Merge pull request #4344 from lammps/cmake-cpp-std-deprecation

Prepare development branch for requiring C++17 and deprecating GNU make support for some packages

cmake/CMakeLists.txt

@@ -3,6 +3,9 @@
 # CMake build system
 # This file is part of LAMMPS
 cmake_minimum_required(VERSION 3.16)
+if(CMAKE_VERSION VERSION_LESS 3.20)
+  message(WARNING "LAMMPS is planning to require at least CMake version 3.20 by Summer 2025. Please upgrade!")
+endif()
 ########################################
 # set policy to silence warnings about ignoring <PackageName>_ROOT but use it
 if(POLICY CMP0074)
@@ -144,16 +147,28 @@ if((PKG_KOKKOS) AND (Kokkos_ENABLE_CUDA) AND NOT (CMAKE_CXX_COMPILER_ID STREQUAL
   set(CMAKE_TUNE_DEFAULT "${CMAKE_TUNE_DEFAULT}" "-Xcudafe --diag_suppress=unrecognized_pragma,--diag_suppress=128")
 endif()
 
-# we require C++11 without extensions. Kokkos requires at least C++17 (currently)
+# we *require* C++11 without extensions but prefer C++17.
+# Kokkos requires at least C++17 (currently)
 if(NOT CMAKE_CXX_STANDARD)
+  if(cxx_std_17 IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+    set(CMAKE_CXX_STANDARD 17)
+  else()
     set(CMAKE_CXX_STANDARD 11)
   endif()
+endif()
 if(CMAKE_CXX_STANDARD LESS 11)
   message(FATAL_ERROR "C++ standard must be set to at least 11")
 endif()
+if(CMAKE_CXX_STANDARD LESS 17)
+  message(WARNING "Selecting C++17 standard is preferred over C++${CMAKE_CXX_STANDARD}")
+endif()
 if(PKG_KOKKOS AND (CMAKE_CXX_STANDARD LESS 17))
   set(CMAKE_CXX_STANDARD 17)
 endif()
+# turn off C++17 check in lmptype.h
+if(LAMMPS_CXX11)
+  add_compile_definitions(LAMMPS_CXX11)
+endif()
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF CACHE BOOL "Use compiler extensions")
 # ugly hacks for MSVC which by default always reports an old C++ standard in the __cplusplus macro
@@ -347,6 +362,17 @@ foreach(PKG ${STANDARD_PACKAGES} ${SUFFIX_PACKAGES})
   option(PKG_${PKG} "Build ${PKG} Package" OFF)
 endforeach()
 
+set(DEPRECATED_PACKAGES AWPMD ATC POEMS)
+foreach(PKG ${DEPRECATED_PACKAGES})
+  if(PKG_${PKG})
+    message(WARNING
+          "The ${PKG} package will be removed from LAMMPS in Summer 2025 due to lack of "
+          "maintenance and use of code constructs that conflict with modern C++ compilers "
+          "and standards.  Please contact developers@lammps.org if you have any concerns "
+          "about this step.")
+  endif()
+endforeach()
+
 ######################################################
 # packages with special compiler needs or external libs
 ######################################################

doc/src/Build.rst

@@ -1,10 +1,14 @@
 Build LAMMPS
 ============
 
-LAMMPS is built as a library and an executable from source code using
+LAMMPS is built as a library and an executable from source code using a
-either traditional makefiles for use with GNU make (which may require
+build environment generated by CMake (Unix Makefiles, Ninja, Xcode,
-manual editing), or using a build environment generated by CMake (Unix
+Visual Studio, KDevelop, CodeBlocks and more depending on the platform).
-Makefiles, Ninja, Xcode, Visual Studio, KDevelop, CodeBlocks and more).
+Using CMake is the preferred way to build LAMMPS.  In addition, LAMMPS
+can be compiled using the legacy build system based on traditional
+makefiles for use with GNU make (which may require manual editing).
+Support for the legacy build system is slowly being phased out and may
+not be available for all optional features.
 
 As an alternative, you can download a package with pre-built executables
 or automated build trees, as described in the :doc:`Install <Install>`

doc/src/Build_cmake.rst

@@ -16,7 +16,7 @@ environments is on a :doc:`separate page <Howto_cmake>`.
 
 .. note::
 
-   LAMMPS currently requires that CMake version 3.16 or later is available.
+   LAMMPS currently requires that CMake version 3.20 or later is available.
 
 .. warning::
 
@@ -32,11 +32,11 @@ environments is on a :doc:`separate page <Howto_cmake>`.
 Advantages of using CMake
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 
-CMake is an alternative to compiling LAMMPS in the traditional way
+CMake is the preferred way of compiling LAMMPS in contrast to the legacy
-through :doc:`(manually customized) makefiles <Build_make>`.  Using
+build system based on GNU make and through :doc:`(manually customized)
-CMake has multiple advantages that are specifically helpful for
+makefiles <Build_make>`.  Using CMake has multiple advantages that are
-people with limited experience in compiling software or for people
+specifically helpful for people with limited experience in compiling
-that want to modify or extend LAMMPS.
+software or for people that want to modify or extend LAMMPS.
 
 - CMake can detect available hardware, tools, features, and libraries
   and adapt the LAMMPS default build configuration accordingly.

doc/src/Build_make.rst

@@ -8,6 +8,10 @@ Building LAMMPS with traditional makefiles requires that you have a
 for customizing your LAMMPS build with a number of global compilation
 options and features.
 
+This build system is slowly being phased out and may not support all
+optional features and packages in LAMMPS.  It is recommended to switch
+to the :doc:`CMake based build system <Build_cmake>`.
+
 Requirements
 ^^^^^^^^^^^^
 

doc/src/Modify_requirements.rst

@@ -208,20 +208,21 @@ Build system (strict)
 
 LAMMPS currently supports two build systems: one that is based on
 :doc:`traditional Makefiles <Build_make>` and one that is based on
-:doc:`CMake <Build_cmake>`.  Therefore, your contribution must be
+:doc:`CMake <Build_cmake>`.  As of fall 2024, it is no longer required
-compatible with and support both build systems.
+to support the traditional make build system.  New packages may choose
+to only support building with CMake.  Additions to existing packages
+must follow the requirements set by that package.
 
 For a single pair of header and implementation files that are an
 independent feature, it is usually only required to add them to
 ``src/.gitignore``.
 
 For traditional make, if your contributed files or package depend on
-other LAMMPS style files or packages also being installed
+other LAMMPS style files or packages also being installed (e.g. because
-(e.g. because your file is a derived class from the other LAMMPS
+your file is a derived class from the other LAMMPS class), then an
-class), then an ``Install.sh`` file is also needed to check for those
+``Install.sh`` file is also needed to check for those dependencies and
-dependencies and modifications to ``src/Depend.sh`` to trigger the checks.
+modifications to ``src/Depend.sh`` to trigger the checks.  See other
-See other README and Install.sh files in other directories as
+README and Install.sh files in other directories as examples.
-examples.
 
 Similarly, for CMake support, changes may need to be made to
 ``cmake/CMakeLists.txt``, some of the files in ``cmake/presets``, and

python/lammps/pylammps.py

@@ -449,12 +449,6 @@ class PyLammps(object):
   """
 
   def __init__(self, name="", cmdargs=None, ptr=None, comm=None, verbose=False):
-    print("WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING")
-    print()
-    print("The PyLammps interface is deprecated and will be removed in future versions.")
-    print("Please use the lammps Python class instead.")
-    print()
-    print("WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING")
     self.has_echo = False
     self.verbose = verbose
 
@@ -476,6 +470,12 @@ class PyLammps(object):
     self.comm_nprocs = self.lmp.extract_setting("world_size")
     self.comm_me = self.lmp.extract_setting("world_rank")
     if self.comm_me == 0:
+      print("\nWARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING")
+      print("WARNING:")
+      print("WARNING:   The PyLammps class is obsolete and will be removed from LAMMPS soon.")
+      print("WARNING:   Please use the lammps Python class instead.")
+      print("WARNING:")
+      print("WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING\n")
       print("LAMMPS output is captured by PyLammps wrapper")
       if self.comm_nprocs > 1:
         print("WARNING: Using PyLammps with multiple MPI ranks is experimental. Not all functionality is supported.")

src/ATC/Install.sh

@@ -9,6 +9,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+ The ATC package will be removed from LAMMPS in Summer 2025 due to lack of
+ maintenance and use of code constructs that conflict with modern C++ compilers
+ and standards.  Please contact developers@lammps.org if you have any concerns
+ about this step.
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 action () {
   if (test $mode = 0) then
     rm -f ../$1

src/AWPMD/Install.sh

@@ -9,6 +9,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+ The AWPMD package will be removed from LAMMPS in Summer 2025 due to lack of
+ maintenance and use of code constructs that conflict with modern C++ compilers
+ and standards.  Please contact developers@lammps.org if you have any concerns
+ about this step.
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 action () {
   if (test $mode = 0) then
     rm -f ../$1

src/COLVARS/Install.sh

@@ -9,6 +9,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+  Support for building the COLVARS package with the legacy build system using GNU
+  make will be removed in Summer 2025.  Please switch to using CMake to build
+  LAMMPS as soon as possible and report any problems to developers@lammps.org
+  or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 action () {
   if (test $mode = 0) then
     rm -f ../$1

src/COMPRESS/Install.sh

@@ -7,6 +7,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+ Support for building the COMPRESS package with the legacy build system using
+ GNU make will be removed in Summer 2025.  Please switch to using CMake to build
+ LAMMPS as soon as possible and report any problems to developers@lammps.org
+ or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 # arg1 = file, arg2 = file it depends on
 
 action () {

src/ELECTRODE/Install.sh

@@ -11,6 +11,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+  Support for building the ELECTRODE package with the legacy build system using
+  GNU make will be removed in Summer 2025.  Please switch to using CMake to build
+  LAMMPS as soon as possible and report any problems to developers@lammps.org
+  or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 # arg1 = file, arg2 = file it depends on
 
 action () {

src/GPU/Install.sh

@@ -7,6 +7,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+  Support for building the GPU package with the legacy build system using GNU
+  make will be removed in Summer 2025.  Please switch to using CMake to build
+  LAMMPS as soon as possible and report any problems to developers@lammps.org
+  or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 # arg1 = file, arg2 = file it depends on
 
 action () {

src/KOKKOS/Install.sh

@@ -7,6 +7,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+  Support for building the KOKKOS package with the legacy build system using GNU
+  make will be removed in Summer 2025.  Please switch to using CMake to build
+  LAMMPS as soon as possible and report any problems to developers@lammps.org
+  or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 # arg1 = file, arg2 = file it depends on
 
 action () {

src/LEPTON/Install.sh

@@ -9,6 +9,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+  Support for building the LEPTON package with the legacy build system using GNU
+  make will be removed in Summer 2025.  Please switch to using CMake to build
+  LAMMPS as soon as possible and report any problems to developers@lammps.org
+  or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 action () {
   if (test $mode = 0) then
     rm -f ../$1

src/MAKE/Makefile.mpi

@@ -7,12 +7,12 @@ SHELL = /bin/sh
 # specify flags and libraries needed for your compiler
 
 CC =		mpicxx
-CCFLAGS =	-g -O3 -std=c++11
+CCFLAGS =	-g -O3 # -std=c++17
 SHFLAGS =	-fPIC
 DEPFLAGS =	-M
 
 LINK =		mpicxx
-LINKFLAGS =	-g -O3 -std=c++11
+LINKFLAGS =	-g -O3 # -std=c++17
 LIB =
 SIZE =		size
 
@@ -28,7 +28,7 @@ SHLIBFLAGS =	-shared -rdynamic
 # LAMMPS ifdef settings
 # see possible settings in Section 3.5 of the manual
 
-LMP_INC =	-DLAMMPS_GZIP -DLAMMPS_MEMALIGN=64  # -DLAMMPS_CXX98
+LMP_INC =	-DLAMMPS_GZIP -DLAMMPS_MEMALIGN=64  # -DLAMMPS_CXX11
 
 # MPI library
 # see discussion in Section 3.4 of the manual

src/MAKE/Makefile.serial

@@ -7,12 +7,12 @@ SHELL = /bin/sh
 # specify flags and libraries needed for your compiler
 
 CC =		g++
-CCFLAGS =	-g -O3 -std=c++11
+CCFLAGS =	-g -O3 # -std=c++17
 SHFLAGS =	-fPIC
 DEPFLAGS =	-M
 
 LINK =		g++
-LINKFLAGS =	-g -O -std=c++11
+LINKFLAGS =	-g -O # -std=c++17
 LIB =
 SIZE =		size
 
@@ -28,7 +28,7 @@ SHLIBFLAGS =	-shared -rdynamic
 # LAMMPS ifdef settings
 # see possible settings in Section 3.5 of the manual
 
-LMP_INC =	-DLAMMPS_GZIP -DLAMMPS_MEMALIGN=64  # -DLAMMPS_CXX98
+LMP_INC =	-DLAMMPS_GZIP -DLAMMPS_MEMALIGN=64  # -DLAMMPS_CXX11
 
 # MPI library
 # see discussion in Section 3.4 of the manual

src/ML-POD/Install.sh

@@ -7,6 +7,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+ Support for building the ML-POD package with the legacy build system using GNU
+ make will be removed in Summer 2025.  Please switch to using CMake to build
+ LAMMPS as soon as possible and report any problems to developers@lammps.org
+ or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 # arg1 = file, arg2 = file it depends on
 
 action () {

src/PLUMED/Install.sh

@@ -7,6 +7,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+  Support for building the PLUMED package with the legacy build system using GNU
+  make will be removed in Summer 2025.  Please switch to using CMake to build
+  LAMMPS as soon as possible and report any problems to developers@lammps.org
+  or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 # arg1 = file, arg2 = file it depends on
 
 action () {

src/POEMS/Install.sh

@@ -9,6 +9,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+ The POEMS package will be removed from LAMMPS in Summer 2025 due to lack of
+ maintenance and use of code constructs that conflict with modern C++ compilers
+ and standards.  Please contact developers@lammps.org if you have any concerns
+ about this step.
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 action () {
   if (test $mode = 0) then
     rm -f ../$1

src/VTK/Install.sh

@@ -7,6 +7,19 @@ mode=$1
 LC_ALL=C
 export LC_ALL
 
+cat <<EOF
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+
+  Support for building the VTK package with the legacy build system using GNU
+  make will be removed in Summer 2025.  Please switch to using CMake to build
+  LAMMPS as soon as possible and report any problems to developers@lammps.org
+  or post a bug report issue at https://github.com/lammps/lammps/issues
+
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING-WARNING
+EOF
+
 # arg1 = file, arg2 = file it depends on
 
 action () {

src/lmptype.h

@@ -34,6 +34,13 @@
 #error LAMMPS requires a C++11 (or later) compliant compiler. Enable C++11 compatibility or upgrade the compiler.
 #endif
 
+// C++17 check
+#ifndef LAMMPS_CXX11
+#if __cplusplus < 201703L
+#error LAMMPS is planning to transition to requiring C++17. To disable this error please use a C++17 compliant compiler, enable C++17 support, or define -DLAMMPS_CXX11 in your makefile or when running cmake
+#endif
+#endif
+
 #ifndef __STDC_LIMIT_MACROS
 #define __STDC_LIMIT_MACROS
 #endif