add preliminary support for compiling/loading plugins on windows

doc/src/plugin.rst

@@ -58,6 +58,9 @@ Restrictions
 
 Plugins are currently not available on Windows.
 
+For the loading of plugins to work, the LAMMPS library must be
+:ref:`compiled as a shared library <library>`.
+
 Plugins are dependent on the LAMMPS binary interface (ABI)
 and particularly the MPI library used. So they are not guaranteed
 to work when the plugin was compiled with a different MPI library

examples/plugins/CMakeLists.txt

@@ -31,11 +31,6 @@ endif()
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
-# bail out on windows
-if(CMAKE_SYSTEM_NAME STREQUAL Windows)
-  message(FATAL_ERROR "LAMMPS plugins are currently not supported on Windows")
-endif()
-
 set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR})
 include(CheckIncludeFileCXX)
 include(LAMMPSInterfaceCXX)
@@ -53,12 +48,13 @@ target_link_libraries(nve2plugin PRIVATE lammps)
 add_library(helloplugin MODULE helloplugin.cpp)
 target_link_libraries(helloplugin PRIVATE lammps)
 
-set_target_properties(morse2plugin nve2plugin helloplugin PROPERTIES
-                      PREFIX ""
-                      LINK_FLAGS "-rdynamic")
+set_target_properties(morse2plugin nve2plugin helloplugin PROPERTIES PREFIX "")
 
-# MacOS seems to need this
 if(CMAKE_SYSTEM_NAME STREQUAL Darwin)
   set_target_properties(morse2plugin nve2plugin helloplugin PROPERTIES
                         LINK_FLAGS "-Wl,-undefined,dynamic_lookup")
+elseif(CMAKE_SYSTEM_NAME STREQUAL Windows)
+  set_target_properties(morse2plugin nve2plugin helloplugin PROPERTIES LINK_FLAGS "-Wl,--undefined")
+else()
+  set_target_properties(morse2plugin nve2plugin helloplugin PROPERTIES LINK_FLAGS "-rdynamic")
 endif()

examples/plugins/Makefile.serial

@@ -0,0 +1,30 @@
+CXX=g++
+CXXFLAGS=-I../../src -I../../src/STUBS -Wall -Wextra -O3 -fPIC -I../../src/USER-OMP -fopenmp
+LD=$(CXX) -shared -rdynamic -fopenmp
+
+default: morse2plugin.so nve2plugin.so helloplugin.so
+
+helloplugin.so: helloplugin.o
+	$(LD) -o $@ $^
+
+morse2plugin.so: morse2plugin.o pair_morse2.o pair_morse2_omp.o
+	$(LD) -o $@ $^
+
+nve2plugin.so: nve2plugin.o fix_nve2.o
+	$(LD) -o $@ $^
+
+.cpp.o:
+	$(CXX) -o $@ $(CXXFLAGS) -c $<
+
+helloplugin.o: helloplugin.cpp
+
+pair_morse2.o: pair_morse2.cpp pair_morse2.h
+pair_morse2_omp.o: pair_morse2_omp.cpp pair_morse2_omp.h pair_morse2.h
+morse2plugin.o: morse2plugin.cpp pair_morse2.h pair_morse2_omp.h
+
+fix_nve2.o: fix_nve2.cpp fix_nve2.h
+nve2plugin.o: nve2plugin.cpp fix_nve2.h
+
+clean:
+	rm -rf *~ *.so *.dylib *.o log.lammps CMakeCache.txt CMakeFiles
+

src/MAKE/Makefile.mpi

@@ -18,7 +18,7 @@ SIZE =		size
 
 ARCHIVE =	ar
 ARFLAGS =	-rc
-SHLIBFLAGS =	-shared
+SHLIBFLAGS =	-shared -rdynamic
 
 # ---------------------------------------------------------------------
 # LAMMPS-specific settings, all OPTIONAL

src/MAKE/Makefile.serial

@@ -18,7 +18,7 @@ SIZE =		size
 
 ARCHIVE =	ar
 ARFLAGS =	-rc
-SHLIBFLAGS =	-shared
+SHLIBFLAGS =	-shared -rdynamic
 
 # ---------------------------------------------------------------------
 # LAMMPS-specific settings, all OPTIONAL

src/plugin.cpp

@@ -24,12 +24,49 @@
 #include <map>
 #include <list>
 
-#ifdef _WIN32
+#if defined(_WIN32)
 #include <windows.h>
 #else
 #include <dlfcn.h>
 #endif
 
+#if defined(_WIN32)
+
+// open a shared object file
+static void *my_dlopen(const char *fname) {
+  return (void *)LoadLibrary(fname);
+}
+
+// resolve a symbol in shared object
+static void *my_dlsym(void *h, const char *sym) {
+  return (void *)GetProcAddress((HINSTANCE)h, sym);
+}
+
+// close a shared object
+static int my_dlclose(void *h) {
+  /* FreeLibrary returns nonzero on success */
+  return !FreeLibrary((HINSTANCE)h);
+}
+
+#else
+
+// open a shared object file
+static void *my_dlopen(const char *fname) {
+  return dlopen(fname, RTLD_NOW|RTLD_GLOBAL);
+}
+
+// resolve a symbol in shared object
+static void *my_dlsym(void *h, const char *sym) {
+  return dlsym(h, sym);
+}
+
+// close a shared object
+static int my_dlclose(void *h) {
+  return dlclose(h);
+}
+
+#endif
+
 namespace LAMMPS_NS
 {
   // list of plugin information data for loaded styles
@@ -42,13 +79,11 @@ namespace LAMMPS_NS
   void plugin_load(const char *file, LAMMPS *lmp)
   {
     int me = lmp->comm->me;
-#if defined(WIN32)
-    lmp->error->all(FLERR,"Loading of plugins on Windows not yet supported\n");
-#else
 
     // open DSO file from given path; load symbols globally
-
-    void *dso = dlopen(file,RTLD_NOW|RTLD_GLOBAL);
+    
+    void *dso = my_dlopen(file);
+    
     if (dso == nullptr) {
       if (me == 0)
         utils::logmesg(lmp,fmt::format("Open of file {} failed\n",file));
@@ -58,9 +93,10 @@ namespace LAMMPS_NS
     // look up lammpsplugin_init() function in DSO
     // function must have C bindings so there is no name mangling
 
-    void *initfunc = dlsym(dso,"lammpsplugin_init");
+    void *initfunc = my_dlsym(dso,"lammpsplugin_init");
+
     if (initfunc == nullptr) {
-      dlclose(dso);
+      my_dlclose(dso);
 
       if (me == 0)
         utils::logmesg(lmp,fmt::format("Plugin symbol lookup failure in "
@@ -74,7 +110,6 @@ namespace LAMMPS_NS
 
     (*(lammpsplugin_initfunc)(initfunc))((void *)lmp, dso,
                                          (void *)&plugin_register);
-#endif
   }
 
   /* --------------------------------------------------------------------
@@ -221,11 +256,7 @@ namespace LAMMPS_NS
     // if reference count is down to zero, close DSO handle.
 
     -- dso_refcounter[handle];
-    if (dso_refcounter[handle] == 0) {
-#ifndef WIN32
-      dlclose(handle);
-#endif
-    }
+    if (dso_refcounter[handle] == 0) my_dlclose(handle);
   }
 
   /* --------------------------------------------------------------------