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workaround for cmake's check_cxx_source_compiles

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evaleev committed Sep 1, 2017
1 parent 4d9bc81 commit 7f4507519cbd6508940baae92853ab5f46cb847e
Showing with 109 additions and 0 deletions.
  1. +5 −0 CMakeLists.txt
  2. +104 −0 cmake/modules/AddOptions.cmake
# Add module directory and modules =============================================
@@ -27,6 +28,10 @@ include(CMakePackageConfigHelpers)
# workaround for cmake bug: CheckCXXSourceCompiles does not respect CXX_STANDARD
# see
# Set install paths ============================================================
@@ -0,0 +1,104 @@
# see
# - Add options without repeating them on the command line
# Synopsis:
# add_options (lang build opts)
# where:
# lang Name of the language whose compiler should receive the
# options, e.g. CXX. If a comma-separated list is received
# then the option is added for all those languages. Use the
# special value ALL_LANGUAGES for these languages: CXX, C
# and Fortran
# build Kind of build to which this options should apply,
# such as DEBUG and RELEASE. This can also be a comma-
# separated list. Use the special value ALL_BUILDS to apply
# to all builds.
# opts List of options to add. Each should be quoted.
# Example:
# add_options (CXX RELEASE "-O3" "-DNDEBUG" "-Wall")
function (add_options langs builds)
# special handling of empty language specification
if ("${langs}" STREQUAL "ALL_LANGUAGES")
set (langs CXX C Fortran)
endif ("${langs}" STREQUAL "ALL_LANGUAGES")
foreach (lang IN LISTS langs)
# prepend underscore if necessary
foreach (build IN LISTS builds)
if (NOT ("${build}" STREQUAL "ALL_BUILDS"))
set (_bld "_${build}")
string (TOUPPER "${_bld}" _bld)
else (NOT ("${build}" STREQUAL "ALL_BUILDS"))
set (_bld "")
endif (NOT ("${build}" STREQUAL "ALL_BUILDS"))
# if we want everything in the "global" flag, then simply
# ignore the build type here and go add everything to that one
set (_bld "")
endif ()
foreach (_opt IN LISTS ARGN)
set (_var "CMAKE_${lang}_FLAGS${_bld}")
#message (STATUS "Adding \"${_opt}\" to \${${_var}}")
# remove it first
string (REPLACE "${_opt}" "" _without "${${_var}}")
string (STRIP "${_without}" _without)
# we need to strip this one as well, so they are comparable
string (STRIP "${${_var}}" _stripped)
# if it wasn't there, then add it at the end
if ("${_without}" STREQUAL "${_stripped}")
# don't add any extra spaces if no options yet are set
if (NOT ${_stripped} STREQUAL "")
set (${_var} "${_stripped} ${_opt}")
else (NOT ${_stripped} STREQUAL "")
set (${_var} "${_opt}")
endif (NOT ${_stripped} STREQUAL "")
set (${_var} "${${_var}}" PARENT_SCOPE)
endif ("${_without}" STREQUAL "${_stripped}")
endforeach (_opt)
endforeach (build)
endforeach (lang)
endfunction (add_options lang build)
# set varname to flag unless user has specified something that matches regex
function (set_default_option lang varname flag regex)
# lang is either C, CXX or Fortran
if ("${lang}" STREQUAL "Fortran")
set (letter "F")
else ()
set (letter "${lang}")
endif ()
string (TOUPPER "${CMAKE_BUILD_TYPE}" _build)
if ((NOT ("$ENV{${letter}FLAGS}" MATCHES "${regex}"))
AND (NOT ("${CMAKE_${lang}_FLAGS}" MATCHES "${regex}"))
AND (NOT ("${CMAKE_${lang}_FLAGS_${_build}}" MATCHES "${regex}")))
set (${varname} ${flag} PARENT_SCOPE)
else ()
set (${varname} PARENT_SCOPE)
endif ()
endfunction (set_default_option)
# clear default options as a proxy for not using any default options
# at all. there is one *huge* problem with this: CMake runs the platform
# initialization before executing any line at all in the project and
# there seems to be no way to disable that behaviour, so we cannot really
# distinguish between a platform default and something that the user has
# passed on the command line. the best thing we can do is to all user-
# defined setting if they are something other than the platform default.
macro (no_default_options)
foreach (lang IN ITEMS C CXX Fortran)
if ("${CMAKE_${lang}_FLAGS_${build}}" STREQUAL "${CMAKE_${lang}_FLAGS_${build}_INIT}")
# for some strange reason we cannot clear this flag, only set it to empty
set (CMAKE_${lang}_FLAGS_${build} "")
endif ()
endforeach (build)
endforeach (lang)
endmacro (no_default_options)

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