From 40fa6f98bf120b302c32be3fa15d7abbce4c96a7 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: bug #1606: Explicitly set the standard before
 find_package(StandardMathLibrary). Also replace EIGEN_COMPILER_SUPPORT_CXX11
 in favor of EIGEN_COMPILER_SUPPORT_CPP11. Grafted manually from
 a4afa90d161faab385a77f0e2764fb13ff3b9484

---
 CMakeLists.txt                    | 38 +++++++++++++++++++++++++++-----------
 cmake/EigenConfigureTesting.cmake |  5 -----
 unsupported/test/CMakeLists.txt   |  7 ++++---
 3 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6d74709a3..1d0f56367 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -68,6 +68,33 @@ 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                                #
 #############################################################################
@@ -119,15 +146,6 @@ 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
 
@@ -374,8 +392,6 @@ 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})
diff --git a/cmake/EigenConfigureTesting.cmake b/cmake/EigenConfigureTesting.cmake
index ba88228a0..1e72d92e9 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/unsupported/test/CMakeLists.txt b/unsupported/test/CMakeLists.txt
index 875842272..cda658e0e 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})
@@ -151,8 +151,9 @@ if(EIGEN_TEST_CXX11)
     else(EIGEN_SYCL_TRISYCL)
       # 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)
-      set(STD_CXX_FLAG "-std=c++11")
+      # This is already set if EIGEN_TEST_CXX11 is enabled:
+      # set(CMAKE_CXX_STANDARD 11)
+      # set(STD_CXX_FLAG "-std=c++11")
     endif(EIGEN_SYCL_TRISYCL)
 
     ei_add_test_sycl(cxx11_tensor_sycl ${STD_CXX_FLAG})
-- 
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