[libcxx] Prefer C++14 over C++11 when building libc++experimental.
Summary:
Currently libc++experimental builds with C++11. This patch changes that to C++14 when supported by the compiler. Although nothing currently requires C++14 the upcoming <experimental/memory_resource> implementation would benefit from it. [1]
Note that libc++.so continues to build with C++11 and is unaffected by this change.
[1] <experimental/memory_resource> provides global resources which must exist for the entire lifetime of the program. In order to ensure that a global resource can be used during program termination there destructors must never be invoked. The only way to do this, while also allowing "constant initialization", is to use a C++14 union.
Reviewers: mclow.lists
Subscribers: pete, cfe-commits
Differential Revision: http://reviews.llvm.org/D19992
llvm-svn: 269070
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: a5e201fd5570baa620cd266a73c156420f471ba8
diff --git a/cmake/Modules/HandleLibcxxFlags.cmake b/cmake/Modules/HandleLibcxxFlags.cmake
index bb886fa..b8ea134 100644
--- a/cmake/Modules/HandleLibcxxFlags.cmake
+++ b/cmake/Modules/HandleLibcxxFlags.cmake
@@ -35,6 +35,11 @@
endforeach()
endmacro(remove_flags)
+macro(check_flag_supported flag)
+ mangle_name("${flag}" flagname)
+ check_cxx_compiler_flag("${flag}" "LIBCXX_SUPPORTS_${flagname}_FLAG")
+endmacro()
+
# Add a macro definition if condition is true.
macro(define_if condition def)
if (${condition})
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index 1d38304..05127bd 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -142,9 +142,15 @@
file(GLOB LIBCXX_EXPERIMENTAL_SOURCES ../src/experimental/*.cpp)
add_library(cxx_experimental STATIC ${LIBCXX_EXPERIMENTAL_SOURCES})
target_link_libraries(cxx_experimental cxx)
+
+ set(experimental_flags "${LIBCXX_COMPILE_FLAGS}")
+ check_flag_supported(-std=c++14)
+ if (NOT MSVC AND LIBCXX_SUPPORTS_STD_EQ_CXX14_FLAG)
+ string(REPLACE "-std=c++11" "-std=c++14" experimental_flags "${LIBCXX_COMPILE_FLAGS}")
+ endif()
set_target_properties(cxx_experimental
PROPERTIES
- COMPILE_FLAGS "${LIBCXX_COMPILE_FLAGS}"
+ COMPILE_FLAGS "${experimental_flags}"
OUTPUT_NAME "c++experimental"
)
endif()