[CMake] Fix pthread handling for out-of-tree builds

[EricWF]

Summary

LLVM defines PTHREAD_LIB which is used by AddLLVM.cmake and various projects to correctly link the threading library when needed. Unfortunately PTHREAD_LIB is defined by LLVM's config-ix.cmake file which isn't installed and therefore can't be used when configuring out-of-tree builds. This causes such builds to fail since pthread isn't being correctly linked.

This patch attempts to fix that problem by renaming and exporting LLVM_PTHREAD_LIB as part of`LLVMConfig.cmake`. I renamed PTHREAD_LIB because It seemed likely to cause collisions with downstream users of LLVMConfig.cmake.

[mgorny]

cmake/modules/LLVMConfig.cmake.in

49

Are you sure that this is safe to do for every package doing find_package(LLVM)?

[EricWF]

cmake/modules/LLVMConfig.cmake.in

49

Perhaps not. I tested without it and it didn't immediately seem needed, at least on my platform. I'll look into moving or removing it.

[EricWF]

Address @mgorny's comments and don't set CMAKE_THREAD_PREFER_PTHREAD and THREADS_HAVE_PTHREAD_ARG in LLVMConfig. These options are only needed during the initial configuration and should not be set when LLVMConfig is included by downstream users code.

[beanz]

This looks reasonable to me.

[EricWF]

This patch and the dependencies were committed as r294690.

cmake/config-ix.cmake

 
 if(HAVE_LIBPTHREAD)
   # We want to find pthreads library and at the moment we do want to
   # have it reported as '-l<lib>' instead of '-pthread'.
   # TODO: switch to -pthread once the rest of the build system can deal with it.
   set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
   set(THREADS_HAVE_PTHREAD_ARG Off)
   find_package(Threads REQUIRED)
-  set(PTHREAD_LIB ${CMAKE_THREAD_LIBS_INIT})
+  set(LLVM_PTHREAD_LIB ${CMAKE_THREAD_LIBS_INIT})
 endif()
 
 # Don't look for these libraries on Windows. Also don't look for them if we're
 # using MSan, since uninstrumented third party code may call MSan interceptors
 # like strlen, leading to false positives.
 if( NOT PURE_WINDOWS AND NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
   if (LLVM_ENABLE_ZLIB)
     check_library_exists(z compress2 "" HAVE_LIBZ)

cmake/modules/AddLLVM.cmake

macro(add_llvm_executable name)
   llvm_config( ${name} ${USE_SHARED} ${LLVM_LINK_COMPONENTS} )
   if( LLVM_COMMON_DEPENDS )
     add_dependencies( ${name} ${LLVM_COMMON_DEPENDS} )
   endif( LLVM_COMMON_DEPENDS )
 
   if(NOT ARG_IGNORE_EXTERNALIZE_DEBUGINFO)
     llvm_externalize_debuginfo(${name})
   endif()
-  if (PTHREAD_LIB)
+  if (LLVM_PTHREAD_LIB)
     # libpthreads overrides some standard library symbols, so main
     # executable must be linked with it in order to provide consistent
     # API for all shared libaries loaded by this executable.
-    target_link_libraries(${name} ${PTHREAD_LIB})
+    target_link_libraries(${name} ${LLVM_PTHREAD_LIB})
   endif()
 endmacro(add_llvm_executable name)
 
 function(export_executable_symbols target)
   if (LLVM_EXPORTED_SYMBOL_FILE)
     # The symbol file should contain the symbols we want the executable to
     # export
     set_target_properties(${target} PROPERTIES ENABLE_EXPORTS 1)
function(add_unittest test_suite test_name)
 
   list(APPEND LLVM_LINK_COMPONENTS Support) # gtest needs it for raw_ostream
   add_llvm_executable(${test_name} IGNORE_EXTERNALIZE_DEBUGINFO NO_INSTALL_RPATH ${ARGN})
   set(outdir ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR})
   set_output_directory(${test_name} BINARY_DIR ${outdir} LIBRARY_DIR ${outdir})
   # libpthreads overrides some standard library symbols, so main
   # executable must be linked with it in order to provide consistent
   # API for all shared libaries loaded by this executable.
-  target_link_libraries(${test_name} gtest_main gtest ${PTHREAD_LIB})
+  target_link_libraries(${test_name} gtest_main gtest ${LLVM_PTHREAD_LIB})
 
   add_dependencies(${test_suite} ${test_name})
   get_target_property(test_suite_folder ${test_suite} FOLDER)
   if (NOT ${test_suite_folder} STREQUAL "NOTFOUND")
     set_property(TARGET ${test_name} PROPERTY FOLDER "${test_suite_folder}")
   endif ()
 endfunction()
 

cmake/modules/LLVMConfig.cmake.in

 set(LLVM_ENABLE_DIA_SDK @LLVM_ENABLE_DIA_SDK@)
 
 set(LLVM_NATIVE_ARCH @LLVM_NATIVE_ARCH@)
 
 set(LLVM_ENABLE_PIC @LLVM_ENABLE_PIC@)
 
 set(LLVM_BUILD_32_BITS @LLVM_BUILD_32_BITS@)
 
+if (NOT "@LLVM_PTHREAD_LIB@" STREQUAL "")
+  set(LLVM_PTHREAD_LIB "@LLVM_PTHREAD_LIB@")
+endif()
+
 set(LLVM_ENABLE_PLUGINS @LLVM_ENABLE_PLUGINS@)
 set(LLVM_EXPORT_SYMBOLS_FOR_PLUGINS @LLVM_EXPORT_SYMBOLS_FOR_PLUGINS@)
 set(LLVM_PLUGIN_EXT @LLVM_PLUGIN_EXT@)
 
 set(LLVM_ON_UNIX @LLVM_ON_UNIX@)
 set(LLVM_ON_WIN32 @LLVM_ON_WIN32@)
 
 set(LLVM_LIBDIR_SUFFIX @LLVM_LIBDIR_SUFFIX@)

examples/ParallelJIT/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Core
   ExecutionEngine
   Interpreter
   MC
   Support
   nativecodegen
   )
 
 add_llvm_example(ParallelJIT
   ParallelJIT.cpp
   )
 
-target_link_libraries(ParallelJIT ${PTHREAD_LIB})
+target_link_libraries(ParallelJIT ${LLVM_PTHREAD_LIB})

lib/CodeGen/CMakeLists.txt

add_llvm_library(LLVMCodeGen
   VirtRegMap.cpp
   WinEHPrepare.cpp
   XRayInstrumentation.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/CodeGen
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/CodeGen/PBQP
 
-  LINK_LIBS ${PTHREAD_LIB}
+  LINK_LIBS ${LLVM_PTHREAD_LIB}
 
   DEPENDS
   intrinsics_gen
   )
 
 add_subdirectory(SelectionDAG)
 add_subdirectory(AsmPrinter)
 add_subdirectory(MIRParser)
 add_subdirectory(GlobalISel)

lib/ExecutionEngine/IntelJITEvents/CMakeLists.txt

 include_directories( ${CMAKE_CURRENT_SOURCE_DIR}/.. )
 
 if( HAVE_LIBDL )
     set(LLVM_INTEL_JIT_LIBS ${CMAKE_DL_LIBS})
 endif()
 
-set(LLVM_INTEL_JIT_LIBS ${PTHREAD_LIB} ${LLVM_INTEL_JIT_LIBS})
+set(LLVM_INTEL_JIT_LIBS ${LLVM_PTHREAD_LIB} ${LLVM_INTEL_JIT_LIBS})
 
 
 add_llvm_library(LLVMIntelJITEvents
   IntelJITEventListener.cpp
   jitprofiling.c
 
   LINK_LIBS ${LLVM_INTEL_JIT_LIBS}
 )
 
 add_dependencies(LLVMIntelJITEvents LLVMCodeGen)

lib/Fuzzer/CMakeLists.txt

add_library(LLVMFuzzerNoMainObjects OBJECT
     FuzzerUtilDarwin.cpp
     FuzzerUtilLinux.cpp
     FuzzerUtilPosix.cpp
     FuzzerUtilWindows.cpp
     )
   add_library(LLVMFuzzerNoMain STATIC
     $<TARGET_OBJECTS:LLVMFuzzerNoMainObjects>
     )
-  target_link_libraries(LLVMFuzzerNoMain ${PTHREAD_LIB})
+  target_link_libraries(LLVMFuzzerNoMain ${LLVM_PTHREAD_LIB})
   add_library(LLVMFuzzer STATIC
     FuzzerMain.cpp
     $<TARGET_OBJECTS:LLVMFuzzerNoMainObjects>
     )
-  target_link_libraries(LLVMFuzzer ${PTHREAD_LIB})
+  target_link_libraries(LLVMFuzzer ${LLVM_PTHREAD_LIB})
 
   if( LLVM_INCLUDE_TESTS )
     add_subdirectory(test)
   endif()
 endif()

lib/Support/CMakeLists.txt

elseif( CMAKE_HOST_UNIX )
   if(LLVM_ENABLE_TERMINFO)
     if(HAVE_TERMINFO)
       set(system_libs ${system_libs} ${TERMINFO_LIBS})
     endif()
   endif()
   if( LLVM_ENABLE_THREADS AND HAVE_LIBATOMIC )
     set(system_libs ${system_libs} atomic)
   endif()
-  set(system_libs ${system_libs} ${PTHREAD_LIB})
+  set(system_libs ${system_libs} ${LLVM_PTHREAD_LIB})
   if ( LLVM_ENABLE_ZLIB AND HAVE_LIBZ )
     set(system_libs ${system_libs} z)
   endif()
   if( UNIX AND NOT (BEOS OR HAIKU) )
     set(system_libs ${system_libs} m)
   endif()
 endif( MSVC OR MINGW )
 

unittests/ExecutionEngine/Orc/CMakeLists.txt

add_llvm_unittest(OrcJITTests
   LazyEmittingLayerTest.cpp
   ObjectLinkingLayerTest.cpp
   ObjectTransformLayerTest.cpp
   OrcCAPITest.cpp
   OrcTestCommon.cpp
   RPCUtilsTest.cpp
   )
 
-target_link_libraries(OrcJITTests ${PTHREAD_LIB})
+target_link_libraries(OrcJITTests ${LLVM_PTHREAD_LIB})

unittests/Support/CMakeLists.txt

add_llvm_unittest(SupportTests
   formatted_raw_ostream_test.cpp
   raw_ostream_test.cpp
   raw_pwrite_stream_test.cpp
   raw_sha1_ostream_test.cpp
   xxhashTest.cpp
   )
 
 # ManagedStatic.cpp uses <pthread>.
-target_link_libraries(SupportTests ${PTHREAD_LIB})
+target_link_libraries(SupportTests ${LLVM_PTHREAD_LIB})

utils/unittest/CMakeLists.txt

 
 set(LLVM_REQUIRES_RTTI 1)
 add_definitions( -DGTEST_HAS_RTTI=0 )
 
 if (NOT LLVM_ENABLE_THREADS)
   add_definitions( -DGTEST_HAS_PTHREAD=0 )
 endif()
 
-find_library(PTHREAD_LIBRARY_PATH pthread)
-if (PTHREAD_LIBRARY_PATH)
+find_library(LLVM_PTHREAD_LIBRARY_PATH pthread)
+if (LLVM_PTHREAD_LIBRARY_PATH)
   list(APPEND LIBS pthread)
 endif()
 
 add_llvm_library(gtest
   googletest/src/gtest-all.cc
   googlemock/src/gmock-all.cc
 
   LINK_LIBS