CMakeLists.txt

#
# Copyright 2017 The Abseil Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

# Most widely used distributions have cmake 3.5 or greater available as of March
# 2019.  A notable exception is RHEL-7 (CentOS7).  You can install a current
# version of CMake by first installing Extra Packages for Enterprise Linux
# (https://fedoraproject.org/wiki/EPEL#Extra_Packages_for_Enterprise_Linux_.28EPEL.29)
# and then issuing `yum install cmake3` on the command line.
cmake_minimum_required(VERSION 3.5)

# Compiler id for Apple Clang is now AppleClang.
if (POLICY CMP0025)
  cmake_policy(SET CMP0025 NEW)
endif (POLICY CMP0025)

# if command can use IN_LIST
if (POLICY CMP0057)
  cmake_policy(SET CMP0057 NEW)
endif (POLICY CMP0057)

# Project version variables are the empty string if version is unspecified
if (POLICY CMP0048)
  cmake_policy(SET CMP0048 NEW)
endif (POLICY CMP0048)

# option() honor variables
if (POLICY CMP0077)
  cmake_policy(SET CMP0077 NEW)
endif (POLICY CMP0077)

project(absl CXX)

# Output directory is correct by default for most build setups. However, when
# building Abseil as a DLL, it is important to have the DLL in the same
# directory as the executable using it. Thus, we put all executables in a single
# /bin directory.
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)

# when absl is included as subproject (i.e. using add_subdirectory(abseil-cpp))
# in the source tree of a project that uses it, install rules are disabled.
if(NOT CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
  option(ABSL_ENABLE_INSTALL "Enable install rule" OFF)
else()
  option(ABSL_ENABLE_INSTALL "Enable install rule" ON)
endif()

list(APPEND CMAKE_MODULE_PATH
  ${CMAKE_CURRENT_LIST_DIR}/CMake
  ${CMAKE_CURRENT_LIST_DIR}/absl/copts
)

include(AbseilInstallDirs)
include(CMakePackageConfigHelpers)
include(AbseilDll)
include(AbseilHelpers)


##
## Using absl targets
##
## all public absl targets are
## exported with the absl:: prefix
##
## e.g absl::base absl::synchronization absl::strings ....
##
## DO NOT rely on the internal targets outside of the prefix


# include current path
list(APPEND ABSL_COMMON_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR})

if("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
  set(ABSL_USING_CLANG ON)
else()
  set(ABSL_USING_CLANG OFF)
endif()

# find dependencies
## pthread
find_package(Threads REQUIRED)

option(ABSL_USE_EXTERNAL_GOOGLETEST
  "If ON, Abseil will assume that the targets for GoogleTest are already provided by the including project. This makes sense when Abseil is used with add_subproject." OFF)

option(ABSL_USE_GOOGLETEST_HEAD
  "If ON, abseil will download HEAD from GoogleTest at config time." OFF)

set(ABSL_GOOGLETEST_DOWNLOAD_URL "" CACHE STRING "If set, download GoogleTest from this URL")

set(ABSL_LOCAL_GOOGLETEST_DIR "/usr/src/googletest" CACHE PATH
  "If ABSL_USE_GOOGLETEST_HEAD is OFF and ABSL_GOOGLETEST_URL is not set, specifies the directory of a local GoogleTest checkout."
  )

option(ABSL_RUN_TESTS "If ON, Abseil tests will be run." OFF)

if(${ABSL_RUN_TESTS})
  # enable CTest.  This will set BUILD_TESTING to ON unless otherwise specified
  # on the command line
  include(CTest)

  ## check targets
  if (NOT ABSL_USE_EXTERNAL_GOOGLETEST)
    set(absl_gtest_build_dir ${CMAKE_BINARY_DIR}/googletest-build)
    if(ABSL_USE_GOOGLETEST_HEAD AND ABSL_GOOGLETEST_DOWNLOAD_URL)
      message(FATAL_ERROR "Do not set both ABSL_USE_GOOGLETEST_HEAD and ABSL_GOOGLETEST_DOWNLOAD_URL")
    endif()
    if(ABSL_USE_GOOGLETEST_HEAD)
      set(absl_gtest_download_url "https://github.com/google/googletest/archive/master.zip")
    elseif(ABSL_GOOGLETEST_DOWNLOAD_URL)
      set(absl_gtest_download_url ${ABSL_GOOGLETEST_DOWNLOAD_URL})
    endif()
    if(absl_gtest_download_url)
      set(absl_gtest_src_dir ${CMAKE_BINARY_DIR}/googletest-src)
    else()
      set(absl_gtest_src_dir ${ABSL_LOCAL_GOOGLETEST_DIR})
    endif()
    include(CMake/Googletest/DownloadGTest.cmake)
  endif()

  check_target(gtest)
  check_target(gtest_main)
  check_target(gmock)

  list(APPEND ABSL_TEST_COMMON_LIBRARIES
    gtest_main
    gtest
    gmock
    ${CMAKE_THREAD_LIBS_INIT}
  )
endif()

add_subdirectory(absl)

if(ABSL_ENABLE_INSTALL)
  # absl:lts-remove-begin(system installation is supported for LTS releases)
  # We don't support system-wide installation
  list(APPEND SYSTEM_INSTALL_DIRS "/usr/local" "/usr" "/opt/" "/opt/local" "c:/Program Files/${PROJECT_NAME}")
  if(NOT DEFINED CMAKE_INSTALL_PREFIX OR CMAKE_INSTALL_PREFIX IN_LIST SYSTEM_INSTALL_DIRS)
    message(WARNING "\
  The default and system-level install directories are unsupported except in LTS \
  releases of Abseil.  Please set CMAKE_INSTALL_PREFIX to install Abseil in your \
  source or build tree directly.\
    ")
  endif()
  # absl:lts-remove-end

  # install as a subdirectory only
  install(EXPORT ${PROJECT_NAME}Targets
    NAMESPACE absl::
    DESTINATION "${ABSL_INSTALL_CONFIGDIR}"
  )

  configure_package_config_file(
    CMake/abslConfig.cmake.in
    "${PROJECT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
    INSTALL_DESTINATION "${ABSL_INSTALL_CONFIGDIR}"
  )
  install(FILES "${PROJECT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
    DESTINATION "${ABSL_INSTALL_CONFIGDIR}"
  )

  # Abseil only has a version in LTS releases.  This mechanism is accomplished
  # Abseil's internal Copybara (https://github.com/google/copybara) workflows and
  # isn't visible in the CMake buildsystem itself.
  if(absl_VERSION)
    write_basic_package_version_file(
      "${PROJECT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
      COMPATIBILITY ExactVersion
    )

    install(FILES "${PROJECT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
      DESTINATION ${ABSL_INSTALL_CONFIGDIR}
    )
  endif()  # absl_VERSION

  install(DIRECTORY absl
    DESTINATION ${ABSL_INSTALL_INCLUDEDIR}
    FILES_MATCHING
      PATTERN "*.inc"
      PATTERN "*.h"
      PATTERN "copts" EXCLUDE
      PATTERN "testdata" EXCLUDE
    )
endif()  # ABSL_ENABLE_INSTALL