CMake/Modules/FindThreads.cmake

# - This module determines the thread library of the system.
# The following variables are set
#  CMAKE_THREAD_LIBS_INIT     - the thread library
#  CMAKE_USE_SPROC_INIT       - are we using sproc?
#  CMAKE_USE_WIN32_THREADS_INIT - using WIN32 threads?
#  CMAKE_USE_PTHREADS_INIT    - are we using pthreads
#  CMAKE_HP_PTHREADS_INIT     - are we using hp pthreads
# For systems with multiple thread libraries, caller can set
#  CMAKE_THREAD_PREFER_PTHREAD

#=============================================================================
# Copyright 2002-2009 Kitware, Inc.
#
# Distributed under the OSI-approved BSD License (the "License");
# see accompanying file Copyright.txt for details.
#
# This software is distributed WITHOUT ANY WARRANTY; without even the
# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the License for more information.
#=============================================================================
# (To distribute this file outside of CMake, substitute the full
#  License text for the above reference.)

include (CheckIncludeFiles)
include (CheckLibraryExists)
include (CheckSymbolExists)
set(Threads_FOUND FALSE)

# Do we have sproc?
if(CMAKE_SYSTEM MATCHES IRIX AND NOT CMAKE_THREAD_PREFER_PTHREAD)
  CHECK_INCLUDE_FILES("sys/types.h;sys/prctl.h"  CMAKE_HAVE_SPROC_H)
endif()

if(CMAKE_HAVE_SPROC_H AND NOT CMAKE_THREAD_PREFER_PTHREAD)
  # We have sproc
  set(CMAKE_USE_SPROC_INIT 1)
else()
  # Do we have pthreads?
  CHECK_INCLUDE_FILES("pthread.h" CMAKE_HAVE_PTHREAD_H)
  if(CMAKE_HAVE_PTHREAD_H)

    #
    # We have pthread.h
    # Let's check for the library now.
    #
    set(CMAKE_HAVE_THREADS_LIBRARY)
    if(NOT THREADS_HAVE_PTHREAD_ARG)
      # Check if pthread functions are in normal C library
      CHECK_SYMBOL_EXISTS(pthread_create pthread.h CMAKE_HAVE_LIBC_CREATE)
      if(CMAKE_HAVE_LIBC_CREATE)
        set(CMAKE_THREAD_LIBS_INIT "")
        set(CMAKE_HAVE_THREADS_LIBRARY 1)
        set(Threads_FOUND TRUE)
      endif()

      if(NOT CMAKE_HAVE_THREADS_LIBRARY)
        # Do we have -lpthreads
        CHECK_LIBRARY_EXISTS(pthreads pthread_create "" CMAKE_HAVE_PTHREADS_CREATE)
        if(CMAKE_HAVE_PTHREADS_CREATE)
          set(CMAKE_THREAD_LIBS_INIT "-lpthreads")
          set(CMAKE_HAVE_THREADS_LIBRARY 1)
          set(Threads_FOUND TRUE)
        endif()

        # Ok, how about -lpthread
        CHECK_LIBRARY_EXISTS(pthread pthread_create "" CMAKE_HAVE_PTHREAD_CREATE)
        if(CMAKE_HAVE_PTHREAD_CREATE)
          set(CMAKE_THREAD_LIBS_INIT "-lpthread")
          set(CMAKE_HAVE_THREADS_LIBRARY 1)
          set(Threads_FOUND TRUE)
        endif()

        if(CMAKE_SYSTEM MATCHES "SunOS.*")
          # On sun also check for -lthread
          CHECK_LIBRARY_EXISTS(thread thr_create "" CMAKE_HAVE_THR_CREATE)
          if(CMAKE_HAVE_THR_CREATE)
            set(CMAKE_THREAD_LIBS_INIT "-lthread")
            set(CMAKE_HAVE_THREADS_LIBRARY 1)
            set(Threads_FOUND TRUE)
          endif()
        endif()
      endif()
    endif()

    if(NOT CMAKE_HAVE_THREADS_LIBRARY)
      # If we did not found -lpthread, -lpthread, or -lthread, look for -pthread
      if("THREADS_HAVE_PTHREAD_ARG" MATCHES "^THREADS_HAVE_PTHREAD_ARG")
        message(STATUS "Check if compiler accepts -pthread")
        try_run(THREADS_PTHREAD_ARG THREADS_HAVE_PTHREAD_ARG
          ${CMAKE_BINARY_DIR}
          ${CMAKE_ROOT}/Modules/CheckForPthreads.c
          CMAKE_FLAGS -DLINK_LIBRARIES:STRING=-pthread
          COMPILE_OUTPUT_VARIABLE OUTPUT)

        if(THREADS_HAVE_PTHREAD_ARG)
          if(THREADS_PTHREAD_ARG STREQUAL "2")
            set(Threads_FOUND TRUE)
            message(STATUS "Check if compiler accepts -pthread - yes")
          else()
            message(STATUS "Check if compiler accepts -pthread - no")
            file(APPEND
              ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
              "Determining if compiler accepts -pthread returned ${THREADS_PTHREAD_ARG} instead of 2. The compiler had the following output:\n${OUTPUT}\n\n")
          endif()
        else()
          message(STATUS "Check if compiler accepts -pthread - no")
          file(APPEND
            ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
            "Determining if compiler accepts -pthread failed with the following output:\n${OUTPUT}\n\n")
        endif()

      endif()

      if(THREADS_HAVE_PTHREAD_ARG)
        set(Threads_FOUND TRUE)
        set(CMAKE_THREAD_LIBS_INIT "-pthread")
      endif()

    endif()
  endif()
endif()

if(CMAKE_THREAD_LIBS_INIT OR CMAKE_HAVE_LIBC_CREATE)
  set(CMAKE_USE_PTHREADS_INIT 1)
  set(Threads_FOUND TRUE)
endif()

if(CMAKE_SYSTEM MATCHES "Windows")
  set(CMAKE_USE_WIN32_THREADS_INIT 1)
  set(Threads_FOUND TRUE)
endif()

if(CMAKE_USE_PTHREADS_INIT)
  if(CMAKE_SYSTEM MATCHES "HP-UX-*")
    # Use libcma if it exists and can be used.  It provides more
    # symbols than the plain pthread library.  CMA threads
    # have actually been deprecated:
    #   http://docs.hp.com/en/B3920-90091/ch12s03.html#d0e11395
    #   http://docs.hp.com/en/947/d8.html
    # but we need to maintain compatibility here.
    # The CMAKE_HP_PTHREADS setting actually indicates whether CMA threads
    # are available.
    CHECK_LIBRARY_EXISTS(cma pthread_attr_create "" CMAKE_HAVE_HP_CMA)
    if(CMAKE_HAVE_HP_CMA)
      set(CMAKE_THREAD_LIBS_INIT "-lcma")
      set(CMAKE_HP_PTHREADS_INIT 1)
      set(Threads_FOUND TRUE)
    endif()
    set(CMAKE_USE_PTHREADS_INIT 1)
  endif()

  if(CMAKE_SYSTEM MATCHES "OSF1-V*")
    set(CMAKE_USE_PTHREADS_INIT 0)
    set(CMAKE_THREAD_LIBS_INIT )
  endif()

  if(CMAKE_SYSTEM MATCHES "CYGWIN_NT*")
    set(CMAKE_USE_PTHREADS_INIT 1)
    set(Threads_FOUND TRUE)
    set(CMAKE_THREAD_LIBS_INIT )
    set(CMAKE_USE_WIN32_THREADS_INIT 0)
  endif()
endif()

include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
FIND_PACKAGE_HANDLE_STANDARD_ARGS(Threads DEFAULT_MSG Threads_FOUND)