From 8d001c0f6aee7e9cc4dd1f39d3f327db22f8a370 Mon Sep 17 00:00:00 2001
From: Martin Quinson <martin.quinson@loria.fr>
Date: Sat, 25 Jul 2015 11:28:16 +0200
Subject: [PATCH] CMake cleanups: move the C/C++ std detection to the right
 place; add doc

---
 CMakeLists.txt               | 48 +++++++++++++++++++++++++++++++++---
 buildtools/Cmake/Flags.cmake | 47 ++++++-----------------------------
 2 files changed, 53 insertions(+), 42 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f8fc1825f7..e280cd8a12 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,20 +1,57 @@
 cmake_minimum_required(VERSION 2.6)
+
 ### Need to set rc ccompiler before enable language
 if(WIN32)
   SET(CMAKE_RC_COMPILER "windres")
 endif()
 project(SimGrid C)
 
+## 
+## Check the C/C++ standard that we need
+##   See also buildtools/Cmake/Flags.cmake that sets our paranoid warning flags
+
 enable_language(CXX)
 
 INCLUDE(CheckCCompilerFlag)
 CHECK_C_COMPILER_FLAG(-fstack-cleaner HAVE_C_STACK_CLEANER)
 
-if (APPLE)
-  set(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
-  set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
+## Request full debugging flags
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g3")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g3")
+set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -g")
+
+## We need a decent support of the c++11 standard
+include(CheckCXXCompilerFlag)
+CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
+if(COMPILER_SUPPORTS_CXX11)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+else()
+  message(FATAL_ERROR 
+          "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. "
+	  "Please use a decent C++ compiler.")
+endif()
+if (CMAKE_COMPILER_IS_GNUCC)
+  if (COMPILER_CXX_VERSION_MAJOR_MINOR STRLESS "4.7")
+    message(FATAL_ERROR
+            "SimGrid needs g++ version 4.7 to compile "
+	    "(c++11 support of previous versions is too limited).")
+  endif()
 endif()
 
+### And we need C11 standard, too
+include(CheckCCompilerFlag)
+CHECK_C_COMPILER_FLAG("-std=gnu11" COMPILER_SUPPORTS_C11)
+if(COMPILER_SUPPORTS_C11)
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu11")
+else()
+  message(FATAL_ERROR 
+          "The compiler ${CMAKE_C_COMPILER} has no C11 support. "
+	  "Please use a decent C compiler "
+	  "(note that c++11 support of ${CMAKE_CXX_COMPILER} seems ok).")
+endif()
+
+
+### SMPI vs. Fortran
 if ((NOT DEFINED enable_smpi OR enable_smpi) AND NOT APPLE) # smpi is enabled by default
   # Call enable_language(Fortran) in order to load the build rules for
   # this language, needed by teshsuite/smpi/mpich-test/.  Use
@@ -121,6 +158,11 @@ if(NOT PERL_EXECUTABLE)
   message(FATAL_ERROR "-- SimGrid cannot be compiled without Perl installed -- sorry. Bailling out.")
 endif()
 
+if (APPLE)
+  set(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
+  set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
+endif()
+
 ### Set some variables for Cmake
 SET(LIBRARY_OUTPUT_PATH ${CMAKE_BINARY_DIR}/lib)
 
diff --git a/buildtools/Cmake/Flags.cmake b/buildtools/Cmake/Flags.cmake
index b3dc83771c..dcf37d85ee 100644
--- a/buildtools/Cmake/Flags.cmake
+++ b/buildtools/Cmake/Flags.cmake
@@ -1,46 +1,15 @@
-set(warnCFLAGS "")
-set(optCFLAGS "")
-
 ##
-## Request full debugging flags
+## This file is in charge of setting our paranoid flags with regard to warnings and optimization.
 ##
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g3")
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g3")
-set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -g")
+##   These flags do break some classical CMake tests, so you don't
+##   want to do so before the very end of the configuration.
+## 
+##   Other compiler flags (C/C++ standard version) are tested and set
+##   by the beginning of the configuration, directly in ~/CMakeList.txt
 
-##
-## We need a decent support of the c++11 standard
-##
-include(CheckCXXCompilerFlag)
-CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
-if(COMPILER_SUPPORTS_CXX11)
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-else()
-  message(FATAL_ERROR 
-          "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. "
-	  "Please use a decent C++ compiler.")
-endif()
-if (CMAKE_COMPILER_IS_GNUCC)
-  if (COMPILER_CXX_VERSION_MAJOR_MINOR STRLESS "4.7")
-    message(FATAL_ERROR
-            "SimGrid needs g++ version 4.7 to compile "
-	    "(c++11 support of previous versions is too limited).")
-  endif()
-endif()
+set(warnCFLAGS "")
+set(optCFLAGS "")
 
-###
-### And we need C11 standard, too
-###
-include(CheckCCompilerFlag)
-CHECK_C_COMPILER_FLAG("-std=gnu11" COMPILER_SUPPORTS_C11)
-if(COMPILER_SUPPORTS_C11)
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu11")
-else()
-  message(FATAL_ERROR 
-          "The compiler ${CMAKE_C_COMPILER} has no C11 support. "
-	  "Please use a decent C compiler "
-	  "(note that c++11 support of ${CMAKE_CXX_COMPILER} seems ok).")
-endif()
 
 
 if(enable_compile_warnings)
-- 
2.20.1