path: root/Modules/ExternalProject.cmake

# - Create custom targets to build projects in external trees
# The 'ExternalProject_Add' function creates a custom target to drive
# download, update/patch, configure, build, install and test steps of an
# external project:
#  ExternalProject_Add(<name>    # Name for custom target
#    [DEPENDS projects...]       # Targets on which the project depends
#    [PREFIX dir]                # Root dir for entire project
#    [LIST_SEPARATOR sep]        # Sep to be replaced by ; in cmd lines
#    [TMP_DIR dir]               # Directory to store temporary files
#    [STAMP_DIR dir]             # Directory to store step timestamps
#   #--Download step--------------
#    [DOWNLOAD_DIR dir]          # Directory to store downloaded files
#    [DOWNLOAD_COMMAND cmd...]   # Command to download source tree
#    [CVS_REPOSITORY cvsroot]    # CVSROOT of CVS repository
#    [CVS_MODULE mod]            # Module to checkout from CVS repo
#    [CVS_TAG tag]               # Tag to checkout from CVS repo
#    [SVN_REPOSITORY url]        # URL of Subversion repo
#    [SVN_REVISION rev]          # Revision to checkout from Subversion repo
#    [SVN_USERNAME john ]        # Username for Subversion checkout and update
#    [SVN_PASSWORD doe ]         # Password for Subversion checkout and update
#    [SVN_TRUST_CERT 1 ]         # Trust the Subversion server site certificate
#    [GIT_REPOSITORY url]        # URL of git repo
#    [GIT_TAG tag]               # Git branch name, commit id or tag
#    [HG_REPOSITORY url]         # URL of mercurial repo
#    [HG_TAG tag]                # Mercurial branch name, commit id or tag
#    [URL /.../src.tgz]          # Full path or URL of source
#    [URL_HASH ALGO=value]       # Hash of file at URL
#    [URL_MD5 md5]               # Equivalent to URL_HASH MD5=md5
#    [SSL_VERIFYPEER bool]       # Should certificate for https be checked
#    [CAINFO_FILE file]          # Path to a certificate authority file
#    [TIMEOUT seconds]           # Time allowed for file download operations
#   #--Update/Patch step----------
#    [UPDATE_COMMAND cmd...]     # Source work-tree update command
#    [PATCH_COMMAND cmd...]      # Command to patch downloaded source
#   #--Configure step-------------
#    [SOURCE_DIR dir]            # Source dir to be used for build
#    [CONFIGURE_COMMAND cmd...]  # Build tree configuration command
#    [CMAKE_COMMAND /.../cmake]  # Specify alternative cmake executable
#    [CMAKE_GENERATOR gen]       # Specify generator for native build
#    [CMAKE_ARGS args...]        # Arguments to CMake command line
#    [CMAKE_CACHE_ARGS args...]  # Initial cache arguments, of the form -Dvar:string=on
#   #--Build step-----------------
#    [BINARY_DIR dir]            # Specify build dir location
#    [BUILD_COMMAND cmd...]      # Command to drive the native build
#    [BUILD_IN_SOURCE 1]         # Use source dir for build dir
#   #--Install step---------------
#    [INSTALL_DIR dir]           # Installation prefix
#    [INSTALL_COMMAND cmd...]    # Command to drive install after build
#   #--Test step------------------
#    [TEST_BEFORE_INSTALL 1]     # Add test step executed before install step
#    [TEST_AFTER_INSTALL 1]      # Add test step executed after install step
#    [TEST_COMMAND cmd...]       # Command to drive test
#   #--Output logging-------------
#    [LOG_DOWNLOAD 1]            # Wrap download in script to log output
#    [LOG_UPDATE 1]              # Wrap update in script to log output
#    [LOG_CONFIGURE 1]           # Wrap configure in script to log output
#    [LOG_BUILD 1]               # Wrap build in script to log output
#    [LOG_TEST 1]                # Wrap test in script to log output
#    [LOG_INSTALL 1]             # Wrap install in script to log output
#   #--Custom targets-------------
#    [STEP_TARGETS st1 st2 ...]  # Generate custom targets for these steps
#    )
# The *_DIR options specify directories for the project, with default
# directories computed as follows.
# If the PREFIX option is given to ExternalProject_Add() or the EP_PREFIX
# directory property is set, then an external project is built and installed
# under the specified prefix:
#   TMP_DIR      = <prefix>/tmp
#   STAMP_DIR    = <prefix>/src/<name>-stamp
#   DOWNLOAD_DIR = <prefix>/src
#   SOURCE_DIR   = <prefix>/src/<name>
#   BINARY_DIR   = <prefix>/src/<name>-build
#   INSTALL_DIR  = <prefix>
# Otherwise, if the EP_BASE directory property is set then components
# of an external project are stored under the specified base:
#   TMP_DIR      = <base>/tmp/<name>
#   STAMP_DIR    = <base>/Stamp/<name>
#   DOWNLOAD_DIR = <base>/Download/<name>
#   SOURCE_DIR   = <base>/Source/<name>
#   BINARY_DIR   = <base>/Build/<name>
#   INSTALL_DIR  = <base>/Install/<name>
# If no PREFIX, EP_PREFIX, or EP_BASE is specified then the default
# is to set PREFIX to "<name>-prefix".
# Relative paths are interpreted with respect to the build directory
# corresponding to the source directory in which ExternalProject_Add is
# invoked.
#
# If SOURCE_DIR is explicitly set to an existing directory the project
# will be built from it.
# Otherwise a download step must be specified using one of the
# DOWNLOAD_COMMAND, CVS_*, SVN_*, or URL options.
# The URL option may refer locally to a directory or source tarball,
# or refer to a remote tarball (e.g. http://.../src.tgz).
#
# The 'ExternalProject_Add_Step' function adds a custom step to an external
# project:
#  ExternalProject_Add_Step(<name> <step> # Names of project and custom step
#    [COMMAND cmd...]        # Command line invoked by this step
#    [COMMENT "text..."]     # Text printed when step executes
#    [DEPENDEES steps...]    # Steps on which this step depends
#    [DEPENDERS steps...]    # Steps that depend on this step
#    [DEPENDS files...]      # Files on which this step depends
#    [ALWAYS 1]              # No stamp file, step always runs
#    [WORKING_DIRECTORY dir] # Working directory for command
#    [LOG 1]                 # Wrap step in script to log output
#    )
# The command line, comment, and working directory of every standard
# and custom step is processed to replace tokens
# <SOURCE_DIR>,
# <BINARY_DIR>,
# <INSTALL_DIR>,
# and <TMP_DIR>
# with corresponding property values.
#
# The 'ExternalProject_Get_Property' function retrieves external project
# target properties:
#  ExternalProject_Get_Property(<name> [prop1 [prop2 [...]]])
# It stores property values in variables of the same name.
# Property names correspond to the keyword argument names of
# 'ExternalProject_Add'.
#
# The 'ExternalProject_Add_StepTargets' function generates custom targets for
# the steps listed:
#  ExternalProject_Add_StepTargets(<name> [step1 [step2 [...]]])
#
# If STEP_TARGETS is set then ExternalProject_Add_StepTargets is automatically
# called at the end of matching calls to ExternalProject_Add_Step. Pass
# STEP_TARGETS explicitly to individual ExternalProject_Add calls, or
# implicitly to all ExternalProject_Add calls by setting the directory property
# EP_STEP_TARGETS.
#
# If STEP_TARGETS is not set, clients may still manually call
# ExternalProject_Add_StepTargets after calling ExternalProject_Add or
# ExternalProject_Add_Step.
#
# This functionality is provided to make it easy to drive the steps
# independently of each other by specifying targets on build command lines.
# For example, you may be submitting to a sub-project based dashboard, where
# you want to drive the configure portion of the build, then submit to the
# dashboard, followed by the build portion, followed by tests. If you invoke
# a custom target that depends on a step halfway through the step dependency
# chain, then all the previous steps will also run to ensure everything is
# up to date.
#
# For example, to drive configure, build and test steps independently for each
# ExternalProject_Add call in your project, write the following line prior to
# any ExternalProject_Add calls in your CMakeLists file:
#
#   set_property(DIRECTORY PROPERTY EP_STEP_TARGETS configure build test)

#=============================================================================
# Copyright 2008-2012 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.)

# Pre-compute a regex to match documented keywords for each command.
math(EXPR _ep_documentation_line_count "${CMAKE_CURRENT_LIST_LINE} - 16")
file(STRINGS "${CMAKE_CURRENT_LIST_FILE}" lines
     LIMIT_COUNT ${_ep_documentation_line_count}
     REGEX "^#  (  \\[[A-Z0-9_]+ [^]]*\\] +#.*$|[A-Za-z0-9_]+\\()")
foreach(line IN LISTS lines)
  if("${line}" MATCHES "^#  [A-Za-z0-9_]+\\(")
    if(_ep_func)
      set(_ep_keywords_${_ep_func} "${_ep_keywords_${_ep_func}})$")
    endif()
    string(REGEX REPLACE "^#  ([A-Za-z0-9_]+)\\(.*" "\\1" _ep_func "${line}")
    #message("function [${_ep_func}]")
    set(_ep_keywords_${_ep_func} "^(")
    set(_ep_keyword_sep)
  else()
    string(REGEX REPLACE "^#    \\[([A-Z0-9_]+) .*" "\\1" _ep_key "${line}")
    #message("  keyword [${_ep_key}]")
    set(_ep_keywords_${_ep_func}
      "${_ep_keywords_${_ep_func}}${_ep_keyword_sep}${_ep_key}")
    set(_ep_keyword_sep "|")
  endif()
endforeach()
if(_ep_func)
  set(_ep_keywords_${_ep_func} "${_ep_keywords_${_ep_func}})$")
endif()

# Save regex matching supported hash algorithm names.
set(_ep_hash_algos "MD5|SHA1|SHA224|SHA256|SHA384|SHA512")
set(_ep_hash_regex "^(${_ep_hash_algos})=([0-9A-Fa-f]+)$")

function(_ep_parse_arguments f name ns args)
  # Transfer the arguments to this function into target properties for the
  # new custom target we just added so that we can set up all the build steps
  # correctly based on target properties.
  #
  # We loop through ARGN and consider the namespace starting with an
  # upper-case letter followed by at least two more upper-case letters,
  # numbers or underscores to be keywords.
  set(key)

  foreach(arg IN LISTS args)
    set(is_value 1)

    if(arg MATCHES "^[A-Z][A-Z0-9_][A-Z0-9_]+$" AND
        NOT ((arg STREQUAL "${key}") AND (key STREQUAL "COMMAND")) AND
        NOT arg MATCHES "^(TRUE|FALSE)$")
      if(_ep_keywords_${f} AND arg MATCHES "${_ep_keywords_${f}}")
        set(is_value 0)
      endif()
    endif()

    if(is_value)
      if(key)
        # Value
        if(NOT arg STREQUAL "")
          set_property(TARGET ${name} APPEND PROPERTY ${ns}${key} "${arg}")
        else()
          get_property(have_key TARGET ${name} PROPERTY ${ns}${key} SET)
          if(have_key)
            get_property(value TARGET ${name} PROPERTY ${ns}${key})
            set_property(TARGET ${name} PROPERTY ${ns}${key} "${value};${arg}")
          else()
            set_property(TARGET ${name} PROPERTY ${ns}${key} "${arg}")
          endif()
        endif()
      else()
        # Missing Keyword
        message(AUTHOR_WARNING "value '${arg}' with no previous keyword in ${f}")
      endif()
    else()
      set(key "${arg}")
    endif()
  endforeach()
endfunction()


define_property(DIRECTORY PROPERTY "EP_BASE" INHERITED
  BRIEF_DOCS "Base directory for External Project storage."
  FULL_DOCS
  "See documentation of the ExternalProject_Add() function in the "
  "ExternalProject module."
  )

define_property(DIRECTORY PROPERTY "EP_PREFIX" INHERITED
  BRIEF_DOCS "Top prefix for External Project storage."
  FULL_DOCS
  "See documentation of the ExternalProject_Add() function in the "
  "ExternalProject module."
  )

define_property(DIRECTORY PROPERTY "EP_STEP_TARGETS" INHERITED
  BRIEF_DOCS
  "List of ExternalProject steps that automatically get corresponding targets"
  FULL_DOCS
  "See documentation of the ExternalProject_Add_StepTargets() function in the "
  "ExternalProject module."
  )


function(_ep_write_gitclone_script script_filename source_dir git_EXECUTABLE git_repository git_tag src_name work_dir gitclone_infofile gitclone_stampfile)
  file(WRITE ${script_filename}
"if(\"${git_tag}\" STREQUAL \"\")
  message(FATAL_ERROR \"Tag for git checkout should not be empty.\")
endif()

set(run 0)

if(\"${gitclone_infofile}\" IS_NEWER_THAN \"${gitclone_stampfile}\")
  set(run 1)
endif()

if(NOT run)
  message(STATUS \"Avoiding repeated git clone, stamp file is up to date: '${gitclone_stampfile}'\")
  return()
endif()

execute_process(
  COMMAND \${CMAKE_COMMAND} -E remove_directory \"${source_dir}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to remove directory: '${source_dir}'\")
endif()

execute_process(
  COMMAND \"${git_EXECUTABLE}\" clone \"${git_repository}\" \"${src_name}\"
  WORKING_DIRECTORY \"${work_dir}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to clone repository: '${git_repository}'\")
endif()

execute_process(
  COMMAND \"${git_EXECUTABLE}\" checkout ${git_tag}
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to checkout tag: '${git_tag}'\")
endif()

execute_process(
  COMMAND \"${git_EXECUTABLE}\" submodule init
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to init submodules in: '${work_dir}/${src_name}'\")
endif()

execute_process(
  COMMAND \"${git_EXECUTABLE}\" submodule update --recursive
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to update submodules in: '${work_dir}/${src_name}'\")
endif()

# Complete success, update the script-last-run stamp file:
#
execute_process(
  COMMAND \${CMAKE_COMMAND} -E copy
    \"${gitclone_infofile}\"
    \"${gitclone_stampfile}\"
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to copy script-last-run stamp file: '${gitclone_stampfile}'\")
endif()

"
)

endfunction()

function(_ep_write_hgclone_script script_filename source_dir hg_EXECUTABLE hg_repository hg_tag src_name work_dir hgclone_infofile hgclone_stampfile)
  file(WRITE ${script_filename}
"if(\"${hg_tag}\" STREQUAL \"\")
  message(FATAL_ERROR \"Tag for hg checkout should not be empty.\")
endif()

set(run 0)

if(\"${hgclone_infofile}\" IS_NEWER_THAN \"${hgclone_stampfile}\")
  set(run 1)
endif()

if(NOT run)
  message(STATUS \"Avoiding repeated hg clone, stamp file is up to date: '${hgclone_stampfile}'\")
  return()
endif()

execute_process(
  COMMAND \${CMAKE_COMMAND} -E remove_directory \"${source_dir}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to remove directory: '${source_dir}'\")
endif()

execute_process(
  COMMAND \"${hg_EXECUTABLE}\" clone \"${hg_repository}\" \"${src_name}\"
  WORKING_DIRECTORY \"${work_dir}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to clone repository: '${hg_repository}'\")
endif()

execute_process(
  COMMAND \"${hg_EXECUTABLE}\" update ${hg_tag}
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to checkout tag: '${hg_tag}'\")
endif()

# Complete success, update the script-last-run stamp file:
#
execute_process(
  COMMAND \${CMAKE_COMMAND} -E copy
    \"${hgclone_infofile}\"
    \"${hgclone_stampfile}\"
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to copy script-last-run stamp file: '${hgclone_stampfile}'\")
endif()

"
)

endfunction()


function(_ep_write_downloadfile_script script_filename remote local timeout hash ssl_verify cainfo_file)
  if(timeout)
    set(timeout_args TIMEOUT ${timeout})
    set(timeout_msg "${timeout} seconds")
  else()
    set(timeout_args "# no TIMEOUT")
    set(timeout_msg "none")
  endif()

  if("${hash}" MATCHES "${_ep_hash_regex}")
    set(hash_args EXPECTED_HASH ${CMAKE_MATCH_1} ${CMAKE_MATCH_2})
  else()
    set(hash_args "# no EXPECTED_HASH")
  endif()
  # check for curl globals in the project
  if(DEFINED CMAKE_CURLOPT_SSL_VERIFYPEER)
    set(ssl_verify "set(CMAKE_CURLOPT_SSL_VERIFYPEER ${CMAKE_CURLOPT_SSL_VERIFYPEER})")
  endif()
  if(DEFINED CMAKE_CURLOPT_CAINFO_FILE)
    set(ssl_cainfo "set(CMAKE_CURLOPT_CAINFO_FILE \"${CMAKE_CURLOPT_CAINFO_FILE}\")")
  endif()

  # now check for curl locals so that the local values
  # will override the globals

  # check for ssl_verify argument
  string(LENGTH "${ssl_verify}" ssl_verify_len)
  if(ssl_verify_len GREATER 0)
    set(ssl_verify "set(CMAKE_CURLOPT_SSL_VERIFYPEER ${ssl_verify})")
  endif()
  # check for cainfo_file argument
  string(LENGTH "${cainfo_file}" cainfo_file_len)
  if(cainfo_file_len GREATER 0)
    set(ssl_cainfo "set(CMAKE_CURLOPT_CAINFO_FILE \"${cainfo_file}\")")
  endif()

  file(WRITE ${script_filename}
"message(STATUS \"downloading...
     src='${remote}'
     dst='${local}'
     timeout='${timeout_msg}'\")

${ssl_verify}
${ssl_cainfo}

file(DOWNLOAD
  \"${remote}\"
  \"${local}\"
  SHOW_PROGRESS
  ${hash_args}
  ${timeout_args}
  STATUS status
  LOG log)

list(GET status 0 status_code)
list(GET status 1 status_string)

if(NOT status_code EQUAL 0)
  message(FATAL_ERROR \"error: downloading '${remote}' failed
  status_code: \${status_code}
  status_string: \${status_string}
  log: \${log}
\")
endif()

message(STATUS \"downloading... done\")
"
)

endfunction()


function(_ep_write_verifyfile_script script_filename local hash)
  if("${hash}" MATCHES "${_ep_hash_regex}")
    set(algo "${CMAKE_MATCH_1}")
    string(TOLOWER "${CMAKE_MATCH_2}" expect_value)
    set(script_content "set(expect_value \"${expect_value}\")
file(${algo} \"\${file}\" actual_value)
if(\"\${actual_value}\" STREQUAL \"\${expect_value}\")
  message(STATUS \"verifying file... done\")
else()
  message(FATAL_ERROR \"error: ${algo} hash of
  \${file}
does not match expected value
  expected: \${expect_value}
    actual: \${actual_value}
\")
endif()")
  else()
    set(script_content "message(STATUS \"verifying file... warning: did not verify file - no URL_HASH specified?\")")
  endif()
  file(WRITE ${script_filename} "set(file \"${local}\")
message(STATUS \"verifying file...
     file='\${file}'\")
${script_content}
")
endfunction()


function(_ep_write_extractfile_script script_filename name filename directory)
  set(args "")

  if(filename MATCHES "(\\.|=)(bz2|tar\\.gz|tgz|zip)$")
    set(args xfz)
  endif()

  if(filename MATCHES "(\\.|=)tar$")
    set(args xf)
  endif()

  if(args STREQUAL "")
    message(SEND_ERROR "error: do not know how to extract '${filename}' -- known types are .bz2, .tar, .tar.gz, .tgz and .zip")
    return()
  endif()

  file(WRITE ${script_filename}
"# Make file names absolute:
#
get_filename_component(filename \"${filename}\" ABSOLUTE)
get_filename_component(directory \"${directory}\" ABSOLUTE)

message(STATUS \"extracting...
     src='\${filename}'
     dst='\${directory}'\")

if(NOT EXISTS \"\${filename}\")
  message(FATAL_ERROR \"error: file to extract does not exist: '\${filename}'\")
endif()

# Prepare a space for extracting:
#
set(i 1234)
while(EXISTS \"\${directory}/../ex-${name}\${i}\")
  math(EXPR i \"\${i} + 1\")
endwhile()
set(ut_dir \"\${directory}/../ex-${name}\${i}\")
file(MAKE_DIRECTORY \"\${ut_dir}\")

# Extract it:
#
message(STATUS \"extracting... [tar ${args}]\")
execute_process(COMMAND \${CMAKE_COMMAND} -E tar ${args} \${filename}
  WORKING_DIRECTORY \${ut_dir}
  RESULT_VARIABLE rv)

if(NOT rv EQUAL 0)
  message(STATUS \"extracting... [error clean up]\")
  file(REMOVE_RECURSE \"\${ut_dir}\")
  message(FATAL_ERROR \"error: extract of '\${filename}' failed\")
endif()

# Analyze what came out of the tar file:
#
message(STATUS \"extracting... [analysis]\")
file(GLOB contents \"\${ut_dir}/*\")
list(LENGTH contents n)
if(NOT n EQUAL 1 OR NOT IS_DIRECTORY \"\${contents}\")
  set(contents \"\${ut_dir}\")
endif()

# Move \"the one\" directory to the final directory:
#
message(STATUS \"extracting... [rename]\")
file(REMOVE_RECURSE \${directory})
get_filename_component(contents \${contents} ABSOLUTE)
file(RENAME \${contents} \${directory})

# Clean up:
#
message(STATUS \"extracting... [clean up]\")
file(REMOVE_RECURSE \"\${ut_dir}\")

message(STATUS \"extracting... done\")
"
)

endfunction()


function(_ep_set_directories name)
  get_property(prefix TARGET ${name} PROPERTY _EP_PREFIX)
  if(NOT prefix)
    get_property(prefix DIRECTORY PROPERTY EP_PREFIX)
    if(NOT prefix)
      get_property(base DIRECTORY PROPERTY EP_BASE)
      if(NOT base)
        set(prefix "${name}-prefix")
      endif()
    endif()
  endif()
  if(prefix)
    set(tmp_default "${prefix}/tmp")
    set(download_default "${prefix}/src")
    set(source_default "${prefix}/src/${name}")
    set(binary_default "${prefix}/src/${name}-build")
    set(stamp_default "${prefix}/src/${name}-stamp")
    set(install_default "${prefix}")
  else()
    set(tmp_default "${base}/tmp/${name}")
    set(download_default "${base}/Download/${name}")
    set(source_default "${base}/Source/${name}")
    set(binary_default "${base}/Build/${name}")
    set(stamp_default "${base}/Stamp/${name}")
    set(install_default "${base}/Install/${name}")
  endif()
  get_property(build_in_source TARGET ${name} PROPERTY _EP_BUILD_IN_SOURCE)
  if(build_in_source)
    get_property(have_binary_dir TARGET ${name} PROPERTY _EP_BINARY_DIR SET)
    if(have_binary_dir)
      message(FATAL_ERROR
        "External project ${name} has both BINARY_DIR and BUILD_IN_SOURCE!")
    endif()
  endif()
  set(top "${CMAKE_CURRENT_BINARY_DIR}")
  set(places stamp download source binary install tmp)
  foreach(var ${places})
    string(TOUPPER "${var}" VAR)
    get_property(${var}_dir TARGET ${name} PROPERTY _EP_${VAR}_DIR)
    if(NOT ${var}_dir)
      set(${var}_dir "${${var}_default}")
    endif()
    if(NOT IS_ABSOLUTE "${${var}_dir}")
      get_filename_component(${var}_dir "${top}/${${var}_dir}" ABSOLUTE)
    endif()
    set_property(TARGET ${name} PROPERTY _EP_${VAR}_DIR "${${var}_dir}")
  endforeach()
  if(build_in_source)
    get_property(source_dir TARGET ${name} PROPERTY _EP_SOURCE_DIR)
    set_property(TARGET ${name} PROPERTY _EP_BINARY_DIR "${source_dir}")
  endif()

  # Make the directories at CMake configure time *and* add a custom command
  # to make them at build time. They need to exist at makefile generation
  # time for Borland make and wmake so that CMake may generate makefiles
  # with "cd C:\short\paths\with\no\spaces" commands in them.
  #
  # Additionally, the add_custom_command is still used in case somebody
  # removes one of the necessary directories and tries to rebuild without
  # re-running cmake.
  foreach(var ${places})
    string(TOUPPER "${var}" VAR)
    get_property(dir TARGET ${name} PROPERTY _EP_${VAR}_DIR)
    file(MAKE_DIRECTORY "${dir}")
    if(NOT EXISTS "${dir}")
      message(FATAL_ERROR "dir '${dir}' does not exist after file(MAKE_DIRECTORY)")
    endif()
  endforeach()
endfunction()


# IMPORTANT: this MUST be a macro and not a function because of the
# in-place replacements that occur in each ${var}
#
macro(_ep_replace_location_tags target_name)
  set(vars ${ARGN})
  foreach(var ${vars})
    if(${var})
      foreach(dir SOURCE_DIR BINARY_DIR INSTALL_DIR TMP_DIR)
        get_property(val TARGET ${target_name} PROPERTY _EP_${dir})
        string(REPLACE "<${dir}>" "${val}" ${var} "${${var}}")
      endforeach()
    endif()
  endforeach()
endmacro()


function(_ep_write_initial_cache target_name script_filename args)
  # Write out values into an initial cache, that will be passed to CMake with -C
  set(script_initial_cache "")
  set(regex "^([^:]+):([^=]+)=(.*)$")
  set(setArg "")
  foreach(line ${args})
    if("${line}" MATCHES "^-D")
      if(setArg)
        # This is required to build up lists in variables, or complete an entry
        set(setArg "${setArg}${accumulator}\" CACHE ${type} \"Initial cache\" FORCE)")
        set(script_initial_cache "${script_initial_cache}\n${setArg}")
        set(accumulator "")
        set(setArg "")
      endif()
      string(REGEX REPLACE "^-D" "" line ${line})
      if("${line}" MATCHES "${regex}")
        string(REGEX MATCH "${regex}" match "${line}")
        set(name "${CMAKE_MATCH_1}")
        set(type "${CMAKE_MATCH_2}")
        set(value "${CMAKE_MATCH_3}")
        set(setArg "set(${name} \"${value}")
      else()
        message(WARNING "Line '${line}' does not match regex. Ignoring.")
      endif()
    else()
      # Assume this is a list to append to the last var
      set(accumulator "${accumulator};${line}")
    endif()
  endforeach()
  # Catch the final line of the args
  if(setArg)
    set(setArg "${setArg}${accumulator}\" CACHE ${type} \"Initial cache\" FORCE)")
    set(script_initial_cache "${script_initial_cache}\n${setArg}")
  endif()
  # Replace location tags.
  _ep_replace_location_tags(${target_name} script_initial_cache)
  # Write out the initial cache file to the location specified.
  if(NOT EXISTS "${script_filename}.in")
    file(WRITE "${script_filename}.in" "\@script_initial_cache\@\n")
  endif()
  configure_file("${script_filename}.in" "${script_filename}")
endfunction()


function(ExternalProject_Get_Property name)
  foreach(var ${ARGN})
    string(TOUPPER "${var}" VAR)
    get_property(${var} TARGET ${name} PROPERTY _EP_${VAR})
    if(NOT ${var})
      message(FATAL_ERROR "External project \"${name}\" has no ${var}")
    endif()
    set(${var} "${${var}}" PARENT_SCOPE)
  endforeach()
endfunction()


function(_ep_get_configure_command_id name cfg_cmd_id_var)
  get_target_property(cmd ${name} _EP_CONFIGURE_COMMAND)

  if(cmd STREQUAL "")
    # Explicit empty string means no configure step for this project
    set(${cfg_cmd_id_var} "none" PARENT_SCOPE)
  else()
    if(NOT cmd)
      # Default is "use cmake":
      set(${cfg_cmd_id_var} "cmake" PARENT_SCOPE)
    else()
      # Otherwise we have to analyze the value:
      if(cmd MATCHES "^[^;]*/configure")
        set(${cfg_cmd_id_var} "configure" PARENT_SCOPE)
      elseif(cmd MATCHES "^[^;]*/cmake" AND NOT cmd MATCHES ";-[PE];")
        set(${cfg_cmd_id_var} "cmake" PARENT_SCOPE)
      elseif(cmd MATCHES "config")
        set(${cfg_cmd_id_var} "configure" PARENT_SCOPE)
      else()
        set(${cfg_cmd_id_var} "unknown:${cmd}" PARENT_SCOPE)
      endif()
    endif()
  endif()
endfunction()


function(_ep_get_build_command name step cmd_var)
  set(cmd "${${cmd_var}}")
  if(NOT cmd)
    set(args)
    _ep_get_configure_command_id(${name} cfg_cmd_id)
    if(cfg_cmd_id STREQUAL "cmake")
      # CMake project.  Select build command based on generator.
      get_target_property(cmake_generator ${name} _EP_CMAKE_GENERATOR)
      if("${CMAKE_GENERATOR}" MATCHES "Make" AND
         ("${cmake_generator}" MATCHES "Make" OR NOT cmake_generator))
        # The project uses the same Makefile generator.  Use recursive make.
        set(cmd "$(MAKE)")
        if(step STREQUAL "INSTALL")
          set(args install)
        endif()
        if(step STREQUAL "TEST")
          set(args test)
        endif()
      else()
        # Drive the project with "cmake --build".
        get_target_property(cmake_command ${name} _EP_CMAKE_COMMAND)
        if(cmake_command)
          set(cmd "${cmake_command}")
        else()
          set(cmd "${CMAKE_COMMAND}")
        endif()
        set(args --build ${binary_dir} --config ${CMAKE_CFG_INTDIR})
        if(step STREQUAL "INSTALL")
          list(APPEND args --target install)
        endif()
        # But for "TEST" drive the project with corresponding "ctest".
        if(step STREQUAL "TEST")
          string(REGEX REPLACE "^(.*/)cmake([^/]*)$" "\\1ctest\\2" cmd "${cmd}")
          set(args "")
        endif()
      endif()
    else()
      # Non-CMake project.  Guess "make" and "make install" and "make test".
      if("${CMAKE_GENERATOR}" MATCHES "Makefiles")
        # Try to get the parallel arguments
        set(cmd "$(MAKE)")
      else()
        set(cmd "make")
      endif()
      if(step STREQUAL "INSTALL")
        set(args install)
      endif()
      if(step STREQUAL "TEST")
        set(args test)
      endif()
    endif()

    # Use user-specified arguments instead of default arguments, if any.
    get_property(have_args TARGET ${name} PROPERTY _EP_${step}_ARGS SET)
    if(have_args)
      get_target_property(args ${name} _EP_${step}_ARGS)
    endif()

    list(APPEND cmd ${args})
  endif()

  set(${cmd_var} "${cmd}" PARENT_SCOPE)
endfunction()

function(_ep_write_log_script name step cmd_var)
  ExternalProject_Get_Property(${name} stamp_dir)
  set(command "${${cmd_var}}")

  set(make "")
  set(code_cygpath_make "")
  if("${command}" MATCHES "^\\$\\(MAKE\\)")
    # GNU make recognizes the string "$(MAKE)" as recursive make, so
    # ensure that it appears directly in the makefile.
    string(REGEX REPLACE "^\\$\\(MAKE\\)" "\${make}" command "${command}")
    set(make "-Dmake=$(MAKE)")

    if(WIN32 AND NOT CYGWIN)
      set(code_cygpath_make "
if(\${make} MATCHES \"^/\")
  execute_process(
    COMMAND cygpath -w \${make}
    OUTPUT_VARIABLE cygpath_make
    ERROR_VARIABLE cygpath_make
    RESULT_VARIABLE cygpath_error
    OUTPUT_STRIP_TRAILING_WHITESPACE
  )
  if(NOT cygpath_error)
    set(make \${cygpath_make})
  endif()
endif()
")
    endif()
  endif()

  set(config "")
  if("${CMAKE_CFG_INTDIR}" MATCHES "^\\$")
    string(REPLACE "${CMAKE_CFG_INTDIR}" "\${config}" command "${command}")
    set(config "-Dconfig=${CMAKE_CFG_INTDIR}")
  endif()

  # Wrap multiple 'COMMAND' lines up into a second-level wrapper
  # script so all output can be sent to one log file.
  if("${command}" MATCHES ";COMMAND;")
    set(code_execute_process "
${code_cygpath_make}
execute_process(COMMAND \${command} RESULT_VARIABLE result)
if(result)
  set(msg \"Command failed (\${result}):\\n\")
  foreach(arg IN LISTS command)
    set(msg \"\${msg} '\${arg}'\")
  endforeach()
  message(FATAL_ERROR \"\${msg}\")
endif()
")
    set(code "")
    set(cmd "")
    set(sep "")
    foreach(arg IN LISTS command)
      if("x${arg}" STREQUAL "xCOMMAND")
        set(code "${code}set(command \"${cmd}\")${code_execute_process}")
        set(cmd "")
        set(sep "")
      else()
        set(cmd "${cmd}${sep}${arg}")
        set(sep ";")
      endif()
    endforeach()
    set(code "set(ENV{VS_UNICODE_OUTPUT} \"\")\n${code}set(command \"${cmd}\")${code_execute_process}")
    file(WRITE ${stamp_dir}/${name}-${step}-impl.cmake "${code}")
    set(command ${CMAKE_COMMAND} "-Dmake=\${make}" "-Dconfig=\${config}" -P ${stamp_dir}/${name}-${step}-impl.cmake)
  endif()

  # Wrap the command in a script to log output to files.
  set(script ${stamp_dir}/${name}-${step}.cmake)
  set(logbase ${stamp_dir}/${name}-${step})
  file(WRITE ${script} "
${code_cygpath_make}
set(ENV{VS_UNICODE_OUTPUT} \"\")
set(command \"${command}\")
execute_process(
  COMMAND \${command}
  RESULT_VARIABLE result
  OUTPUT_FILE \"${logbase}-out.log\"
  ERROR_FILE \"${logbase}-err.log\"
  )
if(result)
  set(msg \"Command failed: \${result}\\n\")
  foreach(arg IN LISTS command)
    set(msg \"\${msg} '\${arg}'\")
  endforeach()
  set(msg \"\${msg}\\nSee also\\n  ${logbase}-*.log\\n\")
  message(FATAL_ERROR \"\${msg}\")
else()
  set(msg \"${name} ${step} command succeeded.  See also ${logbase}-*.log\\n\")
  message(STATUS \"\${msg}\")
endif()
")
  set(command ${CMAKE_COMMAND} ${make} ${config} -P ${script})
  set(${cmd_var} "${command}" PARENT_SCOPE)
endfunction()

# This module used to use "/${CMAKE_CFG_INTDIR}" directly and produced
# makefiles with "/./" in paths for custom command dependencies. Which
# resulted in problems with parallel make -j invocations.
#
# This function was added so that the suffix (search below for ${cfgdir}) is
# only set to "/${CMAKE_CFG_INTDIR}" when ${CMAKE_CFG_INTDIR} is not going to
# be "." (multi-configuration build systems like Visual Studio and Xcode...)
#
function(_ep_get_configuration_subdir_suffix suffix_var)
  set(suffix "")
  if(CMAKE_CONFIGURATION_TYPES)
    set(suffix "/${CMAKE_CFG_INTDIR}")
  endif()
  set(${suffix_var} "${suffix}" PARENT_SCOPE)
endfunction()


function(_ep_get_step_stampfile name step stampfile_var)
  ExternalProject_Get_Property(${name} stamp_dir)

  _ep_get_configuration_subdir_suffix(cfgdir)
  set(stampfile "${stamp_dir}${cfgdir}/${name}-${step}")

  set(${stampfile_var} "${stampfile}" PARENT_SCOPE)
endfunction()


function(ExternalProject_Add_StepTargets name)
  set(steps ${ARGN})

  foreach(step ${steps})
    _ep_get_step_stampfile(${name} ${step} stamp_file)
    add_custom_target(${name}-${step}
      DEPENDS ${stamp_file})

    # Depend on other external projects (target-level).
    get_property(deps TARGET ${name} PROPERTY _EP_DEPENDS)
    foreach(arg IN LISTS deps)
      add_dependencies(${name}-${step} ${arg})
    endforeach()
  endforeach()
endfunction()


function(ExternalProject_Add_Step name step)
  set(cmf_dir ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles)
  _ep_get_configuration_subdir_suffix(cfgdir)

  set(complete_stamp_file "${cmf_dir}${cfgdir}/${name}-complete")
  _ep_get_step_stampfile(${name} ${step} stamp_file)

  add_custom_command(APPEND
    OUTPUT ${complete_stamp_file}
    DEPENDS ${stamp_file}
    )

  _ep_parse_arguments(ExternalProject_Add_Step
                      ${name} _EP_${step}_ "${ARGN}")

  # Steps depending on this step.
  get_property(dependers TARGET ${name} PROPERTY _EP_${step}_DEPENDERS)
  foreach(depender IN LISTS dependers)
    _ep_get_step_stampfile(${name} ${depender} depender_stamp_file)
    add_custom_command(APPEND
      OUTPUT ${depender_stamp_file}
      DEPENDS ${stamp_file}
      )
  endforeach()

  # Dependencies on files.
  get_property(depends TARGET ${name} PROPERTY _EP_${step}_DEPENDS)

  # Dependencies on steps.
  get_property(dependees TARGET ${name} PROPERTY _EP_${step}_DEPENDEES)
  foreach(dependee IN LISTS dependees)
    _ep_get_step_stampfile(${name} ${dependee} dependee_stamp_file)
    list(APPEND depends ${dependee_stamp_file})
  endforeach()

  # The command to run.
  get_property(command TARGET ${name} PROPERTY _EP_${step}_COMMAND)
  if(command)
    set(comment "Performing ${step} step for '${name}'")
  else()
    set(comment "No ${step} step for '${name}'")
  endif()
  get_property(work_dir TARGET ${name} PROPERTY _EP_${step}_WORKING_DIRECTORY)

  # Replace list separators.
  get_property(sep TARGET ${name} PROPERTY _EP_LIST_SEPARATOR)
  if(sep AND command)
    string(REPLACE "${sep}" "\\;" command "${command}")
  endif()

  # Replace location tags.
  _ep_replace_location_tags(${name} comment command work_dir)

  # Custom comment?
  get_property(comment_set TARGET ${name} PROPERTY _EP_${step}_COMMENT SET)
  if(comment_set)
    get_property(comment TARGET ${name} PROPERTY _EP_${step}_COMMENT)
  endif()

  # Run every time?
  get_property(always TARGET ${name} PROPERTY _EP_${step}_ALWAYS)
  if(always)
    set_property(SOURCE ${stamp_file} PROPERTY SYMBOLIC 1)
    set(touch)
  else()
    set(touch ${CMAKE_COMMAND} -E touch ${stamp_file})
  endif()

  # Wrap with log script?
  get_property(log TARGET ${name} PROPERTY _EP_${step}_LOG)
  if(command AND log)
    _ep_write_log_script(${name} ${step} command)
  endif()

  add_custom_command(
    OUTPUT ${stamp_file}
    COMMENT ${comment}
    COMMAND ${command}
    COMMAND ${touch}
    DEPENDS ${depends}
    WORKING_DIRECTORY ${work_dir}
    VERBATIM
    )

  # Add custom "step target"?
  get_property(step_targets TARGET ${name} PROPERTY _EP_STEP_TARGETS)
  if(NOT step_targets)
    get_property(step_targets DIRECTORY PROPERTY EP_STEP_TARGETS)
  endif()
  foreach(st ${step_targets})
    if("${st}" STREQUAL "${step}")
      ExternalProject_Add_StepTargets(${name} ${step})
      break()
    endif()
  endforeach()
endfunction()


function(_ep_add_mkdir_command name)
  ExternalProject_Get_Property(${name}
    source_dir binary_dir install_dir stamp_dir download_dir tmp_dir)

  _ep_get_configuration_subdir_suffix(cfgdir)

  ExternalProject_Add_Step(${name} mkdir
    COMMENT "Creating directories for '${name}'"
    COMMAND ${CMAKE_COMMAND} -E make_directory ${source_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${binary_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${install_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${tmp_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${stamp_dir}${cfgdir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${download_dir}
    )
endfunction()


function(_ep_get_git_version git_EXECUTABLE git_version_var)
  if(git_EXECUTABLE)
    execute_process(
      COMMAND "${git_EXECUTABLE}" --version
      OUTPUT_VARIABLE ov
      ERROR_VARIABLE ev
      OUTPUT_STRIP_TRAILING_WHITESPACE
      )
    string(REGEX REPLACE "^git version (.+)$" "\\1" version "${ov}")
    set(${git_version_var} "${version}" PARENT_SCOPE)
  endif()
endfunction()


function(_ep_is_dir_empty dir empty_var)
  file(GLOB gr "${dir}/*")
  if("${gr}" STREQUAL "")
    set(${empty_var} 1 PARENT_SCOPE)
  else()
    set(${empty_var} 0 PARENT_SCOPE)
  endif()
endfunction()


function(_ep_add_download_command name)
  ExternalProject_Get_Property(${name} source_dir stamp_dir download_dir tmp_dir)

  get_property(cmd_set TARGET ${name} PROPERTY _EP_DOWNLOAD_COMMAND SET)
  get_property(cmd TARGET ${name} PROPERTY _EP_DOWNLOAD_COMMAND)
  get_property(cvs_repository TARGET ${name} PROPERTY _EP_CVS_REPOSITORY)
  get_property(svn_repository TARGET ${name} PROPERTY _EP_SVN_REPOSITORY)
  get_property(git_repository TARGET ${name} PROPERTY _EP_GIT_REPOSITORY)
  get_property(hg_repository  TARGET ${name} PROPERTY _EP_HG_REPOSITORY )
  get_property(url TARGET ${name} PROPERTY _EP_URL)

  # TODO: Perhaps file:// should be copied to download dir before extraction.
  string(REGEX REPLACE "^file://" "" url "${url}")

  set(depends)
  set(comment)
  set(work_dir)

  if(cmd_set)
    set(work_dir ${download_dir})
  elseif(cvs_repository)
    find_package(CVS)
    if(NOT CVS_EXECUTABLE)
      message(FATAL_ERROR "error: could not find cvs for checkout of ${name}")
    endif()

    get_target_property(cvs_module ${name} _EP_CVS_MODULE)
    if(NOT cvs_module)
      message(FATAL_ERROR "error: no CVS_MODULE")
    endif()

    get_property(cvs_tag TARGET ${name} PROPERTY _EP_CVS_TAG)

    set(repository ${cvs_repository})
    set(module ${cvs_module})
    set(tag ${cvs_tag})
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-cvsinfo.txt"
      @ONLY
      )

    get_filename_component(src_name "${source_dir}" NAME)
    get_filename_component(work_dir "${source_dir}" PATH)
    set(comment "Performing download step (CVS checkout) for '${name}'")
    set(cmd ${CVS_EXECUTABLE} -d ${cvs_repository} -q co ${cvs_tag} -d ${src_name} ${cvs_module})
    list(APPEND depends ${stamp_dir}/${name}-cvsinfo.txt)
  elseif(svn_repository)
    find_package(Subversion)
    if(NOT Subversion_SVN_EXECUTABLE)
      message(FATAL_ERROR "error: could not find svn for checkout of ${name}")
    endif()

    get_property(svn_revision TARGET ${name} PROPERTY _EP_SVN_REVISION)
    get_property(svn_username TARGET ${name} PROPERTY _EP_SVN_USERNAME)
    get_property(svn_password TARGET ${name} PROPERTY _EP_SVN_PASSWORD)
    get_property(svn_trust_cert TARGET ${name} PROPERTY _EP_SVN_TRUST_CERT)

    set(repository "${svn_repository} user=${svn_username} password=${svn_password}")
    set(module)
    set(tag ${svn_revision})
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-svninfo.txt"
      @ONLY
      )

    get_filename_component(src_name "${source_dir}" NAME)
    get_filename_component(work_dir "${source_dir}" PATH)
    set(comment "Performing download step (SVN checkout) for '${name}'")
    set(svn_user_pw_args "")
    if(svn_username)
      set(svn_user_pw_args ${svn_user_pw_args} "--username=${svn_username}")
    endif()
    if(svn_password)
      set(svn_user_pw_args ${svn_user_pw_args} "--password=${svn_password}")
    endif()
    if(svn_trust_cert)
      set(svn_trust_cert_args --trust-server-cert)
    endif()
    set(cmd ${Subversion_SVN_EXECUTABLE} co ${svn_repository} ${svn_revision}
      --non-interactive ${svn_trust_cert_args} ${svn_user_pw_args} ${src_name})
    list(APPEND depends ${stamp_dir}/${name}-svninfo.txt)
  elseif(git_repository)
    find_package(Git)
    if(NOT GIT_EXECUTABLE)
      message(FATAL_ERROR "error: could not find git for clone of ${name}")
    endif()

    # The git submodule update '--recursive' flag requires git >= v1.6.5
    #
    _ep_get_git_version("${GIT_EXECUTABLE}" git_version)
    if(git_version VERSION_LESS 1.6.5)
      message(FATAL_ERROR "error: git version 1.6.5 or later required for 'git submodule update --recursive': git_version='${git_version}'")
    endif()

    get_property(git_tag TARGET ${name} PROPERTY _EP_GIT_TAG)
    if(NOT git_tag)
      set(git_tag "master")
    endif()

    # For the download step, and the git clone operation, only the repository
    # should be recorded in a configured RepositoryInfo file. If the repo
    # changes, the clone script should be run again. But if only the tag
    # changes, avoid running the clone script again. Let the 'always' running
    # update step checkout the new tag.
    #
    set(repository ${git_repository})
    set(module)
    set(tag)
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-gitinfo.txt"
      @ONLY
      )

    get_filename_component(src_name "${source_dir}" NAME)
    get_filename_component(work_dir "${source_dir}" PATH)

    # Since git clone doesn't succeed if the non-empty source_dir exists,
    # create a cmake script to invoke as download command.
    # The script will delete the source directory and then call git clone.
    #
    _ep_write_gitclone_script(${tmp_dir}/${name}-gitclone.cmake ${source_dir}
      ${GIT_EXECUTABLE} ${git_repository} ${git_tag} ${src_name} ${work_dir}
      ${stamp_dir}/${name}-gitinfo.txt ${stamp_dir}/${name}-gitclone-lastrun.txt
      )
    set(comment "Performing download step (git clone) for '${name}'")
    set(cmd ${CMAKE_COMMAND} -P ${tmp_dir}/${name}-gitclone.cmake)
    list(APPEND depends ${stamp_dir}/${name}-gitinfo.txt)
  elseif(hg_repository)
    find_package(Hg)
    if(NOT HG_EXECUTABLE)
      message(FATAL_ERROR "error: could not find hg for clone of ${name}")
    endif()

    get_property(hg_tag TARGET ${name} PROPERTY _EP_HG_TAG)
    if(NOT hg_tag)
      set(hg_tag "tip")
    endif()

    # For the download step, and the hg clone operation, only the repository
    # should be recorded in a configured RepositoryInfo file. If the repo
    # changes, the clone script should be run again. But if only the tag
    # changes, avoid running the clone script again. Let the 'always' running
    # update step checkout the new tag.
    #
    set(repository ${hg_repository})
    set(module)
    set(tag)
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-hginfo.txt"
      @ONLY
      )

    get_filename_component(src_name "${source_dir}" NAME)
    get_filename_component(work_dir "${source_dir}" PATH)

    # Since hg clone doesn't succeed if the non-empty source_dir exists,
    # create a cmake script to invoke as download command.
    # The script will delete the source directory and then call hg clone.
    #
    _ep_write_hgclone_script(${tmp_dir}/${name}-hgclone.cmake ${source_dir}
      ${HG_EXECUTABLE} ${hg_repository} ${hg_tag} ${src_name} ${work_dir}
      ${stamp_dir}/${name}-hginfo.txt ${stamp_dir}/${name}-hgclone-lastrun.txt
      )
    set(comment "Performing download step (hg clone) for '${name}'")
    set(cmd ${CMAKE_COMMAND} -P ${tmp_dir}/${name}-hgclone.cmake)
    list(APPEND depends ${stamp_dir}/${name}-hginfo.txt)
  elseif(url)
    get_filename_component(work_dir "${source_dir}" PATH)
    get_property(hash TARGET ${name} PROPERTY _EP_URL_HASH)
    if(hash AND NOT "${hash}" MATCHES "${_ep_hash_regex}")
      message(FATAL_ERROR "URL_HASH is set to\n  ${hash}\n"
        "but must be ALGO=value where ALGO is\n  ${_ep_hash_algos}\n"
        "and value is a hex string.")
    endif()
    get_property(md5 TARGET ${name} PROPERTY _EP_URL_MD5)
    if(md5 AND NOT "MD5=${md5}" MATCHES "${_ep_hash_regex}")
      message(FATAL_ERROR "URL_MD5 is set to\n  ${md5}\nbut must be a hex string.")
    endif()
    if(md5 AND NOT hash)
      set(hash "MD5=${md5}")
    endif()
    set(repository "external project URL")
    set(module "${url}")
    set(tag "${hash}")
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-urlinfo.txt"
      @ONLY
      )
    list(APPEND depends ${stamp_dir}/${name}-urlinfo.txt)
    if(IS_DIRECTORY "${url}")
      get_filename_component(abs_dir "${url}" ABSOLUTE)
      set(comment "Performing download step (DIR copy) for '${name}'")
      set(cmd   ${CMAKE_COMMAND} -E remove_directory ${source_dir}
        COMMAND ${CMAKE_COMMAND} -E copy_directory ${abs_dir} ${source_dir})
    else()
      if("${url}" MATCHES "^[a-z]+://")
        # TODO: Should download and extraction be different steps?
        string(REGEX MATCH "[^/\\?]*$" fname "${url}")
        if(NOT "${fname}" MATCHES "(\\.|=)(bz2|tar|tgz|tar\\.gz|zip)$")
          string(REGEX MATCH "([^/\\?]+(\\.|=)(bz2|tar|tgz|tar\\.gz|zip))/.*$" match_result "${url}")
          set(fname "${CMAKE_MATCH_1}")
        endif()
        if(NOT "${fname}" MATCHES "(\\.|=)(bz2|tar|tgz|tar\\.gz|zip)$")
          message(FATAL_ERROR "Could not extract tarball filename from url:\n  ${url}")
        endif()
        string(REPLACE ";" "-" fname "${fname}")
        set(file ${download_dir}/${fname})
        get_property(timeout TARGET ${name} PROPERTY _EP_TIMEOUT)
        get_property(ssl_verify TARGET ${name} PROPERTY _EP_SSL_VERIFYPEER)
        get_property(cainfo_file TARGET ${name} PROPERTY _EP_CAINFO_FILE)
        _ep_write_downloadfile_script("${stamp_dir}/download-${name}.cmake"
          "${url}" "${file}" "${timeout}" "${hash}" "${ssl_verify}" "${cainfo_file}")
        set(cmd ${CMAKE_COMMAND} -P ${stamp_dir}/download-${name}.cmake
          COMMAND)
        set(comment "Performing download step (download, verify and extract) for '${name}'")
      else()
        set(file "${url}")
        set(comment "Performing download step (verify and extract) for '${name}'")
      endif()
      _ep_write_verifyfile_script("${stamp_dir}/verify-${name}.cmake" "${file}" "${hash}")
      list(APPEND cmd ${CMAKE_COMMAND} -P ${stamp_dir}/verify-${name}.cmake
        COMMAND)
      _ep_write_extractfile_script("${stamp_dir}/extract-${name}.cmake" "${name}" "${file}" "${source_dir}")
      list(APPEND cmd ${CMAKE_COMMAND} -P ${stamp_dir}/extract-${name}.cmake)
    endif()
  else()
    _ep_is_dir_empty("${source_dir}" empty)
    if(${empty})
      message(SEND_ERROR "error: no download info for '${name}' -- please specify existing/non-empty SOURCE_DIR or one of URL, CVS_REPOSITORY and CVS_MODULE, SVN_REPOSITORY, GIT_REPOSITORY, HG_REPOSITORY or DOWNLOAD_COMMAND")
    endif()
  endif()

  get_property(log TARGET ${name} PROPERTY _EP_LOG_DOWNLOAD)
  if(log)
    set(log LOG 1)
  else()
    set(log "")
  endif()

  ExternalProject_Add_Step(${name} download
    COMMENT ${comment}
    COMMAND ${cmd}
    WORKING_DIRECTORY ${work_dir}
    DEPENDS ${depends}
    DEPENDEES mkdir
    ${log}
    )
endfunction()


function(_ep_add_update_command name)
  ExternalProject_Get_Property(${name} source_dir)

  get_property(cmd_set TARGET ${name} PROPERTY _EP_UPDATE_COMMAND SET)
  get_property(cmd TARGET ${name} PROPERTY _EP_UPDATE_COMMAND)
  get_property(cvs_repository TARGET ${name} PROPERTY _EP_CVS_REPOSITORY)
  get_property(svn_repository TARGET ${name} PROPERTY _EP_SVN_REPOSITORY)
  get_property(git_repository TARGET ${name} PROPERTY _EP_GIT_REPOSITORY)
  get_property(hg_repository  TARGET ${name} PROPERTY _EP_HG_REPOSITORY )

  set(work_dir)
  set(comment)
  set(always)

  if(cmd_set)
    set(work_dir ${source_dir})
  elseif(cvs_repository)
    if(NOT CVS_EXECUTABLE)
      message(FATAL_ERROR "error: could not find cvs for update of ${name}")
    endif()
    set(work_dir ${source_dir})
    set(comment "Performing update step (CVS update) for '${name}'")
    get_property(cvs_tag TARGET ${name} PROPERTY _EP_CVS_TAG)
    set(cmd ${CVS_EXECUTABLE} -d ${cvs_repository} -q up -dP ${cvs_tag})
    set(always 1)
  elseif(svn_repository)
    if(NOT Subversion_SVN_EXECUTABLE)
      message(FATAL_ERROR "error: could not find svn for update of ${name}")
    endif()
    set(work_dir ${source_dir})
    set(comment "Performing update step (SVN update) for '${name}'")
    get_property(svn_revision TARGET ${name} PROPERTY _EP_SVN_REVISION)
    get_property(svn_username TARGET ${name} PROPERTY _EP_SVN_USERNAME)
    get_property(svn_password TARGET ${name} PROPERTY _EP_SVN_PASSWORD)
    get_property(svn_trust_cert TARGET ${name} PROPERTY _EP_SVN_TRUST_CERT)
    set(svn_user_pw_args "")
    if(svn_username)
      set(svn_user_pw_args ${svn_user_pw_args} "--username=${svn_username}")
    endif()
    if(svn_password)
      set(svn_user_pw_args ${svn_user_pw_args} "--password=${svn_password}")
    endif()
    if(svn_trust_cert)
      set(svn_trust_cert_args --trust-server-cert)
    endif()
    set(cmd ${Subversion_SVN_EXECUTABLE} up ${svn_revision}
      --non-interactive ${svn_trust_cert_args} ${svn_user_pw_args})
    set(always 1)
  elseif(git_repository)
    if(NOT GIT_EXECUTABLE)
      message(FATAL_ERROR "error: could not find git for fetch of ${name}")
    endif()
    set(work_dir ${source_dir})
    set(comment "Performing update step (git fetch) for '${name}'")
    get_property(git_tag TARGET ${name} PROPERTY _EP_GIT_TAG)
    if(NOT git_tag)
      set(git_tag "master")
    endif()
    set(cmd ${GIT_EXECUTABLE} fetch
      COMMAND ${GIT_EXECUTABLE} checkout ${git_tag}
      COMMAND ${GIT_EXECUTABLE} submodule update --recursive
      )
    set(always 1)
  elseif(hg_repository)
    if(NOT HG_EXECUTABLE)
      message(FATAL_ERROR "error: could not find hg for pull of ${name}")
    endif()
    set(work_dir ${source_dir})
    set(comment "Performing update step (hg pull) for '${name}'")
    get_property(hg_tag TARGET ${name} PROPERTY _EP_HG_TAG)
    if(NOT hg_tag)
      set(hg_tag "tip")
    endif()
    if("${HG_VERSION_STRING}" STREQUAL "2.1")
      message(WARNING "Mercurial 2.1 does not distinguish an empty pull from a failed pull:
 http://mercurial.selenic.com/wiki/UpgradeNotes#A2.1.1:_revert_pull_return_code_change.2C_compile_issue_on_OS_X
 http://thread.gmane.org/gmane.comp.version-control.mercurial.devel/47656
Update to Mercurial >= 2.1.1.
")
    endif()
    set(cmd ${HG_EXECUTABLE} pull
      COMMAND ${HG_EXECUTABLE} update ${hg_tag}
      )
    set(always 1)
  endif()

  get_property(log TARGET ${name} PROPERTY _EP_LOG_UPDATE)
  if(log)
    set(log LOG 1)
  else()
    set(log "")
  endif()

  ExternalProject_Add_Step(${name} update
    COMMENT ${comment}
    COMMAND ${cmd}
    ALWAYS ${always}
    WORKING_DIRECTORY ${work_dir}
    DEPENDEES download
    ${log}
    )
endfunction()


function(_ep_add_patch_command name)
  ExternalProject_Get_Property(${name} source_dir)

  get_property(cmd_set TARGET ${name} PROPERTY _EP_PATCH_COMMAND SET)
  get_property(cmd TARGET ${name} PROPERTY _EP_PATCH_COMMAND)

  set(work_dir)

  if(cmd_set)
    set(work_dir ${source_dir})
  endif()

  ExternalProject_Add_Step(${name} patch
    COMMAND ${cmd}
    WORKING_DIRECTORY ${work_dir}
    DEPENDEES download
    )
endfunction()


# TODO: Make sure external projects use the proper compiler
function(_ep_add_configure_command name)
  ExternalProject_Get_Property(${name} source_dir binary_dir tmp_dir)

  # Depend on other external projects (file-level).
  set(file_deps)
  get_property(deps TARGET ${name} PROPERTY _EP_DEPENDS)
  foreach(dep IN LISTS deps)
    _ep_get_step_stampfile(${dep} "done" done_stamp_file)
    list(APPEND file_deps ${done_stamp_file})
  endforeach()

  get_property(cmd_set TARGET ${name} PROPERTY _EP_CONFIGURE_COMMAND SET)
  if(cmd_set)
    get_property(cmd TARGET ${name} PROPERTY _EP_CONFIGURE_COMMAND)
  else()
    get_target_property(cmake_command ${name} _EP_CMAKE_COMMAND)
    if(cmake_command)
      set(cmd "${cmake_command}")
    else()
      set(cmd "${CMAKE_COMMAND}")
    endif()

    get_property(cmake_args TARGET ${name} PROPERTY _EP_CMAKE_ARGS)
    list(APPEND cmd ${cmake_args})

    # If there are any CMAKE_CACHE_ARGS, write an initial cache and use it
    get_property(cmake_cache_args TARGET ${name} PROPERTY _EP_CMAKE_CACHE_ARGS)
    if(cmake_cache_args)
      set(_ep_cache_args_script "${tmp_dir}/${name}-cache.cmake")
      _ep_write_initial_cache(${name} "${_ep_cache_args_script}" "${cmake_cache_args}")
      list(APPEND cmd "-C${_ep_cache_args_script}")
    endif()

    get_target_property(cmake_generator ${name} _EP_CMAKE_GENERATOR)
    if(cmake_generator)
      list(APPEND cmd "-G${cmake_generator}" "${source_dir}")
    else()
      if(CMAKE_EXTRA_GENERATOR)
        list(APPEND cmd "-G${CMAKE_EXTRA_GENERATOR} - ${CMAKE_GENERATOR}"
          "${source_dir}")
      else()
        list(APPEND cmd "-G${CMAKE_GENERATOR}" "${source_dir}")
      endif()
    endif()
  endif()

  # If anything about the configure command changes, (command itself, cmake
  # used, cmake args or cmake generator) then re-run the configure step.
  # Fixes issue http://public.kitware.com/Bug/view.php?id=10258
  #
  if(NOT EXISTS ${tmp_dir}/${name}-cfgcmd.txt.in)
    file(WRITE ${tmp_dir}/${name}-cfgcmd.txt.in "cmd='\@cmd\@'\n")
  endif()
  configure_file(${tmp_dir}/${name}-cfgcmd.txt.in ${tmp_dir}/${name}-cfgcmd.txt)
  list(APPEND file_deps ${tmp_dir}/${name}-cfgcmd.txt)
  list(APPEND file_deps ${_ep_cache_args_script})

  get_property(log TARGET ${name} PROPERTY _EP_LOG_CONFIGURE)
  if(log)
    set(log LOG 1)
  else()
    set(log "")
  endif()

  ExternalProject_Add_Step(${name} configure
    COMMAND ${cmd}
    WORKING_DIRECTORY ${binary_dir}
    DEPENDEES update patch
    DEPENDS ${file_deps}
    ${log}
    )
endfunction()


function(_ep_add_build_command name)
  ExternalProject_Get_Property(${name} binary_dir)

  get_property(cmd_set TARGET ${name} PROPERTY _EP_BUILD_COMMAND SET)
  if(cmd_set)
    get_property(cmd TARGET ${name} PROPERTY _EP_BUILD_COMMAND)
  else()
    _ep_get_build_command(${name} BUILD cmd)
  endif()

  get_property(log TARGET ${name} PROPERTY _EP_LOG_BUILD)
  if(log)
    set(log LOG 1)
  else()
    set(log "")
  endif()

  ExternalProject_Add_Step(${name} build
    COMMAND ${cmd}
    WORKING_DIRECTORY ${binary_dir}
    DEPENDEES configure
    ${log}
    )
endfunction()


function(_ep_add_install_command name)
  ExternalProject_Get_Property(${name} binary_dir)

  get_property(cmd_set TARGET ${name} PROPERTY _EP_INSTALL_COMMAND SET)
  if(cmd_set)
    get_property(cmd TARGET ${name} PROPERTY _EP_INSTALL_COMMAND)
  else()
    _ep_get_build_command(${name} INSTALL cmd)
  endif()

  get_property(log TARGET ${name} PROPERTY _EP_LOG_INSTALL)
  if(log)
    set(log LOG 1)
  else()
    set(log "")
  endif()

  ExternalProject_Add_Step(${name} install
    COMMAND ${cmd}
    WORKING_DIRECTORY ${binary_dir}
    DEPENDEES build
    ${log}
    )
endfunction()


function(_ep_add_test_command name)
  ExternalProject_Get_Property(${name} binary_dir)

  get_property(before TARGET ${name} PROPERTY _EP_TEST_BEFORE_INSTALL)
  get_property(after TARGET ${name} PROPERTY _EP_TEST_AFTER_INSTALL)
  get_property(cmd_set TARGET ${name} PROPERTY _EP_TEST_COMMAND SET)

  # Only actually add the test step if one of the test related properties is
  # explicitly set. (i.e. the test step is omitted unless requested...)
  #
  if(cmd_set OR before OR after)
    if(cmd_set)
      get_property(cmd TARGET ${name} PROPERTY _EP_TEST_COMMAND)
    else()
      _ep_get_build_command(${name} TEST cmd)
    endif()

    if(before)
      set(dep_args DEPENDEES build DEPENDERS install)
    else()
      set(dep_args DEPENDEES install)
    endif()

    get_property(log TARGET ${name} PROPERTY _EP_LOG_TEST)
    if(log)
      set(log LOG 1)
    else()
      set(log "")
    endif()

    ExternalProject_Add_Step(${name} test
      COMMAND ${cmd}
      WORKING_DIRECTORY ${binary_dir}
      ${dep_args}
      ${log}
      )
  endif()
endfunction()


function(ExternalProject_Add name)
  _ep_get_configuration_subdir_suffix(cfgdir)

  # Add a custom target for the external project.
  set(cmf_dir ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles)
  set(complete_stamp_file "${cmf_dir}${cfgdir}/${name}-complete")

  add_custom_target(${name} ALL DEPENDS ${complete_stamp_file})
  set_property(TARGET ${name} PROPERTY _EP_IS_EXTERNAL_PROJECT 1)
  _ep_parse_arguments(ExternalProject_Add ${name} _EP_ "${ARGN}")
  _ep_set_directories(${name})
  _ep_get_step_stampfile(${name} "done" done_stamp_file)
  _ep_get_step_stampfile(${name} "install" install_stamp_file)

  # The 'complete' step depends on all other steps and creates a
  # 'done' mark.  A dependent external project's 'configure' step
  # depends on the 'done' mark so that it rebuilds when this project
  # rebuilds.  It is important that 'done' is not the output of any
  # custom command so that CMake does not propagate build rules to
  # other external project targets, which may cause problems during
  # parallel builds.  However, the Ninja generator needs to see the entire
  # dependency graph, and can cope with custom commands belonging to
  # multiple targets, so we add the 'done' mark as an output for Ninja only.
  set(complete_outputs ${complete_stamp_file})
  if(${CMAKE_GENERATOR} MATCHES "Ninja")
    set(complete_outputs ${complete_outputs} ${done_stamp_file})
  endif()

  add_custom_command(
    OUTPUT ${complete_outputs}
    COMMENT "Completed '${name}'"
    COMMAND ${CMAKE_COMMAND} -E make_directory ${cmf_dir}${cfgdir}
    COMMAND ${CMAKE_COMMAND} -E touch ${complete_stamp_file}
    COMMAND ${CMAKE_COMMAND} -E touch ${done_stamp_file}
    DEPENDS ${install_stamp_file}
    VERBATIM
    )


  # Depend on other external projects (target-level).
  get_property(deps TARGET ${name} PROPERTY _EP_DEPENDS)
  foreach(arg IN LISTS deps)
    add_dependencies(${name} ${arg})
  endforeach()

  # Set up custom build steps based on the target properties.
  # Each step depends on the previous one.
  #
  # The target depends on the output of the final step.
  # (Already set up above in the DEPENDS of the add_custom_target command.)
  #
  _ep_add_mkdir_command(${name})
  _ep_add_download_command(${name})
  _ep_add_update_command(${name})
  _ep_add_patch_command(${name})
  _ep_add_configure_command(${name})
  _ep_add_build_command(${name})
  _ep_add_install_command(${name})

  # Test is special in that it might depend on build, or it might depend
  # on install.
  #
  _ep_add_test_command(${name})
endfunction()