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# This script creates a function, enable_cpp11_for_target(), which checks if your
# compiler has C++11 support and enables it if it does.
cmake_minimum_required(VERSION 2.8.12)
if (POLICY CMP0054)
cmake_policy(SET CMP0054 NEW)
endif()
set(_where_is_cmake_utils_dir ${CMAKE_CURRENT_LIST_DIR})
function(enable_cpp11_for_target target_name)
# Set to false unless we find out otherwise in the code below.
set(COMPILER_CAN_DO_CPP_11 0)
macro(test_compiler_for_cpp11)
message(STATUS "Building a C++11 test project to see if your compiler supports C++11")
try_compile(test_for_cpp11_worked ${PROJECT_BINARY_DIR}/cpp11_test_build
${_where_is_cmake_utils_dir}/test_for_cpp11 cpp11_test)
if (test_for_cpp11_worked)
message(STATUS "C++11 activated.")
set(COMPILER_CAN_DO_CPP_11 1)
else()
set(COMPILER_CAN_DO_CPP_11 0)
message(STATUS "********** Your compiler failed to build a C++11 project. C++11 is required to use all parts of dlib! **********")
endif()
endmacro()
# Now turn on the appropriate compiler switch to enable C++11 if you have a
# C++11 compiler. In CMake 3.1 there is a simple flag you can set, but earlier
# verions of CMake are not so convenient.
if (CMAKE_VERSION VERSION_LESS "3.1.2")
if(CMAKE_COMPILER_IS_GNUCXX)
execute_process(COMMAND ${CMAKE_CXX_COMPILER} -dumpversion OUTPUT_VARIABLE GCC_VERSION)
if (GCC_VERSION VERSION_GREATER 4.8 OR GCC_VERSION VERSION_EQUAL 4.8)
message(STATUS "C++11 activated.")
target_compile_options(${target_name} PUBLIC "-std=gnu++11")
set(COMPILER_CAN_DO_CPP_11 1)
endif()
elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
execute_process( COMMAND ${CMAKE_CXX_COMPILER} --version OUTPUT_VARIABLE clang_full_version_string )
string (REGEX REPLACE ".*clang version ([0-9]+\\.[0-9]+).*" "\\1" CLANG_VERSION ${clang_full_version_string})
if (CLANG_VERSION VERSION_GREATER 3.3)
message(STATUS "C++11 activated.")
target_compile_options(${target_name} PUBLIC "-std=c++11")
set(COMPILER_CAN_DO_CPP_11 1)
endif()
else()
# Since we don't know what compiler this is just try to build a c++11 project and see if it compiles.
test_compiler_for_cpp11()
endif()
else()
# Set a flag if the compiler you are using is capable of providing C++11 features.
get_property(cxx_features GLOBAL PROPERTY CMAKE_CXX_KNOWN_FEATURES)
if (";${cxx_features};" MATCHES ";cxx_rvalue_references;" AND
";${cxx_features};" MATCHES ";cxx_variadic_templates;" AND
";${cxx_features};" MATCHES ";cxx_lambdas;" AND
";${cxx_features};" MATCHES ";cxx_defaulted_move_initializers;" AND
";${cxx_features};" MATCHES ";cxx_delegating_constructors;" AND
";${cxx_features};" MATCHES ";cxx_thread_local;" AND
";${cxx_features};" MATCHES ";cxx_constexpr;" AND
";${cxx_features};" MATCHES ";cxx_decltype_incomplete_return_types;" AND
";${cxx_features};" MATCHES ";cxx_auto_type;")
set(COMPILER_CAN_DO_CPP_11 1)
# Tell cmake that we need C++11 for dlib
target_compile_features(${target_name}
PUBLIC
cxx_rvalue_references
cxx_variadic_templates
cxx_lambdas
cxx_defaulted_move_initializers
cxx_delegating_constructors
cxx_thread_local
cxx_constexpr
# cxx_decltype_incomplete_return_types # purposfully commented out because cmake errors out on this when using visual studio and cmake 3.8.0
cxx_auto_type
)
if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
# Sometimes clang will lie and report that it supports C++11 when
# really it doesn't support thread_local. So check for that.
test_compiler_for_cpp11()
else()
message(STATUS "C++11 activated.")
endif()
endif()
endif()
# Always enable whatever partial C++11 support we have, even if it isn't full
# support, and just hope for the best.
if (NOT COMPILER_CAN_DO_CPP_11)
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
if(COMPILER_SUPPORTS_CXX11)
message(STATUS "C++11 activated (compiler doesn't have full C++11 support).")
target_compile_options(${target_name} PUBLIC "-std=c++11")
elseif(COMPILER_SUPPORTS_CXX0X)
message(STATUS "C++0x activated (compiler doesn't have full C++11 support).")
target_compile_options(${target_name} PUBLIC "-std=c++0x")
endif()
endif()
endfunction()
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