[mlpack-git] master: Add FORCE_CXX11 option to work around deficiencies in CMake. (a2d45eb)

[gitdub at mlpack.org]

Repository : https://github.com/mlpack/mlpack
On branch  : master
Link       : https://github.com/mlpack/mlpack/compare/ebdb5abeaa3fd621a06ae663862bb72df76d2b40...a2d45ebc93d175602500df8136d54328399e40a8

>---------------------------------------------------------------

commit a2d45ebc93d175602500df8136d54328399e40a8
Author: Ryan Curtin <ryan at ratml.org>
Date:   Wed Oct 5 10:19:45 2016 -0400

    Add FORCE_CXX11 option to work around deficiencies in CMake.
    
    This is meant to address #796.


>---------------------------------------------------------------

a2d45ebc93d175602500df8136d54328399e40a8
 CMakeLists.txt            | 38 +++++++++++++++++++++++---------------
 src/mlpack/CMakeLists.txt |  5 -----
 2 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e0f18c3..eb25187 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,21 +1,6 @@
 cmake_minimum_required(VERSION 2.8.5)
 project(mlpack C CXX)
 
-# Ensure that we have a C++11 compiler.  In newer versions of CMake, this is
-# done with target_compile_features() when the mlpack library target is added in
-# src/mlpack/CMakeLists.txt.
-if (${CMAKE_MAJOR_VERSION} LESS 3 OR
-    (${CMAKE_MAJOR_VERSION} EQUAL 3 AND ${CMAKE_MINOR_VERSION} LESS 1))
-  # Older versions of CMake do not support target_compile_features(), so we have
-  # to use something kind of hacky.
-  include(CMake/CXX11.cmake)
-  check_for_cxx11_compiler(HAS_CXX11)
-  if(NOT HAS_CXX11)
-    message(FATAL_ERROR "No C++11 compiler available!")
-  endif()
-  enable_cxx11()
-endif()
-
 # First, define all the compilation options.
 # We default to debugging mode for developers.
 option(DEBUG "Compile with debugging information." OFF)
@@ -31,8 +16,31 @@ option(BUILD_WITH_COVERAGE
     "Build with support for code coverage tools (gcc only)." OFF)
 option(MATHJAX
     "Use MathJax for HTML Doxygen output (disabled by default)." OFF)
+option(FORCE_CXX11
+    "Don't check that the compiler supports C++11, just assume it.  Make sure \
+     to specify any necessary flag to enable C++11 as part of CXXFLAGS." OFF)
 enable_testing()
 
+# Ensure that we have a C++11 compiler.  In newer versions of CMake, this is
+# done with target_compile_features() when the mlpack library target is added in
+# src/mlpack/CMakeLists.txt.
+if ((${CMAKE_MAJOR_VERSION} LESS 3 OR
+    (${CMAKE_MAJOR_VERSION} EQUAL 3 AND ${CMAKE_MINOR_VERSION} LESS 1))
+    AND NOT FORCE_CXX11)
+  # Older versions of CMake do not support target_compile_features(), so we have
+  # to use something kind of hacky.
+  include(CMake/CXX11.cmake)
+  check_for_cxx11_compiler(HAS_CXX11)
+  if(NOT HAS_CXX11)
+    message(FATAL_ERROR "No C++11 compiler available!")
+  endif()
+  enable_cxx11()
+elseif (NOT FORCE_CXX11)
+  # Use the newer C++11 checks.
+  include(../../CMake/NewCXX11.cmake)
+endif ()
+
+
 # Include modules in the CMake directory.
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/CMake")
 
diff --git a/src/mlpack/CMakeLists.txt b/src/mlpack/CMakeLists.txt
index 82663a1..cc9008b 100644
--- a/src/mlpack/CMakeLists.txt
+++ b/src/mlpack/CMakeLists.txt
@@ -23,11 +23,6 @@ endif ()
 # are set in the root CMakeLists.txt.
 add_library(mlpack ${MLPACK_SRCS})
 
-if (NOT (${CMAKE_MAJOR_VERSION} LESS 3 OR
-        (${CMAKE_MAJOR_VERSION} EQUAL 3 AND ${CMAKE_MINOR_VERSION} LESS 1)))
-  include(../../CMake/NewCXX11.cmake)
-endif ()
-
 # Generate export symbols for Windows, instead of adding __declspec(dllimport)
 # and __declspec(dllexport) everywhere.  However, those modifiers are still
 # necessary for global variables (of which there are a few in mlpack).