c++/cmake/CapnProtoTargets.cmake - toolchain/capnproto - Git at Google

 # This CMake script adds imported targets for each shared library and executable distributed by
 # Cap'n Proto's autotools build.
 #
 # This file IS NOT USED by the CMake build! The CMake build generates its own version of this script
 # from its set of exported targets. I used such a generated script as a reference when writing this
 # one.
 #
 # The set of library targets provided by this script is automatically generated from the list of .pc
 # files maintained in configure.ac. The set of executable targets is hard-coded in this file.
 #
 # You can request that this script print debugging information by invoking cmake with:
 #
 #   -DCapnProto_DEBUG=ON
 #
 # TODO(someday): Distinguish between debug and release builds. I.e., set IMPORTED_LOCATION_RELEASE
 #   rather than IMPORTED_LOCATION, etc., if this installation was configured as a release build. But
 #   how do we tell? grep for -g in CXXFLAGS?

 if(CMAKE_VERSION VERSION_LESS 3.1)
   message(FATAL_ERROR "CMake >= 3.1 required")
 endif()

 set(forwarded_config_flags)
 if(CapnProto_FIND_QUIETLY)
   list(APPEND forwarded_config_flags QUIET)
 endif()
 if(CapnProto_FIND_REQUIRED)
   list(APPEND forwarded_config_flags REQUIRED)
 endif()
 # If the consuming project called find_package(CapnProto) with the QUIET or REQUIRED flags, forward
 # them to calls to find_package(PkgConfig) and pkg_check_modules(). Note that find_dependency()
 # would do this for us in the former case, but there is no such forwarding wrapper for
 # pkg_check_modules().

 find_package(PkgConfig ${forwarded_config_flags})
 if(NOT ${PkgConfig_FOUND})
   # If we're here, the REQUIRED flag must not have been passed, else we would have had a fatal
   # error. Nevertheless, a diagnostic for this case is probably nice.
   if(NOT CapnProto_FIND_QUIETLY)
     message(WARNING "pkg-config cannot be found")
   endif()
   set(CapnProto_FOUND OFF)
   return()
 endif()

 function(_capnp_import_pkg_config_target target)
   # Add an imported library target named CapnProto::${target}, using the output of various
   # invocations of `pkg-config ${target}`. The generated imported library target tries to mimic the
   # behavior of a real CMake-generated imported target as closely as possible.
   #
   # Usage: _capnp_import_pkg_config_target(target <all Cap'n Proto targets>)

   set(all_targets ${ARGN})

   pkg_check_modules(${target} ${forwarded_config_flags} ${target})

   if(NOT ${${target}_FOUND})
     if(NOT CapnProto_FIND_QUIETLY)
       message(WARNING "CapnProtoConfig.cmake was configured to search for ${target}.pc, but pkg-config cannot find it. Ignoring this target.")
     endif()
     return()
   endif()

   if(CapnProto_DEBUG)
     # Dump the information pkg-config discovered.
     foreach(var VERSION LIBRARY_DIRS LIBRARIES LDFLAGS_OTHER INCLUDE_DIRS CFLAGS_OTHER)
       message(STATUS "${target}_${var} = ${${target}_${var}}")
     endforeach()
   endif()

   if(NOT ${${target}_VERSION} VERSION_EQUAL ${CapnProto_VERSION})
     if(NOT CapnProto_FIND_QUIETLY)
       message(WARNING "CapnProtoConfig.cmake was configured to search for version ${CapnProto_VERSION}, but ${target} version ${${target}_VERSION} was found. Ignoring this target.")
     endif()
     return()
   endif()

   # Make an educated guess as to what the target's .so and .a filenames must be.
   set(target_name_shared
       ${CMAKE_SHARED_LIBRARY_PREFIX}${target}-${CapnProto_VERSION}${CMAKE_SHARED_LIBRARY_SUFFIX})
   set(target_name_static
       ${CMAKE_STATIC_LIBRARY_PREFIX}${target}${CMAKE_STATIC_LIBRARY_SUFFIX})

   # Find the actual target's file. find_library() sets a cache variable, so I made the variable name
   # unique-ish.
   find_library(CapnProto_${target}_IMPORTED_LOCATION
     NAMES ${target_name_shared} ${target_name_static}  # prefer libfoo-version.so over libfoo.a
     PATHS ${${target}_LIBRARY_DIRS}
     NO_DEFAULT_PATH
   )
   # If the installed version of Cap'n Proto is in a system location, pkg-config will not have filled
   # in ${target}_LIBRARY_DIRS. To account for this, fall back to a regular search.
   find_library(CapnProto_${target}_IMPORTED_LOCATION
     NAMES ${target_name_shared} ${target_name_static}  # prefer libfoo-version.so over libfoo.a
   )

   if(NOT CapnProto_${target}_IMPORTED_LOCATION)
     # Not an error if the library doesn't exist -- we may have found a lite mode installation.
     if(CapnProto_DEBUG)
       message(STATUS "${target} library does not exist")
     endif()
     return()
   endif()

   # Record some information about this target -- shared versus static, location and soname -- which
   # we'll use to build our imported target later.

   set(target_location ${CapnProto_${target}_IMPORTED_LOCATION})
   get_filename_component(target_name "${target_location}" NAME)

   set(target_type STATIC)
   set(imported_soname_property)
   if(target_name STREQUAL ${target_name_shared})
     set(target_type SHARED)
     set(imported_soname_property IMPORTED_SONAME ${target_name})
   endif()

   # Each library dependency of the target is either the target itself, a sibling Cap'n Proto
   # library, or a system library. We ignore the first case by removing this target from the
   # dependencies. The remaining dependencies are either passed through or, if they are a sibling
   # Cap'n Proto library, prefixed with `CapnProto::`.
   set(dependencies ${${target}_LIBRARIES})
   list(REMOVE_ITEM dependencies ${target})
   set(target_interface_libs)
   foreach(dependency ${dependencies})
     list(FIND all_targets ${dependency} target_index)
     # TODO(cleanup): CMake >= 3.3 lets us write: `if(NOT ${dependency} IN_LIST all_targets)`
     if(target_index EQUAL -1)
       list(APPEND target_interface_libs ${dependency})
     else()
       list(APPEND target_interface_libs CapnProto::${dependency})
     endif()
   endforeach()

   add_library(CapnProto::${target} ${target_type} IMPORTED)
   set_target_properties(CapnProto::${target} PROPERTIES
     ${imported_soname_property}
     IMPORTED_LOCATION "${target_location}"
     # TODO(cleanup): Use cxx_std_14 once it's safe to require cmake 3.8.
     INTERFACE_COMPILE_FEATURES "cxx_generic_lambdas"
     INTERFACE_COMPILE_OPTIONS "${${target}_CFLAGS_OTHER}"
     INTERFACE_INCLUDE_DIRECTORIES "${${target}_INCLUDE_DIRS}"

     # I'm dumping LDFLAGS_OTHER in with the libraries because there exists no
     # INTERFACE_LINK_OPTIONS. See https://gitlab.kitware.com/cmake/cmake/issues/16543.
     INTERFACE_LINK_LIBRARIES "${target_interface_libs};${${target}_LDFLAGS_OTHER}"
   )

   if(CapnProto_DEBUG)
     # Dump all the properties we generated for the imported target.
     foreach(prop
         IMPORTED_LOCATION
         IMPORTED_SONAME
         INTERFACE_COMPILE_FEATURES
         INTERFACE_COMPILE_OPTIONS
         INTERFACE_INCLUDE_DIRECTORIES
         INTERFACE_LINK_LIBRARIES)
       get_target_property(value CapnProto::${target} ${prop})
       message(STATUS "CapnProto::${target} ${prop} = ${value}")
     endforeach()
   endif()
 endfunction()

 # ========================================================================================
 # Imported library targets

 # Build a list of targets to search for from the list of .pc files.
 # I.e. [somewhere/foo.pc, somewhere/bar.pc] -> [foo, bar]
 set(library_targets)
 foreach(filename ${CAPNP_PKG_CONFIG_FILES})
   get_filename_component(target ${filename} NAME_WE)
   list(APPEND library_targets ${target})
 endforeach()

 # Try to add an imported library target CapnProto::foo for each foo.pc distributed with Cap'n Proto.
 foreach(target ${library_targets})
   _capnp_import_pkg_config_target(${target} ${library_targets})
 endforeach()

 # Handle lite-mode and no libraries found cases. It is tempting to set a CapnProto_LITE variable
 # here, but the real CMake-generated implementation does no such thing -- we'd need to set it in
 # CapnProtoConfig.cmake.in itself.
 if(TARGET CapnProto::capnp AND TARGET CapnProto::kj)
   if(NOT TARGET CapnProto::capnp-rpc)
     if(NOT CapnProto_FIND_QUIETLY)
       message(STATUS "Found an installation of Cap'n Proto lite. Executable and library targets beyond libkj and libcapnp will be unavailable.")
     endif()
     # Lite mode doesn't include the executables, so return here.
     return()
   endif()
 else()
   # If we didn't even find capnp or kj, then we didn't find anything usable.
   set(CapnProto_FOUND OFF)
   return()
 endif()

 # ========================================================================================
 # Imported executable targets

 get_filename_component(_IMPORT_PREFIX "${CMAKE_CURRENT_LIST_FILE}" PATH)
 get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
 get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
 get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)

 # Add executable targets for the capnp compiler and plugins. This list must be kept manually in sync
 # with the rest of the project.

 add_executable(CapnProto::capnp_tool IMPORTED)
 set_target_properties(CapnProto::capnp_tool PROPERTIES
   IMPORTED_LOCATION "${_IMPORT_PREFIX}/bin/capnp${CMAKE_EXECUTABLE_SUFFIX}"
 )

 add_executable(CapnProto::capnpc_cpp IMPORTED)
 set_target_properties(CapnProto::capnpc_cpp PROPERTIES
   IMPORTED_LOCATION "${_IMPORT_PREFIX}/bin/capnpc-c++${CMAKE_EXECUTABLE_SUFFIX}"
 )

 add_executable(CapnProto::capnpc_capnp IMPORTED)
 set_target_properties(CapnProto::capnpc_capnp PROPERTIES
   IMPORTED_LOCATION "${_IMPORT_PREFIX}/bin/capnpc-capnp${CMAKE_EXECUTABLE_SUFFIX}"
 )
	# This CMake script adds imported targets for each shared library and executable distributed by
	# Cap'n Proto's autotools build.
	#
	# This file IS NOT USED by the CMake build! The CMake build generates its own version of this script
	# from its set of exported targets. I used such a generated script as a reference when writing this
	# one.
	#
	# The set of library targets provided by this script is automatically generated from the list of .pc
	# files maintained in configure.ac. The set of executable targets is hard-coded in this file.
	#
	# You can request that this script print debugging information by invoking cmake with:
	#
	# -DCapnProto_DEBUG=ON
	#
	# TODO(someday): Distinguish between debug and release builds. I.e., set IMPORTED_LOCATION_RELEASE
	# rather than IMPORTED_LOCATION, etc., if this installation was configured as a release build. But
	# how do we tell? grep for -g in CXXFLAGS?

	if(CMAKE_VERSION VERSION_LESS 3.1)
	message(FATAL_ERROR "CMake >= 3.1 required")
	endif()

	set(forwarded_config_flags)
	if(CapnProto_FIND_QUIETLY)
	list(APPEND forwarded_config_flags QUIET)
	endif()
	if(CapnProto_FIND_REQUIRED)
	list(APPEND forwarded_config_flags REQUIRED)
	endif()
	# If the consuming project called find_package(CapnProto) with the QUIET or REQUIRED flags, forward
	# them to calls to find_package(PkgConfig) and pkg_check_modules(). Note that find_dependency()
	# would do this for us in the former case, but there is no such forwarding wrapper for
	# pkg_check_modules().

	find_package(PkgConfig ${forwarded_config_flags})
	if(NOT ${PkgConfig_FOUND})
	# If we're here, the REQUIRED flag must not have been passed, else we would have had a fatal
	# error. Nevertheless, a diagnostic for this case is probably nice.
	if(NOT CapnProto_FIND_QUIETLY)
	message(WARNING "pkg-config cannot be found")
	endif()
	set(CapnProto_FOUND OFF)
	return()
	endif()

	function(_capnp_import_pkg_config_target target)
	# Add an imported library target named CapnProto::${target}, using the output of various
	# invocations of `pkg-config ${target}`. The generated imported library target tries to mimic the
	# behavior of a real CMake-generated imported target as closely as possible.
	#
	# Usage: _capnp_import_pkg_config_target(target <all Cap'n Proto targets>)

	set(all_targets ${ARGN})

	pkg_check_modules(${target} ${forwarded_config_flags} ${target})

	if(NOT ${${target}_FOUND})
	if(NOT CapnProto_FIND_QUIETLY)
	message(WARNING "CapnProtoConfig.cmake was configured to search for ${target}.pc, but pkg-config cannot find it. Ignoring this target.")
	endif()
	return()
	endif()

	if(CapnProto_DEBUG)
	# Dump the information pkg-config discovered.
	foreach(var VERSION LIBRARY_DIRS LIBRARIES LDFLAGS_OTHER INCLUDE_DIRS CFLAGS_OTHER)
	message(STATUS "${target}_${var} = ${${target}_${var}}")
	endforeach()
	endif()

	if(NOT ${${target}_VERSION} VERSION_EQUAL ${CapnProto_VERSION})
	if(NOT CapnProto_FIND_QUIETLY)
	message(WARNING "CapnProtoConfig.cmake was configured to search for version ${CapnProto_VERSION}, but ${target} version ${${target}_VERSION} was found. Ignoring this target.")
	endif()
	return()
	endif()

	# Make an educated guess as to what the target's .so and .a filenames must be.
	set(target_name_shared
	${CMAKE_SHARED_LIBRARY_PREFIX}${target}-${CapnProto_VERSION}${CMAKE_SHARED_LIBRARY_SUFFIX})
	set(target_name_static
	${CMAKE_STATIC_LIBRARY_PREFIX}${target}${CMAKE_STATIC_LIBRARY_SUFFIX})

	# Find the actual target's file. find_library() sets a cache variable, so I made the variable name
	# unique-ish.
	find_library(CapnProto_${target}_IMPORTED_LOCATION
	NAMES ${target_name_shared} ${target_name_static} # prefer libfoo-version.so over libfoo.a
	PATHS ${${target}_LIBRARY_DIRS}
	NO_DEFAULT_PATH
	)
	# If the installed version of Cap'n Proto is in a system location, pkg-config will not have filled
	# in ${target}_LIBRARY_DIRS. To account for this, fall back to a regular search.
	find_library(CapnProto_${target}_IMPORTED_LOCATION
	NAMES ${target_name_shared} ${target_name_static} # prefer libfoo-version.so over libfoo.a
	)

	if(NOT CapnProto_${target}_IMPORTED_LOCATION)
	# Not an error if the library doesn't exist -- we may have found a lite mode installation.
	if(CapnProto_DEBUG)
	message(STATUS "${target} library does not exist")
	endif()
	return()
	endif()

	# Record some information about this target -- shared versus static, location and soname -- which
	# we'll use to build our imported target later.

	set(target_location ${CapnProto_${target}_IMPORTED_LOCATION})
	get_filename_component(target_name "${target_location}" NAME)

	set(target_type STATIC)
	set(imported_soname_property)
	if(target_name STREQUAL ${target_name_shared})
	set(target_type SHARED)
	set(imported_soname_property IMPORTED_SONAME ${target_name})
	endif()

	# Each library dependency of the target is either the target itself, a sibling Cap'n Proto
	# library, or a system library. We ignore the first case by removing this target from the
	# dependencies. The remaining dependencies are either passed through or, if they are a sibling
	# Cap'n Proto library, prefixed with `CapnProto::`.
	set(dependencies ${${target}_LIBRARIES})
	list(REMOVE_ITEM dependencies ${target})
	set(target_interface_libs)
	foreach(dependency ${dependencies})
	list(FIND all_targets ${dependency} target_index)
	# TODO(cleanup): CMake >= 3.3 lets us write: `if(NOT ${dependency} IN_LIST all_targets)`
	if(target_index EQUAL -1)
	list(APPEND target_interface_libs ${dependency})
	else()
	list(APPEND target_interface_libs CapnProto::${dependency})
	endif()
	endforeach()

	add_library(CapnProto::${target} ${target_type} IMPORTED)
	set_target_properties(CapnProto::${target} PROPERTIES
	${imported_soname_property}
	IMPORTED_LOCATION "${target_location}"
	# TODO(cleanup): Use cxx_std_14 once it's safe to require cmake 3.8.
	INTERFACE_COMPILE_FEATURES "cxx_generic_lambdas"
	INTERFACE_COMPILE_OPTIONS "${${target}_CFLAGS_OTHER}"
	INTERFACE_INCLUDE_DIRECTORIES "${${target}_INCLUDE_DIRS}"

	# I'm dumping LDFLAGS_OTHER in with the libraries because there exists no
	# INTERFACE_LINK_OPTIONS. See https://gitlab.kitware.com/cmake/cmake/issues/16543.
	INTERFACE_LINK_LIBRARIES "${target_interface_libs};${${target}_LDFLAGS_OTHER}"
	)

	if(CapnProto_DEBUG)
	# Dump all the properties we generated for the imported target.
	foreach(prop
	IMPORTED_LOCATION
	IMPORTED_SONAME
	INTERFACE_COMPILE_FEATURES
	INTERFACE_COMPILE_OPTIONS
	INTERFACE_INCLUDE_DIRECTORIES
	INTERFACE_LINK_LIBRARIES)
	get_target_property(value CapnProto::${target} ${prop})
	message(STATUS "CapnProto::${target} ${prop} = ${value}")
	endforeach()
	endif()
	endfunction()

	# ========================================================================================
	# Imported library targets

	# Build a list of targets to search for from the list of .pc files.
	# I.e. [somewhere/foo.pc, somewhere/bar.pc] -> [foo, bar]
	set(library_targets)
	foreach(filename ${CAPNP_PKG_CONFIG_FILES})
	get_filename_component(target ${filename} NAME_WE)
	list(APPEND library_targets ${target})
	endforeach()

	# Try to add an imported library target CapnProto::foo for each foo.pc distributed with Cap'n Proto.
	foreach(target ${library_targets})
	_capnp_import_pkg_config_target(${target} ${library_targets})
	endforeach()

	# Handle lite-mode and no libraries found cases. It is tempting to set a CapnProto_LITE variable
	# here, but the real CMake-generated implementation does no such thing -- we'd need to set it in
	# CapnProtoConfig.cmake.in itself.
	if(TARGET CapnProto::capnp AND TARGET CapnProto::kj)
	if(NOT TARGET CapnProto::capnp-rpc)
	if(NOT CapnProto_FIND_QUIETLY)
	message(STATUS "Found an installation of Cap'n Proto lite. Executable and library targets beyond libkj and libcapnp will be unavailable.")
	endif()
	# Lite mode doesn't include the executables, so return here.
	return()
	endif()
	else()
	# If we didn't even find capnp or kj, then we didn't find anything usable.
	set(CapnProto_FOUND OFF)
	return()
	endif()

	# ========================================================================================
	# Imported executable targets

	get_filename_component(_IMPORT_PREFIX "${CMAKE_CURRENT_LIST_FILE}" PATH)
	get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
	get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
	get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)

	# Add executable targets for the capnp compiler and plugins. This list must be kept manually in sync
	# with the rest of the project.

	add_executable(CapnProto::capnp_tool IMPORTED)
	set_target_properties(CapnProto::capnp_tool PROPERTIES
	IMPORTED_LOCATION "${_IMPORT_PREFIX}/bin/capnp${CMAKE_EXECUTABLE_SUFFIX}"
	)

	add_executable(CapnProto::capnpc_cpp IMPORTED)
	set_target_properties(CapnProto::capnpc_cpp PROPERTIES
	IMPORTED_LOCATION "${_IMPORT_PREFIX}/bin/capnpc-c++${CMAKE_EXECUTABLE_SUFFIX}"
	)

	add_executable(CapnProto::capnpc_capnp IMPORTED)
	set_target_properties(CapnProto::capnpc_capnp PROPERTIES
	IMPORTED_LOCATION "${_IMPORT_PREFIX}/bin/capnpc-capnp${CMAKE_EXECUTABLE_SUFFIX}"
	)