[CMake] Get rid of LLVM_DYLIB_EXPORT_ALL, and make it the default, add libLLVM-C on darwin to cover the C API needs.

[beanz]

Summary

We've had a lot of discussion in the past about the meaningful and useful default behaviors for the llvm-shlib tool. The original implementation was heavily geared toward Apple's use, and I think that was wrong. This patch seeks to correct that.

I've removed the LLVM_DYLIB_EXPORT_ALL variable and made libLLVM export everything by default.

I've also added a new target that is only built on Darwin for libLLVM-C as a library that re-exports the LLVM-C API. This library is not built on Linux because ELF doesn't support re-export libraries in the same way MachO does.

[axw]

Thanks, just a few small things. I'm not qualified to review the Apple-specific bits.

CMakeLists.txt

376

Did you mean to make this change? It's a pretty big change, and probably warrants some discussion on llvm-dev.

378

nit, differentiate description from option above?

tools/llvm-shlib/CMakeLists.txt

15

s/LLVM_DYLIB_EXPORT_ALL/LLVM_LINK_LLVM_DYLIB/
?

80

nit, I think "_LLVM || LLVM" is only necessary if targeting Darwin (with a _ prefix) as well as other platforms (with no _ prefix).

[beanz]

Thanks for the feedback. Updated patches incoming.

CMakeLists.txt

376

That was unintentional, but I do actually need to clean up how we set some of the defaults here. I think the default value for LLVM_BUILD_LLVM_DYLIB should effectively be LLVM_LINK_LLVM_DYLIB OR LLVM_BUILD_LLVM_C_DYLIB.

[beanz]

Updates based on feedback from Andrew.

[axw]

LGTM

CMakeLists.txt

 
 # You can configure which libraries from LLVM you want to include in the
 # shared library by setting LLVM_DYLIB_COMPONENTS to a semi-colon delimited
 # list of LLVM components. All component names handled by llvm-config are valid.
 if(NOT DEFINED LLVM_DYLIB_COMPONENTS)
   set(LLVM_DYLIB_COMPONENTS "all" CACHE STRING
     "Semicolon-separated list of components to include in libLLVM, or \"all\".")
 endif()
-option(LLVM_LINK_LLVM_DYLIB "Link tools against the libllvm dynamic library" OFF)
+option(LLVM_LINK_LLVM_DYLIB "Link tools against the libllvm dynamic library" ON)
 option(LLVM_BUILD_LLVM_DYLIB "Build libllvm dynamic library" ${LLVM_LINK_LLVM_DYLIB})
-option(LLVM_DYLIB_EXPORT_ALL "Export all symbols from libLLVM.dylib (default is C API only" ${LLVM_LINK_LLVM_DYLIB})
+option(LLVM_BUILD_LLVM_C_DYLIB "Build libllvm dynamic library" OFF)
 set(LLVM_DISABLE_LLVM_DYLIB_ATEXIT_DEFAULT ON)
 if (LLVM_LINK_LLVM_DYLIB)
   set(LLVM_DISABLE_LLVM_DYLIB_ATEXIT_DEFAULT OFF)
 endif()
 option(LLVM_DISABLE_LLVM_DYLIB_ATEXIT "Disable llvm-shlib's atexit destructors." ${LLVM_DISABLE_LLVM_DYLIB_ATEXIT_DEFAULT})
 if(LLVM_DISABLE_LLVM_DYLIB_ATEXIT)
   set(DISABLE_LLVM_DYLIB_ATEXIT 1)
 endif()

tools/llvm-shlib/CMakeLists.txt

 # This tool creates a shared library from the LLVM libraries. Generating this
 # library is enabled by setting LLVM_BUILD_LLVM_DYLIB=yes on the CMake
 # commandline. By default the shared library only exports the LLVM C API.
 
 add_definitions( -DLLVM_VERSION_INFO=\"${PACKAGE_VERSION}\" )
 
 set(SOURCES
   libllvm.cpp
   )
 
 llvm_map_components_to_libnames(LIB_NAMES ${LLVM_DYLIB_COMPONENTS})
 
 if(LLVM_LINK_LLVM_DYLIB)
-  if(NOT LLVM_DYLIB_EXPORT_ALL)
-    message(FATAL_ERROR "LLVM_DYLIB_EXPORT_ALL must be ON when LLVM_LINK_LLVM_DYLIB is ON")
+  if(LLVM_DYLIB_EXPORTED_SYMBOL_FILE)
+    message(WARNING "Using LLVM_DYLIB_EXPORT_ALL with LLVM_DYLIB_EXPORTED_SYMBOL_FILE may not work. Use at your own risk.")
   endif()
 
   # libLLVM.so should not have any dependencies on any other LLVM
   # shared libraries. When using the "all" pseudo-component,
   # LLVM_AVAILABLE_LIBS is added to the dependencies, which may
   # contain shared libraries (e.g. libLTO).
   #
   # Also exclude libLLVMTableGen for the following reasons:
   #  - it is only used by internal *-tblgen utilities;
   #  - it pollutes the global options space.
   foreach(lib ${LIB_NAMES})
     get_target_property(t ${lib} TYPE)
     if("${lib}" STREQUAL "LLVMTableGen")
     elseif("x${t}" STREQUAL "xSTATIC_LIBRARY")
       list(APPEND FILTERED_LIB_NAMES ${lib})
     endif()
   endforeach()
   set(LIB_NAMES ${FILTERED_LIB_NAMES})
 endif()
 
-if(NOT DEFINED LLVM_DYLIB_EXPORTED_SYMBOL_FILE)
-  # To get the export list for a single llvm library:
-  # nm ${LIB_PATH} | awk "/T _LLVM/ { print $3 }" | sort -u | sed -e "s/^_//g" > ${LIB_PATH}.exports
-
-  if (NOT LLVM_DYLIB_EXPORT_ALL)
-    if( WIN32 AND NOT CYGWIN )
-      message(FATAL_ERROR "Auto-generation not implemented for Win32 without GNU utils. Please specify LLVM_EXPORTED_SYMBOL_FILE.")
-    endif()
-
-    set(LLVM_EXPORTED_SYMBOL_FILE ${CMAKE_BINARY_DIR}/libllvm.exports)
-
-    foreach (lib ${LIB_NAMES})
-      set(LIB_DIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
-      set(LIB_NAME ${LIB_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}${lib})
-      set(LIB_PATH ${LIB_NAME}${CMAKE_STATIC_LIBRARY_SUFFIX})
-      set(LIB_EXPORTS_PATH ${LIB_NAME}.exports)
-      list(APPEND LLVM_DYLIB_REQUIRED_EXPORTS ${LIB_EXPORTS_PATH})
-
-      
-      add_custom_command(OUTPUT ${LIB_EXPORTS_PATH}
-        COMMAND nm ${LIB_PATH} | awk "/T _LLVM/ || /T LLVM/ { print $3 }" | sort -u | sed -e "s/^_//g" > ${LIB_EXPORTS_PATH}
-        WORKING_DIRECTORY ${LIB_DIR}
-        DEPENDS ${lib}
-        COMMENT "Generating Export list for ${lib}..."
-        VERBATIM )
-    endforeach ()
-
-    add_custom_command(OUTPUT ${LLVM_EXPORTED_SYMBOL_FILE}
-      COMMAND cat ${LLVM_DYLIB_REQUIRED_EXPORTS} > ${LLVM_EXPORTED_SYMBOL_FILE}
-      WORKING_DIRECTORY ${LIB_DIR}
-      DEPENDS ${LLVM_DYLIB_REQUIRED_EXPORTS}
-      COMMENT "Generating combined export list...")
-    add_custom_target(libLLVMExports DEPENDS ${LLVM_EXPORTED_SYMBOL_FILE})
-  endif()
-else()
+if(LLVM_DYLIB_EXPORTED_SYMBOL_FILE)
   set(LLVM_EXPORTED_SYMBOL_FILE ${LLVM_DYLIB_EXPORTED_SYMBOL_FILE})
   add_custom_target(libLLVMExports DEPENDS ${LLVM_EXPORTED_SYMBOL_FILE})
 endif()
 
 add_llvm_library(LLVM SHARED DISABLE_LLVM_LINK_LLVM_DYLIB ${SOURCES})
 
 list(REMOVE_DUPLICATES LIB_NAMES)
 if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux") # FIXME: It should be "GNU ld for elf"
   # GNU ld doesn't resolve symbols in the version script.
   set(LIB_NAMES -Wl,--whole-archive ${LIB_NAMES} -Wl,--no-whole-archive)
 elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
   set(LIB_NAMES -Wl,-all_load ${LIB_NAMES})
 endif()
 
 target_link_libraries(LLVM PRIVATE ${LIB_NAMES})
 
+if (APPLE)
+  set_property(TARGET LLVM APPEND_STRING PROPERTY
+              LINK_FLAGS
+              " -compatibility_version 1 -current_version ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")
+endif()
+
 if(TARGET libLLVMExports)
   add_dependencies(LLVM libLLVMExports)
 endif()
 
-if (APPLE)
-  set_property(TARGET LLVM APPEND_STRING PROPERTY
+if(LLVM_BUILD_LLVM_C_DYLIB)
+  # To get the export list for a single llvm library:
+  # nm ${LIB_PATH} | awk "/T _LLVM/ { print $3 }" | sort -u | sed -e "s/^_//g" > ${LIB_PATH}.exports
+
+  if(NOT APPLE)
+    message(FATAL_ERROR "Generating libLLVM-c is only supported on Darwin")
+  endif()
+
+  set(LLVM_EXPORTED_SYMBOL_FILE ${CMAKE_BINARY_DIR}/libllvm-c.exports)
+
+  set(LIB_DIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
+  set(LIB_NAME ${LIB_DIR}/${CMAKE_SHARED_LIBRARY_PREFIX}LLVM)
+  set(LIB_PATH ${LIB_NAME}${CMAKE_SHARED_LIBRARY_SUFFIX})
+  set(LIB_EXPORTS_PATH ${LIB_NAME}.exports)
+  list(APPEND LLVM_DYLIB_REQUIRED_EXPORTS ${LIB_EXPORTS_PATH})
+
+  add_custom_command(OUTPUT ${LLVM_EXPORTED_SYMBOL_FILE}
+    COMMAND nm ${LIB_PATH} | awk "/T _LLVM/ || /T LLVM/ { print $3 }" | sort -u | sed -e "s/^_//g" > ${LLVM_EXPORTED_SYMBOL_FILE}
+    WORKING_DIRECTORY ${LIB_DIR}
+    DEPENDS LLVM
+    COMMENT "Generating Export list for LLVM..."
+    VERBATIM )
+
+  add_custom_target(libLLVMCExports DEPENDS ${LLVM_EXPORTED_SYMBOL_FILE})
+
+  add_llvm_library(LLVM-C SHARED ${SOURCES})
+  
+  target_link_libraries(LLVM-C PUBLIC LLVM)
+  add_dependencies(LLVM-C libLLVMCExports)
+  
+  set_property(TARGET LLVM-C APPEND_STRING PROPERTY
               LINK_FLAGS
-              " -compatibility_version 1 -current_version ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")
+              " -compatibility_version 1 -current_version ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH} -Wl,-reexport_library ${LIB_PATH}")
 endif()