From a4afa90d161faab385a77f0e2764fb13ff3b9484 Mon Sep 17 00:00:00 2001
From: Christoph Hertzberg <chtz@informatik.uni-bremen.de>
Date: Fri, 19 Oct 2018 17:20:51 +0200
Subject: [PATCH] bug #1606: Explicitly set the standard before
 find_package(StandardMathLibrary). Also replace EIGEN_COMPILER_SUPPORT_CXX11
 in favor of EIGEN_COMPILER_SUPPORT_CPP11.

---
 CMakeLists.txt                      | 38 ++++++++++++++++++++---------
 cmake/EigenConfigureTesting.cmake   |  5 ----
 doc/special_examples/CMakeLists.txt |  1 -
 unsupported/test/CMakeLists.txt     |  5 ++--
 4 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 48a574f88..2bfb6d560 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -67,6 +67,33 @@ include(GNUInstallDirs)
 
 set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
 
+
+option(EIGEN_TEST_CXX11 "Enable testing with C++11 and C++11 features (e.g. Tensor module)." OFF)
+
+
+macro(ei_add_cxx_compiler_flag FLAG)
+  string(REGEX REPLACE "-" "" SFLAG1 ${FLAG})
+  string(REGEX REPLACE "\\+" "p" SFLAG ${SFLAG1})
+  check_cxx_compiler_flag(${FLAG} COMPILER_SUPPORT_${SFLAG})
+  if(COMPILER_SUPPORT_${SFLAG})
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${FLAG}")
+  endif()
+endmacro(ei_add_cxx_compiler_flag)
+
+check_cxx_compiler_flag("-std=c++11" EIGEN_COMPILER_SUPPORT_CPP11)
+
+if(EIGEN_TEST_CXX11)
+  set(CMAKE_CXX_STANDARD 11)
+  set(CMAKE_CXX_EXTENSIONS OFF)
+  if(EIGEN_COMPILER_SUPPORT_CPP11)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+  endif()
+else()
+  #set(CMAKE_CXX_STANDARD 03)
+  #set(CMAKE_CXX_EXTENSIONS OFF)
+  ei_add_cxx_compiler_flag("-std=c++03")
+endif()
+
 #############################################################################
 # find how to link to the standard libraries                                #
 #############################################################################
@@ -118,15 +145,6 @@ endif()
 
 set(EIGEN_TEST_MAX_SIZE "320" CACHE STRING "Maximal matrix/vector size, default is 320")
 
-macro(ei_add_cxx_compiler_flag FLAG)
-  string(REGEX REPLACE "-" "" SFLAG1 ${FLAG})
-  string(REGEX REPLACE "\\+" "p" SFLAG ${SFLAG1})
-  check_cxx_compiler_flag(${FLAG} COMPILER_SUPPORT_${SFLAG})
-  if(COMPILER_SUPPORT_${SFLAG})
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${FLAG}")
-  endif()
-endmacro(ei_add_cxx_compiler_flag)
-
 if(NOT MSVC)
   # We assume that other compilers are partly compatible with GNUCC
 
@@ -362,8 +380,6 @@ if(EIGEN_TEST_NO_EXCEPTIONS)
   message(STATUS "Disabling exceptions in tests/examples")
 endif()
 
-option(EIGEN_TEST_CXX11 "Enable testing with C++11 and C++11 features (e.g. Tensor module)." OFF)
-
 set(EIGEN_CUDA_COMPUTE_ARCH 30 CACHE STRING "The CUDA compute architecture level to target when compiling CUDA code")
 
 include_directories(${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_BINARY_DIR})
diff --git a/cmake/EigenConfigureTesting.cmake b/cmake/EigenConfigureTesting.cmake
index af04709bd..3a824397f 100644
--- a/cmake/EigenConfigureTesting.cmake
+++ b/cmake/EigenConfigureTesting.cmake
@@ -56,8 +56,3 @@ elseif(MSVC)
 endif(CMAKE_COMPILER_IS_GNUCXX)
 
 
-check_cxx_compiler_flag("-std=c++11" EIGEN_COMPILER_SUPPORT_CXX11)
-
-if(EIGEN_TEST_CXX11 AND EIGEN_COMPILER_SUPPORT_CXX11)
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-endif()
diff --git a/doc/special_examples/CMakeLists.txt b/doc/special_examples/CMakeLists.txt
index 101fbc5f9..66ba4deee 100644
--- a/doc/special_examples/CMakeLists.txt
+++ b/doc/special_examples/CMakeLists.txt
@@ -19,7 +19,6 @@ if(QT4_FOUND)
   add_dependencies(all_examples Tutorial_sparse_example)
 endif(QT4_FOUND)
 
-check_cxx_compiler_flag("-std=c++11" EIGEN_COMPILER_SUPPORT_CPP11)
 if(EIGEN_COMPILER_SUPPORT_CPP11)
   add_executable(random_cpp11 random_cpp11.cpp)
   target_link_libraries(random_cpp11 ${EIGEN_STANDARD_LIBRARIES_TO_LINK_TO})
diff --git a/unsupported/test/CMakeLists.txt b/unsupported/test/CMakeLists.txt
index 80cccd828..3a8775a1c 100644
--- a/unsupported/test/CMakeLists.txt
+++ b/unsupported/test/CMakeLists.txt
@@ -68,7 +68,7 @@ ei_add_test(EulerAngles)
 
 find_package(MPFR 2.3.0)
 find_package(GMP)
-if(MPFR_FOUND AND EIGEN_COMPILER_SUPPORT_CXX11)
+if(MPFR_FOUND AND EIGEN_COMPILER_SUPPORT_CPP11)
   include_directories(${MPFR_INCLUDES} ./mpreal)
   ei_add_property(EIGEN_TESTED_BACKENDS "MPFR C++, ")
   set(EIGEN_MPFR_TEST_LIBRARIES ${MPFR_LIBRARIES} ${GMP_LIBRARIES})
@@ -154,7 +154,8 @@ if(EIGEN_TEST_CXX11)
   endif(EIGEN_TEST_SYCL)
   # It should be safe to always run these tests as there is some fallback code for
   # older compiler that don't support cxx11.
-  set(CMAKE_CXX_STANDARD 11)
+  # This is already set if EIGEN_TEST_CXX11 is enabled:
+  # set(CMAKE_CXX_STANDARD 11)
 
   ei_add_test(cxx11_eventcount "-pthread" "${CMAKE_THREAD_LIBS_INIT}")
   ei_add_test(cxx11_runqueue "-pthread" "${CMAKE_THREAD_LIBS_INIT}")