Add CMAKE variable to enable creation of static OpenMP libraries instead of dynamic ones

[jmellorcrummey]

Summary

When building executables for Cray supercomputers, statically-linked executables are preferred. This patch makes it possible to build the OpenMP runtime as an archive for building statically-linked executables.

The patch adds the flag LIBOMP_SHARED_LIBRARY, which defaults to true. When true, a build of the OpenMP runtime yields dynamic libraries. When false, a build of the OpenMP runtime yields static libraries. There is no setting that allows both kinds of libraries to be built.

[jlpeyton]

Add the new variable to Build_With_CMake.txt with note that it isn't available on Windows.

runtime/CMakeLists.txt

280–283

This is a minor nit, but can this be renamed to LIBOMP_STATIC_LIBRARY which is FALSE by default. Setting a feature to true to enable the feature seems a little more intuitive for the user. Also, make a note in the comment that this feature isn't available on Windows, and put below this:

if(WIN32 AND LIBOMP_STATIC_LIBRARY)
  libomp_error_say("Static libraries requested but not available on Windows")
endif()

[hfinkel]

runtime/CMakeLists.txt

280–283

This is a minor nit, but can this be renamed to LIBOMP_STATIC_LIBRARY which is FALSE by default.

FWIW, the libc++ option is named:

option(LIBCXX_ENABLE_SHARED "Build libc++ as a shared library." ON)

and the LLVM option is named (strangely without an LLVM_ prefix):

option(BUILD_SHARED_LIBS
  "Build all libraries as shared libraries instead of static" OFF)

so it might be more consistent to leave the option with the proposed sense. We might even want to mirror libc++ more closely and name it LIBOMP_ENABLE_SHARED.

I don't, however, feel strongly about it either way. I would like to get this in, however; it is something we need.

[jmellorcrummey]

Address Jonathan's comments:

• Renamed flag LIBOMP_SHARED_LIBRARY to LIBOMP_STATIC_LIBRARY.
• Add documentation for the flag to runtime/Build_With_CMake.txt

[jlpeyton]

runtime/CMakeLists.txt

280–283

Ok, I do think we should mimic libc++ to keep the interface similar. Sorry John, but can you change it to LIBOMP_ENABLE_SHARED which is on be default?

Just an FYI,
The BUILD_SHARED_LIBS variable is actually a standard CMake variable (with no CMAKE_ prefix).

[jmellorcrummey]

Update revision to meet Jonathan's requirement of the day: change control flag to LIBOMP_ENABLE_SHARED.

[jlpeyton]

Thanks. LGTM.

runtime/Build_With_CMake.txt

 
 -DLIBOMP_USE_VERSION_SYMBOLS=on|off
 Should versioned symbols be used for building the library?
 This option only makes sense for ELF based libraries where version
 symbols are supported (Linux, some BSD* variants).  It is off
 by default for Windows and Mac, but on for other Unix based operating
 systems.
 
+-DLIBOMP_STATIC_LIBRARY=off|on
+Static library instead of shared library? (Not supported on Windows)
+If DLIBOMP_STATIC_LIBRARY is on, then static OpenMP libraries will be 
+built instead of dynamic ones.
+
 -DLIBOMP_OMPT_SUPPORT=off|on
 Should OMPT support be included in the build? (Not supported on Windows)
 If LIBOMP_OMPT_SUPPORT is off, then both ompt_blame and ompt_trace are ignored.
 
 -DLIBOMP_OMPT_BLAME=on|off
 Should OMPT blame functionality be included in the build?
 
 -DLIBOMP_OMPT_TRACE=on|off

runtime/CMakeLists.txt

 if(LIBOMP_STATS AND (NOT LIBOMP_HAVE_STATS))
   libomp_error_say("Stats-gathering functionality requested but not available")
 endif()
 # The stats functionality requires the std c++ library
 if(LIBOMP_STATS)
   set(LIBOMP_USE_STDCPPLIB TRUE)
 endif()
 
+# Shared library can be switched to a static library
+set(LIBOMP_STATIC_LIBRARY FALSE CACHE BOOL
+  "Static library instead of shared library?")
+
+if(WIN32 AND LIBOMP_STATIC_LIBRARY)
+  libomp_error_say("Static libraries requested but not available on Windows")
+endif()
+
 # OMPT-support
 set(LIBOMP_OMPT_DEBUG FALSE CACHE BOOL
   "Trace OMPT initialization?")
 set(LIBOMP_OMPT_SUPPORT FALSE CACHE BOOL
   "OMPT-support?")
 set(LIBOMP_OMPT_BLAME TRUE CACHE BOOL
   "OMPT-blame?")
 set(LIBOMP_OMPT_TRACE TRUE CACHE BOOL

 set(LIBOMP_DEFAULT_LIB_NAME libomp)
 if(${PROFILE_LIBRARY})
   set(LIBOMP_DEFAULT_LIB_NAME ${LIBOMP_DEFAULT_LIB_NAME}prof)
 endif()
 if(${STUBS_LIBRARY})
   set(LIBOMP_DEFAULT_LIB_NAME ${LIBOMP_DEFAULT_LIB_NAME}stubs)
 endif()
 set(LIBOMP_LIB_NAME ${LIBOMP_DEFAULT_LIB_NAME} CACHE STRING "Base OMP library name")
-set(LIBOMP_LIB_FILE ${LIBOMP_LIB_NAME}${CMAKE_SHARED_LIBRARY_SUFFIX})
+
+if(${LIBOMP_STATIC_LIBRARY})
+  set(LIBOMP_LIBRARY_SUFFIX ${CMAKE_STATIC_LIBRARY_SUFFIX})
+  set(LIBOMP_LIBRARY_KIND STATIC) 
+  set(LIBOMP_INSTALL_KIND ARCHIVE) 
+else()
+  set(LIBOMP_LIBRARY_SUFFIX ${CMAKE_SHARED_LIBRARY_SUFFIX})
+  set(LIBOMP_LIBRARY_KIND SHARED) 
+  set(LIBOMP_INSTALL_KIND LIBRARY) 
+endif()
+
+set(LIBOMP_LIB_FILE ${LIBOMP_LIB_NAME}${LIBOMP_LIBRARY_SUFFIX})
 
 # Print configuration after all variables are set.
 if(${LIBOMP_STANDALONE_BUILD})
   libomp_say("Operating System     -- ${CMAKE_SYSTEM_NAME}")
   libomp_say("Target Architecture  -- ${LIBOMP_ARCH}")
   if(${MIC})
     libomp_say("Intel(R) MIC Architecture    -- ${LIBOMP_MIC_ARCH}")
   endif()
   libomp_say("Build Type           -- ${CMAKE_BUILD_TYPE}")
   libomp_say("OpenMP Version       -- ${LIBOMP_OMP_VERSION}")
-  libomp_say("Lib Type             -- ${LIBOMP_LIB_TYPE}")
+  libomp_say("Library Kind         -- ${LIBOMP_LIBRARY_KIND}")
+  libomp_say("Library Type         -- ${LIBOMP_LIB_TYPE}")
   libomp_say("Fortran Modules      -- ${LIBOMP_FORTRAN_MODULES}")
   # will say development if all zeros
   if(${LIBOMP_VERSION_BUILD} STREQUAL 00000000)
     set(LIBOMP_BUILD Development)
   else()
     set(LIBOMP_BUILD ${LIBOMP_VERSION_BUILD})
   endif()
   libomp_say("Build                -- ${LIBOMP_BUILD}")

runtime/src/CMakeLists.txt

if(NOT ${LIBOMP_USE_STDCPPLIB})
   set(LIBOMP_LINKER_LANGUAGE C)
   set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES)
 else()
   set(LIBOMP_LINKER_LANGUAGE CXX)
 endif()
 
 # Add the OpenMP library
 libomp_get_ldflags(LIBOMP_CONFIGURED_LDFLAGS)
-add_library(omp SHARED ${LIBOMP_SOURCE_FILES})
+
+add_library(omp ${LIBOMP_LIBRARY_KIND} ${LIBOMP_SOURCE_FILES})
+
 set_target_properties(omp PROPERTIES
   PREFIX "" SUFFIX "" OUTPUT_NAME "${LIBOMP_LIB_FILE}"
   LINK_FLAGS "${LIBOMP_CONFIGURED_LDFLAGS}"
   LINKER_LANGUAGE ${LIBOMP_LINKER_LANGUAGE}
 )
 
 # Get the library's location within the build tree for the unit tester
 get_target_property(LIBOMP_LIBRARY_DIR omp LIBRARY_OUTPUT_DIRECTORY)
 if(NOT LIBOMP_LIBRARY_DIR)
   set(LIBOMP_LIBRARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
   set(LIBOMP_LIBRARY_DIR ${CMAKE_CURRENT_BINARY_DIR} PARENT_SCOPE)
 else()
   set(LIBOMP_LIBRARY_DIR ${LIBOMP_LIBRARY_DIR} PARENT_SCOPE)
 endif()
 
 # Add symbolic links to libomp
 if(NOT WIN32)
   add_custom_command(TARGET omp POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E create_symlink ${LIBOMP_LIB_FILE}
-      libgomp${CMAKE_SHARED_LIBRARY_SUFFIX}
+      libgomp${LIBOMP_LIBRARY_SUFFIX}
     COMMAND ${CMAKE_COMMAND} -E create_symlink ${LIBOMP_LIB_FILE}
-      libiomp5${CMAKE_SHARED_LIBRARY_SUFFIX}
+      libiomp5${LIBOMP_LIBRARY_SUFFIX}
     WORKING_DIRECTORY ${LIBOMP_LIBRARY_DIR}
   )
 endif()
 
 # Linking command will include libraries in LIBOMP_CONFIGURED_LIBFLAGS
 libomp_get_libflags(LIBOMP_CONFIGURED_LIBFLAGS)
 target_link_libraries(omp ${LIBOMP_CONFIGURED_LIBFLAGS} ${CMAKE_DL_LIBS})
 

 endif()
 if(WIN32)
   install(TARGETS omp RUNTIME DESTINATION bin)
   install(TARGETS ompimp ARCHIVE DESTINATION lib${LIBOMP_LIBDIR_SUFFIX})
   # Create aliases (regular copies) of the library for backwards compatibility
   set(LIBOMP_ALIASES "libiomp5md")
   foreach(alias IN LISTS LIBOMP_ALIASES)
     install(CODE "execute_process(COMMAND \"\${CMAKE_COMMAND}\" -E copy \"${LIBOMP_LIB_FILE}\"
-      \"${alias}${CMAKE_SHARED_LIBRARY_SUFFIX}\" WORKING_DIRECTORY \${CMAKE_INSTALL_PREFIX}/bin)")
+      \"${alias}${LIBOMP_LIBRARY_SUFFIX}\" WORKING_DIRECTORY \${CMAKE_INSTALL_PREFIX}/bin)")
     install(CODE "execute_process(COMMAND \"\${CMAKE_COMMAND}\" -E copy \"${LIBOMP_IMP_LIB_FILE}\"
-      \"${alias}${CMAKE_STATIC_LIBRARY_SUFFIX}\" WORKING_DIRECTORY \${CMAKE_INSTALL_PREFIX}/lib${LIBOMP_LIBDIR_SUFFIX})")
+      \"${alias}${LIBOMP_LIBRARY_SUFFIX}\" WORKING_DIRECTORY \${CMAKE_INSTALL_PREFIX}/lib${LIBOMP_LIBDIR_SUFFIX})")
   endforeach()
 else()
-  install(TARGETS omp LIBRARY DESTINATION lib${LIBOMP_LIBDIR_SUFFIX})
+
+  install(TARGETS omp ${LIBOMP_INSTALL_KIND} DESTINATION lib${LIBOMP_LIBDIR_SUFFIX})
+
   # Create aliases (symlinks) of the library for backwards compatibility
   set(LIBOMP_ALIASES "libgomp;libiomp5")
   foreach(alias IN LISTS LIBOMP_ALIASES)
     install(CODE "execute_process(COMMAND \"\${CMAKE_COMMAND}\" -E create_symlink \"${LIBOMP_LIB_FILE}\"
-      \"${alias}${CMAKE_SHARED_LIBRARY_SUFFIX}\" WORKING_DIRECTORY
+      \"${alias}${LIBOMP_LIBRARY_SUFFIX}\" WORKING_DIRECTORY
       \$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/lib${LIBOMP_LIBDIR_SUFFIX})")
   endforeach()
 endif()
 install(
   FILES
   ${CMAKE_CURRENT_BINARY_DIR}/omp.h
   DESTINATION ${LIBOMP_HEADERS_INSTALL_PATH}
 )