Merge pull request #1915 from akohlmey/cpp-11-cmake-3.10

Require C++11 and CMake 3.10

cmake/CMakeLists.txt

@@ -2,7 +2,7 @@
 # CMake build system
 # This file is part of LAMMPS
 # Created by Christoph Junghans and Richard Berger
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.10)
 
 project(lammps CXX)
 set(SOVERSION 0)
@@ -55,12 +55,9 @@ if(${CMAKE_CXX_COMPILER_ID} STREQUAL "Intel")
   set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -restrict -std=c++11")
 endif()
 
-option(DISABLE_CXX11_REQUIREMENT "Disable check that requires C++11 for compiling LAMMPS" OFF)
+# we require C++11
-if(DISABLE_CXX11_REQUIREMENT)
+set(CMAKE_CXX_STANDARD 11)
-  add_definitions(-DLAMMPS_CXX98)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
-# else()
-#  set(CMAKE_CXX_STANDARD 11)
-endif()
 
 # GNU compiler features
 if (${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU")
@@ -355,9 +352,6 @@ endforeach(HEADER)
 set(MATH_LIBRARIES "m" CACHE STRING "math library")
 mark_as_advanced( MATH_LIBRARIES )
 include(CheckLibraryExists)
-if (CMAKE_VERSION VERSION_LESS "3.4")
-  enable_language(C) # check_library_exists isn't supported without a C compiler before v3.4
-endif()
 # RB: disabled this check because it breaks with KOKKOS CUDA enabled
 #foreach(FUNC sin cos)
 #  check_library_exists(${MATH_LIBRARIES} ${FUNC} "" FOUND_${FUNC}_${MATH_LIBRARIES})

cmake/Modules/Packages/GPU.cmake

@@ -1,7 +1,4 @@
 if(PKG_GPU)
-    if (CMAKE_VERSION VERSION_LESS "3.1")
-      message(FATAL_ERROR "For the GPU package you need at least cmake-3.1")
-    endif()
     set(GPU_SOURCES_DIR ${LAMMPS_SOURCE_DIR}/GPU)
     set(GPU_SOURCES ${GPU_SOURCES_DIR}/gpu_extra.h
                     ${GPU_SOURCES_DIR}/fix_gpu.h

cmake/Modules/Packages/LATTE.cmake

@@ -8,9 +8,6 @@ if(PKG_LATTE)
   endif()
   option(DOWNLOAD_LATTE "Download the LATTE library instead of using an already installed one" ${DOWNLOAD_LATTE_DEFAULT})
   if(DOWNLOAD_LATTE)
-    if (CMAKE_VERSION VERSION_LESS "3.7") # due to SOURCE_SUBDIR
-      message(FATAL_ERROR "For downlading LATTE you need at least cmake-3.7")
-    endif()
     if(CMAKE_GENERATOR STREQUAL "Ninja")
       message(FATAL_ERROR "Cannot build downloaded LATTE library with Ninja build tool")
     endif()

cmake/Modules/Packages/MSCG.cmake

@@ -8,9 +8,6 @@ if(PKG_MSCG)
   endif()
   option(DOWNLOAD_MSCG "Download MSCG library instead of using an already installed one)" ${DOWNLOAD_MSCG_DEFAULT})
   if(DOWNLOAD_MSCG)
-    if (CMAKE_VERSION VERSION_LESS "3.7") # due to SOURCE_SUBDIR
-      message(FATAL_ERROR "For downlading MSCG you need at least cmake-3.7")
-    endif()
     if(CMAKE_GENERATOR STREQUAL "Ninja")
       message(FATAL_ERROR "Cannot build downloaded MSCG library with Ninja build tool")
     endif()

cmake/Modules/Packages/USER-MOLFILE.cmake

@@ -1,8 +1,4 @@
 if(PKG_USER-MOLFILE)
-  if (CMAKE_VERSION VERSION_LESS "3.10") # due to INTERFACE without a library
-    message(FATAL_ERROR "For configuring USER-MOLFILE you need CMake 3.10 or later")
-  endif()
-
   set(MOLFILE_INCLUDE_DIRS "${LAMMPS_LIB_SOURCE_DIR}/molfile" CACHE STRING "Path to VMD molfile plugin headers")
   add_library(molfile INTERFACE)
   target_include_directories(molfile INTERFACE ${MOLFILE_INCLUDE_DIRS})

doc/src/Build_cmake.rst

@@ -95,10 +95,8 @@ this directory or sub-directories within it that CMake creates.
    directory to un-install all packages.  The purge removes all the \*.h
    files auto-generated by make.
 
-You must have CMake version 2.8 or later on your system to build
+You must have CMake version 3.10 or later on your system to build
-LAMMPS.  A handful of LAMMPS packages (KOKKOS, LATTE, MSCG) require a
+LAMMPS.  Installation instructions for CMake are below.
-later version.  CMake will print a message telling you if a later
-version is required.  Installation instructions for CMake are below.
 
 After the initial build, if you edit LAMMPS source files, or add your
 own new files to the source directory, you can just re-type make from

doc/src/Build_settings.rst

@@ -23,11 +23,11 @@ explain how to do this for building both with CMake and make.
 C++11 standard compliance
 ------------------------------------------
 
-The LAMMPS developers plan to transition to make the C++11 standard the
+A C++11 standard compatible compiler is a requirement for compiling LAMMPS.
-minimum requirement for compiling LAMMPS.  Currently this only applies to
+LAMMPS version 3 March 2020 is the last version compatible with the previous
-some packages like KOKKOS while the rest aims to be compatible with the C++98
+C++98 standard for the core code and most packages. Most currently used
-standard.  Most currently used compilers are compatible with C++11; some need
+C++ compilers are compatible with C++11, but some older ones may need extra
-to set extra flags to enable C++11 compliance.  Example for GNU c++:
+flags to enable C++11 compliance.  Example for GNU c++ 4.8.x:
 
 .. code-block:: make
 

src/lmptype.h

@@ -28,6 +28,12 @@
 #ifndef LMP_LMPTYPE_H
 #define LMP_LMPTYPE_H
 
+// C++11 check
+
+#if __cplusplus < 201103L
+#error LAMMPS requires a C++11 (or later) compliant compiler. Enable C++11 compatibility or upgrade the compiler.
+#endif
+
 #ifndef __STDC_LIMIT_MACROS
 #define __STDC_LIMIT_MACROS
 #endif
@@ -38,8 +44,8 @@
 
 #include <climits>
 #include <cstdlib>
-#include <stdint.h>   // <cstdint> requires C++-11
+#include <cstdint>
-#include <inttypes.h> // <cinttypes> requires C++-11
+#include <cinttypes>
 
 // grrr - IBM Power6 does not provide this def in their system header files