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[WIP] CMake Install rule proposal #182

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[WIP] CMake Install rule proposal #182

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41 changes: 31 additions & 10 deletions CMake/AbseilHelpers.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -58,11 +58,11 @@ set(ABSL_IDE_FOLDER Abseil)
# SRCS
# "b.cc"
# DEPS
# absl_internal_awesome # not "awesome"!
# absl::awesome
# )
#
# If PUBLIC is set, absl_cc_library will instead create a target named
# absl_${NAME} and still an alias absl::${NAME}.
# Warning: Only libraries with the PUBLIC flag set can be used by user.
# Otherwise they are internal absl targets that shouldn't be used externally.
#
# absl_cc_library(
# NAME
Expand All @@ -76,14 +76,18 @@ set(ABSL_IDE_FOLDER Abseil)
# TODO: Implement "ALWAYSLINK"
function(absl_cc_library)
cmake_parse_arguments(ABSL_CC_LIB
"DISABLE_INSTALL;PUBLIC;TESTONLY"
"PUBLIC;TESTONLY"
"NAME"
"HDRS;SRCS;COPTS;DEFINES;LINKOPTS;DEPS"
${ARGN}
)

if (NOT ABSL_CC_LIB_TESTONLY OR ABSL_RUN_TESTS)
set(_NAME "absl_${ABSL_CC_LIB_NAME}")
if(NOT ABSL_ENABLE_INSTALL)
set(_NAME "absl_${ABSL_CC_LIB_NAME}")
else()
set(_NAME "${ABSL_CC_LIB_NAME}")
endif()

# Check if this is a header-only library
# Note that as of February 2019, many popular OS's (for example, Ubuntu
Expand All @@ -103,9 +107,14 @@ function(absl_cc_library)

if(NOT ABSL_CC_LIB_IS_INTERFACE)
add_library(${_NAME} STATIC "")
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@dennisklein dennisklein Jan 8, 2019 •
edited
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To support shared libraries (Please ignore, if this is not a desired feature at all):

Suggested change
add_library(${_NAME} STATIC "")
add_library(${_NAME})

The user can now choose between static and shared libraries via -DBUILD_SHARED_LIBS=ON/OFF. For good practice, you may want to explicitely declare this build switch with an explicit default via option(). Without declaring it as an option, the default is OFF (=> static).

Because there are library dependencies within the absl package, it is recommended to add relative RPATH entries for relocatability. Here is a snippet how we usually add such entries on Linux and MacOS:

set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
list(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}" isSystemDir)
if("${isSystemDir}" STREQUAL "-1")
  if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
    set(CMAKE_EXE_LINKER_FLAGS ${CMAKE_EXE_LINKER_FLAGS} "-Wl,--enable-new-dtags")
    set(CMAKE_SHARED_LINKER_FLAGS ${CMAKE_SHARED_LINKER_FLAGS} "-Wl,--enable-new-dtags")
    set(CMAKE_INSTALL_RPATH "$ORIGIN/../${CMAKE_INSTALL_LIBDIR}")
  elseif(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
    set(CMAKE_INSTALL_RPATH "@loader_path/../${CMAKE_INSTALL_LIBDIR}")
  endif()
endif()

set_target_properties(${_NAME} PROPERTIES
OUTPUT_NAME "absl_${_NAME}"
)
target_sources(${_NAME} PRIVATE ${ABSL_CC_LIB_SRCS} ${ABSL_CC_LIB_HDRS})
target_include_directories(${_NAME}
PUBLIC ${ABSL_COMMON_INCLUDE_DIRS})
target_include_directories(${_NAME} PUBLIC
$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>
$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}> # <prefix>/include
)
target_compile_options(${_NAME}
PRIVATE ${ABSL_CC_LIB_COPTS})
target_link_libraries(${_NAME}
Expand All @@ -129,15 +138,27 @@ function(absl_cc_library)
else()
# Generating header-only library
add_library(${_NAME} INTERFACE)
target_include_directories(${_NAME}
INTERFACE ${ABSL_COMMON_INCLUDE_DIRS})
target_include_directories(${_NAME} INTERFACE
$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>
$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}> # <prefix>/include
)
target_link_libraries(${_NAME}
INTERFACE ${ABSL_CC_LIB_DEPS} ${ABSL_CC_LIB_LINKOPTS}
)
target_compile_definitions(${_NAME} INTERFACE ${ABSL_CC_LIB_DEFINES})
endif()

add_library(absl::${ABSL_CC_LIB_NAME} ALIAS ${_NAME})

# install rules
if(ABSL_ENABLE_INSTALL)
install(TARGETS ${_NAME}
EXPORT ${PROJECT_NAME}Targets
ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)
endif()
endif()
endfunction()

Expand Down Expand Up @@ -194,7 +215,7 @@ function(absl_cc_test)
add_executable(${_NAME} "")
target_sources(${_NAME} PRIVATE ${ABSL_CC_TEST_SRCS})
target_include_directories(${_NAME}
PUBLIC ${ABSL_COMMON_INCLUDE_DIRS}
PUBLIC $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>
PRIVATE ${GMOCK_INCLUDE_DIRS} ${GTEST_INCLUDE_DIRS}
)
target_compile_definitions(${_NAME}
Expand Down
7 changes: 7 additions & 0 deletions CMake/abslConfig.cmake.in
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
## absl CMake configuration file

set(ABSL_VERSION @PROJECT_VERSION@)

@PACKAGE_INIT@

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@dennisklein dennisklein Jan 8, 2019 •
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It would be nice to have more meta data here, e.g.

set_and_check(@PROJECT_NAME@_HOME "${PACKAGE_PREFIX_DIR}")
set_and_check(@PROJECT_NAME@_INCLUDEDIR "${PACKAGE_PREFIX_DIR}/@CMAKE_INSTALL_INCLUDEDIR@")
set_and_check(@PROJECT_NAME@_LIBDIR "${PACKAGE_PREFIX_DIR}/@CMAKE_INSTALL_LIBDIR@")

set(@PROJECT_NAME@_TARGETS absl::* absl::*_internal)
set(@PROJECT_NAME@_PUBLIC_TARGETS absl::*)
set(@PROJECT_NAME@_PRIVATE_TARGETS absl::*_internal)

The paths may be extracted from the target properties, but experience shows, it is nicer to have them at hand in a convenient variable (${PACKAGE_PREFIX_DIR} is populated by the code generated via @PACKAGE_INIT@ at import time).

The entries in the proposed target lists could e.g. easily be collected in the absl_cc_library function.

Note: @PROJECT_NAME@ is case-sensitive. You may wish to convert to upper case characters.

Note: If you decide to export a path via set_and_check as proposed in my example above, make sure, this is done only in the cases, when something is installed into these paths. E.g. if you had a build option, which would result in nothing being installed into the lib directory, it is likely the lib directory will not be created and set_and_check will fail.

include ("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")
61 changes: 55 additions & 6 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -22,21 +22,31 @@
cmake_minimum_required(VERSION 3.5)

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

project(absl)
# Enable MACOSX_RPATH by default.
if(POLICY CMP0042)
cmake_policy (SET CMP0042 NEW)
endif()

project(absl VERSION 1.0.0 LANGUAGES CXX)

option(ABSL_ENABLE_INSTALL "If ON, Abseil enable install rules." ON)
# 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 "^${PROJECT_SOURCE_DIR}$")
set(ABSL_ENABLE_INSTALL OFF)
endif()

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

include(GNUInstallDirs)
include(AbseilHelpers)


##
## Using absl targets
##
Expand All @@ -47,7 +57,6 @@ include(AbseilHelpers)
##
## DO NOT rely on the internal targets outside of the prefix


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

Expand Down Expand Up @@ -75,7 +84,6 @@ endif()

## check targets
if(BUILD_TESTING)

if(${ABSL_USE_GOOGLETEST_HEAD})
include(CMake/DownloadGTest.cmake)
endif()
Expand All @@ -93,3 +101,44 @@ if(BUILD_TESTING)
endif()

add_subdirectory(absl)

# install rules
if(ABSL_ENABLE_INSTALL)
# See https://cmake.org/cmake/help/latest/module/GNUInstallDirs.html
include(GNUInstallDirs)
# See https://cmake.org/cmake/help/latest/command/find_package.html#search-procedure
set(CMAKE_INSTALL_CONFIGDIR ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
install(
EXPORT ${PROJECT_NAME}Targets
NAMESPACE absl::
DESTINATION ${CMAKE_INSTALL_CONFIGDIR}
)
install(
DIRECTORY absl
DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
COMPONENT Devel
FILES_MATCHING
PATTERN "*.inc"
PATTERN "*.h"
)

# See https://cmake.org/cmake/help/latest/module/CMakePackageConfigHelpers.html
include(CMakePackageConfigHelpers)
configure_package_config_file(
CMake/abslConfig.cmake.in
"${PROJECT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
INSTALL_DESTINATION "${CMAKE_INSTALL_CONFIGDIR}"
NO_CHECK_REQUIRED_COMPONENTS_MACRO
)
write_basic_package_version_file(
"${PROJECT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
COMPATIBILITY ExactVersion
)
install(
FILES
"${PROJECT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
"${PROJECT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
DESTINATION "${CMAKE_INSTALL_CONFIGDIR}"
COMPONENT Devel
)
endif()