207 lines
8.3 KiB
CMake
207 lines
8.3 KiB
CMake
# ~~~
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# Copyright 2019 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ~~~
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#[=======================================================================[.rst:
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FindProtobufTargets
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-------------------
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A module to use `Protobuf` with less complications.
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Using ``find_package(Protobuf)`` should be simple, but it is not.
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CMake provides a ``FindProtobuf`` module. Unfortunately it does not generate
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`protobuf::*` targets until CMake-3.9, and `protobuf::protoc` does not
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appear until CMake-3.10.
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The CMake-config files generated by `protobuf` always create these targets,
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but on some Linux distributions (e.g. Fedora>=29, and openSUSE-Tumbleweed) there
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are system packages for protobuf, but these packages are installed without the
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CMake-config files. One must either use the ``FindProtobuf`` module, find the
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libraries via `pkg-config`, or find the libraries manually.
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When the CMake-config files are installed they produce the same targets as
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recent versions of ``FindProtobuf``. However, they do not produce the
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`Protobuf_LIBRARY`, `Protobuf_INCLUDE_DIR`, etc. that are generated by the
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module. Furthermore, the `protobuf::protoc` library is not usable when loaded
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from the CMake-config files: its ``IMPORTED_LOCATION`` variable is not defined.
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This module is designed to provide a single, uniform, ``find_package()``
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module that always produces the same outputs:
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- It always generates the ``protobuf::*`` targets.
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- It always defines ``ProtobufTargets_FOUND`` and ``ProtobufTargets_VERSION``.
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- It *prefers* using the CMake config files if they are available.
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- It fallsback on the ``FindProtobuf`` module if the config files are not found.
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- It populates any missing targets and their properties.
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The following :prop_tgt:`IMPORTED` targets are defined:
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``protobuf::libprotobuf``
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The protobuf library.
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``protobuf::libprotobuf-lite``
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The protobuf lite library.
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``protobuf::libprotoc``
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The protoc library.
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``protobuf::protoc``
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The protoc compiler.
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Example:
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.. code-block:: cmake
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find_package(ProtobufTargets REQUIRED)
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add_executable(bar bar.cc)
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target_link_libraries(bar PRIVATE protobuf::libprotobuf)
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#]=======================================================================]
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if (protobuf_DEBUG)
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message(STATUS "[ ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE} ] "
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"protobuf_USE_STATIC_LIBS = ${protobuf_USE_STATIC_LIBS}"
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" ProtobufTargets = ${ProtobufTargets_FOUND}")
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endif ()
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# Always load thread support, even on Windows.
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find_package(Threads REQUIRED)
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# First try to use the ``protobufConfig.cmake`` or ``protobuf-config.cmake``
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# file if it was installed. This is common on systems (or package managers)
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# where protobuf was compiled and installed with `CMake`. Note that on Linux
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# this *must* be all lowercase ``protobuf``, while on Windows it does not
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# matter.
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find_package(protobuf CONFIG)
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if (protobuf_DEBUG)
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message(STATUS "[ ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE} ] "
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"protobuf_FOUND = ${protobuf_FOUND}"
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" protobuf_VERSION = ${protobuf_VERSION}")
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endif ()
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if (protobuf_FOUND)
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set(ProtobufTargets_FOUND 1)
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set(ProtobufTargets_VERSION ${protobuf_VERSION})
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if (protobuf_DEBUG)
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message(
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STATUS "[ ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE} ] "
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"ProtobufTargets_FOUND = ${ProtobufTargets_FOUND}"
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" ProtobufTargets_VERSION = ${ProtobufTargets_VERSION}")
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endif ()
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else()
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find_package(Protobuf QUIET)
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if (Protobuf_FOUND)
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set(ProtobufTargets_FOUND 1)
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set(ProtobufTargets_VERSION ${Protobuf_VERSION})
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if (NOT TARGET protobuf::libprotobuf)
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add_library(protobuf::libprotobuf INTERFACE IMPORTED)
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set_property(TARGET protobuf::libprotobuf
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PROPERTY INTERFACE_INCLUDE_DIRECTORIES
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${Protobuf_INCLUDE_DIR})
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set_property(TARGET protobuf::libprotobuf
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APPEND
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PROPERTY INTERFACE_LINK_LIBRARIES ${Protobuf_LIBRARY}
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Threads::Threads)
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endif ()
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if (NOT TARGET protobuf::libprotobuf-lite)
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add_library(protobuf::libprotobuf-lite INTERFACE IMPORTED)
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set_property(TARGET protobuf::libprotobuf-lite
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PROPERTY INTERFACE_INCLUDE_DIRECTORIES
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${Protobuf_INCLUDE_DIR})
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set_property(TARGET protobuf::libprotobuf-lite
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APPEND
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PROPERTY INTERFACE_LINK_LIBRARIES
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${Protobuf_LITE_LIBRARY} Threads::Threads)
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endif ()
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if (NOT TARGET protobuf::libprotoc)
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add_library(protobuf::libprotoc INTERFACE IMPORTED)
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set_property(TARGET protobuf::libprotoc
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PROPERTY INTERFACE_INCLUDE_DIRECTORIES
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${Protobuf_INCLUDE_DIR})
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set_property(TARGET protobuf::libprotoc
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APPEND
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PROPERTY INTERFACE_LINK_LIBRARIES
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${Protobuf_PROTOC_LIBRARY} Threads::Threads)
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endif ()
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endif ()
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endif ()
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if (protobuf_DEBUG)
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message(STATUS "[ ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE} ] "
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"ProtobufTargets_FOUND = ${ProtobufTargets_FOUND}"
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" ProtobufTargets_VERSION = ${ProtobufTargets_VERSION}")
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endif ()
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# We also should try to find the protobuf C++ plugin for the protocol buffers
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# compiler.
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if (ProtobufTargets_FOUND AND NOT TARGET protobuf::protoc)
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add_executable(protobuf::protoc IMPORTED)
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# Discover the protoc compiler location.
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find_program(_protobuf_PROTOC_EXECUTABLE
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NAMES protoc
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DOC "The Google Protocol Buffers Compiler")
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if (protobuf_DEBUG)
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message(
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STATUS "[ ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE} ] "
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"ProtobufTargets_FOUND = ${ProtobufTargets_FOUND}"
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" ProtobufTargets_VERSION = ${ProtobufTargets_VERSION}"
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" EXE = ${_protobuf_PROTOC_EXECUTABLE}")
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endif ()
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set_property(TARGET protobuf::protoc
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PROPERTY IMPORTED_LOCATION ${_protobuf_PROTOC_EXECUTABLE})
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set_property(
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TARGET protobuf::protoc
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PROPERTY IMPORTED_LOCATION_DEBUG ${_protobuf_PROTOC_EXECUTABLE})
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set_property(TARGET protobuf::protoc
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PROPERTY IMPORTED_LOCATION_RELEASE
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${_protobuf_PROTOC_EXECUTABLE})
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unset(_protobuf_PROTOC_EXECUTABLE)
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if (protobuf_DEBUG)
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get_target_property(_protobuf_PROTOC_EXECUTABLE protobuf::protoc
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IMPORTED_LOCATION)
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message(
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STATUS "[ ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE} ] "
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"LOCATION=${_protobuf_PROTOC_EXECUTABLE}")
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endif ()
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endif ()
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if (protobuf_DEBUG)
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message(STATUS "[ ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE} ] "
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"ProtobufTargets_FOUND = ${ProtobufTargets_FOUND}"
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" ProtobufTargets_VERSION = ${ProtobufTargets_VERSION}")
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if (ProtobufTargets_FOUND)
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foreach (_target
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protobuf::libprotobuf
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protobuf::libprotobuf-lite
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protobuf::libprotoc)
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if (NOT TARGET ${_target})
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message(
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STATUS
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"[ ${CMAKE_CURRENT_LIST_FILE}:${CMAKE_CURRENT_LIST_LINE} ] "
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"target=${_target} is NOT a target")
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endif ()
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endforeach ()
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unset(_target)
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endif ()
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endif ()
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find_package_handle_standard_args(ProtobufTargets
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REQUIRED_VARS
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ProtobufTargets_FOUND
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ProtobufTargets_VERSION)
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