirs to provide the right locations on all platforms
include(GNUInstallDirs)
# creates a library GSL which is an interface (header files only)
# Creates a library GSL which is an interface (header files only)
add_library(GSL INTERFACE)
# determine whether this is a standalone project or included by other projects
# NOTE: If you want to use GSL prefer to link against GSL using this alias target
# EX:
# target_link_libraries(foobar PRIVATE Microsoft.GSL::GSL)
#
# Add Microsoft.GSL::GSL alias for GSL so that dependents can be agnostic about
# whether GSL was added via `add_subdirectory` or `find_package`
add_library(Microsoft.GSL::GSL ALIAS GSL)
# Determine whether this is a standalone project or included by other projects
set(GSL_STANDALONE_PROJECT OFF)
if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
set(GSL_STANDALONE_PROJECT ON)
endif ()
set(GSL_CXX_STANDARD "14" CACHE STRING "Use c++ standard")
set(GSL_CXX_STD "cxx_std_${GSL_CXX_STANDARD}")
if (MSVC)
set(GSL_CXX_STD_OPT "-std:c++${GSL_CXX_STANDARD}")
else()
set(GSL_CXX_STD_OPT "-std=c++${GSL_CXX_STANDARD}")
endif()
# when minimum version required is 3.8.0 remove if below
# both branches do exactly the same thing
if (CMAKE_VERSION VERSION_LESS 3.7.9)
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("${GSL_CXX_STD_OPT}" COMPILER_SUPPORTS_CXX_STANDARD)
# This GSL implementation generally assumes a platform that implements C++14 support.
set(gsl_min_cxx_standard "14")
if(COMPILER_SUPPORTS_CXX_STANDARD)
target_compile_options(GSL INTERFACE "${GSL_CXX_STD_OPT}")
else()
message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no c++${GSL_CXX_STANDARD} support. Please use a different C++ compiler.")
endif()
else ()
target_compile_features(GSL INTERFACE "${GSL_CXX_STD}")
# on *nix systems force the use of -std=c++XX instead of -std=gnu++XX (default)
set(CMAKE_CXX_EXTENSIONS OFF)
if (GSL_STANDALONE_PROJECT)
gsl_set_default_cxx_standard(${gsl_min_cxx_standard})
else()
gsl_client_set_cxx_standard(${gsl_min_cxx_standard})
endif()
# add definitions to the library and targets that consume it
@ -111,10 +105,6 @@ else()
endif()
install(FILES ${CMAKE_CURRENT_BINARY_DIR}/Microsoft.GSLConfigVersion.cmake DESTINATION ${CMAKE_INSTALL_DATADIR}/cmake/Microsoft.GSL)
# Add Microsoft.GSL::GSL alias for GSL so that dependents can be agnostic about
# whether GSL was added via `add_subdirectory` or `find_package`
add_library(Microsoft.GSL::GSL ALIAS GSL)
option(GSL_TEST "Generate tests." ${GSL_STANDALONE_PROJECT})
if (GSL_TEST)
enable_testing()

61
cmake/guidelineSupportLibrary.cmake Normal file
View File

@ -0,0 +1,61 @@
# This cmake module is meant to hold helper functions/macros
# that make maintaining the cmake build system much easier.
# This is especially helpful since gsl needs to provide coverage
# for multiple versions of cmake.
#
# Any functions/macros should have a gsl_* prefix to avoid problems
if (DEFINED guideline_support_library_include_guard)
return()
endif()
set(guideline_support_library_include_guard ON)
function(gsl_set_default_cxx_standard min_cxx_standard)
set(GSL_CXX_STANDARD "${min_cxx_standard}" CACHE STRING "Use c++ standard")
set(GSL_CXX_STD "cxx_std_${GSL_CXX_STANDARD}")
if (MSVC)
set(GSL_CXX_STD_OPT "-std:c++${GSL_CXX_STANDARD}")
else()
set(GSL_CXX_STD_OPT "-std=c++${GSL_CXX_STANDARD}")
endif()
# when minimum version required is 3.8.0 remove if below
# both branches do exactly the same thing
if (CMAKE_VERSION VERSION_LESS 3.7.9)
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("${GSL_CXX_STD_OPT}" COMPILER_SUPPORTS_CXX_STANDARD)
if(COMPILER_SUPPORTS_CXX_STANDARD)
target_compile_options(GSL INTERFACE "${GSL_CXX_STD_OPT}")
else()
message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no c++${GSL_CXX_STANDARD} support. Please use a different C++ compiler.")
endif()
else()
target_compile_features(GSL INTERFACE "${GSL_CXX_STD}")
# on *nix systems force the use of -std=c++XX instead of -std=gnu++XX (default)
set(CMAKE_CXX_EXTENSIONS OFF)
endif()
endfunction()
# The best way for a project to specify the GSL's C++ standard is by the client specifying
# the CMAKE_CXX_STANDARD. However, this isn't always ideal. Since the CMAKE_CXX_STANDARD is
# tied to the cmake version. And many projects have low cmake minimums.
#
# So provide an alternative approach in case that doesn't work.
function(gsl_client_set_cxx_standard min_cxx_standard)
if (DEFINED CMAKE_CXX_STANDARD)
if (${CMAKE_CXX_STANDARD} VERSION_LESS ${min_cxx_standard})
message(FATAL_ERROR "GSL: Requires at least CXX standard ${min_cxx_standard}, user provided ${CMAKE_CXX_STANDARD}")
endif()
# Set the GSL standard to what the client desires
set(GSL_CXX_STANDARD "${CMAKE_CXX_STANDARD}" PARENT_SCOPE)
# Exit out early to avoid extra unneccessary work
return()
endif()
# Otherwise pick a reasonable default
gsl_set_default_cxx_standard(${min_cxx_standard})
endfunction()