From 843af6f4e9704ea3048ec74993d2fb2ec0b2351e Mon Sep 17 00:00:00 2001
From: Hugues Delorme <delorme.hugues@fougue.pro>
Date: Thu, 16 Mar 2017 16:41:13 +0100
Subject: [PATCH] cmake: enable c++11 when required

---
 CMakeLists.txt                             |  9 ++++-----
 benchmarks/benchmark_lib3mf/CMakeLists.txt |  6 ++----
 examples/CMakeLists.txt                    |  2 ++
 scripts/enable_cxx11.cmake                 | 18 ++++++++++++++++++
 tests/fake_support/CMakeLists.txt          |  2 ++
 5 files changed, 28 insertions(+), 9 deletions(-)
 create mode 100644 scripts/enable_cxx11.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2a6de08..04f40eb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,6 +30,8 @@
 cmake_minimum_required(VERSION 2.8)
 #cmake_policy(SET CMP0018 NEW)
 
+project(gmio)
+
 include(CheckIncludeFiles)
 include(CheckFunctionExists)
 include(CheckSymbolExists)
@@ -37,7 +39,6 @@ include(CheckCSourceCompiles)
 include(CheckTypeSize)
 include(CMakeDependentOption)
 
-project(gmio)
 set(GMIO_VERSION_MAJOR 0)
 set(GMIO_VERSION_MINOR 4)
 set(GMIO_VERSION_PATCH 0)
@@ -162,7 +163,7 @@ if(CMAKE_C_COMPILER_IS_GCC_COMPATIBLE)
     # Disable warnings -Wno-missing-braces -Wno-missing-field-initializers
     # in case GCC wrongly warns about universal zero initializer {0}
     # See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
-    set(CMAKE_REQUIRED_FLAGS "${CMAKE_C_FLAGS} -Werror=missing-braces")
+    set(CMAKE_REQUIRED_FLAGS "-Werror=missing-braces")
     check_c_source_compiles(
         "struct data { char array[128]; };
          int main() {
@@ -170,7 +171,7 @@ if(CMAKE_C_COMPILER_IS_GCC_COMPATIBLE)
              return d.array[0];
          }"
         GMIO_GCC_DOESNT_WARN_UNIVERSAL_0_INITIALIZER)
-    set(CMAKE_REQUIRED_FLAGS "${CMAKE_C_FLAGS}") # Restore CMAKE_REQUIRED_FLAGS
+    set(CMAKE_REQUIRED_FLAGS) # Popup changes
     if (NOT GMIO_GCC_DOESNT_WARN_UNIVERSAL_0_INITIALIZER)
         set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-missing-braces -Wno-missing-field-initializers")
     endif()
@@ -214,8 +215,6 @@ if(MSVC)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /Oi")
 endif()
 
-set(CMAKE_REQUIRED_FLAGS "${CMAKE_C_FLAGS}")
-
 # Some compilers (like GCC v4.9) don't disable <stdint.h> when needed
 check_include_files(stdint.h GMIO_HAVE_STDINT_H)
 
diff --git a/benchmarks/benchmark_lib3mf/CMakeLists.txt b/benchmarks/benchmark_lib3mf/CMakeLists.txt
index e27c071..4276797 100644
--- a/benchmarks/benchmark_lib3mf/CMakeLists.txt
+++ b/benchmarks/benchmark_lib3mf/CMakeLists.txt
@@ -27,13 +27,11 @@
 ## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #############################################################################
 
+include(../../scripts/enable_cxx11.cmake)
+
 set(ROOTDIR_LIB3MF ${CMAKE_SOURCE_DIR} CACHE PATH
     "Directory where the Lib3MF library resides")
 
-if(CMAKE_C_COMPILER_IS_GCC_COMPATIBLE)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-endif()
-
 include_directories(${ROOTDIR_LIB3MF}/Include)
 add_executable(benchmark_lib3mf main.cpp ${COMMONS_FILES})
 
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index ef9159d..0e75242 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -27,6 +27,8 @@
 ## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #############################################################################
 
+include(../scripts/enable_cxx11.cmake)
+
 include_directories(${CMAKE_SOURCE_DIR}/src)
 include_directories(${CMAKE_BINARY_DIR}/src/gmio_core) # For cmake generated headers
 include_directories(${CMAKE_SOURCE_DIR}/tests/fake_support/opencascade)
diff --git a/scripts/enable_cxx11.cmake b/scripts/enable_cxx11.cmake
new file mode 100644
index 0000000..2503c21
--- /dev/null
+++ b/scripts/enable_cxx11.cmake
@@ -0,0 +1,18 @@
+include(CheckCXXCompilerFlag)
+
+if(CMAKE_COMPILER_IS_GNUCXX
+       OR CMAKE_CXX_COMPILER MATCHES ".*clang")
+    check_cxx_compiler_flag("-std=c++11" GMIO_COMPILER_SUPPORTS_CXX11)
+    if(GMIO_COMPILER_SUPPORTS_CXX11)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+    else()
+        check_cxx_compiler_flag("-std=c++0x" GMIO_COMPILER_SUPPORTS_CXX0X)
+        if(GMIO_COMPILER_SUPPORTS_CXX0X)
+            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
+        else()
+            message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support")
+        endif()
+    endif()
+endif()
+
+# Note : cmake 3.1 introduced set_property(TARGET tgt PROPERTY CXX_STANDARD 11)
diff --git a/tests/fake_support/CMakeLists.txt b/tests/fake_support/CMakeLists.txt
index 6dd8b2e..c994eeb 100644
--- a/tests/fake_support/CMakeLists.txt
+++ b/tests/fake_support/CMakeLists.txt
@@ -27,6 +27,8 @@
 ## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #############################################################################
 
+include(../../scripts/enable_cxx11.cmake)
+
 file(GLOB  GMIO_FAKEOCC_HEADERS  opencascade/*.hxx  opencascade/*.h)
 set(GMIO_FAKEOCC_HEADERS  ${GMIO_FAKEOCC_HEADERS})