grpc找不到protobuf库

我检查了 grpc 安装并完成了构建和安装。

现在当我尝试：

find_package(gRPC CONFIG REQUIRED)

I get

CMake Error at CMakeLists.txt:15 (find_package):
  Found package configuration file:

    /usr/lib64/cmake/grpc/gRPCConfig.cmake

  but it set gRPC_FOUND to FALSE so package "gRPC" is considered to be NOT
  FOUND.  Reason given by package:

  The following imported targets are referenced, but are missing:
  protobuf::libprotobuf protobuf::libprotoc

事件虽然

find_package(Protobuf REQUIRED)

效果很好。

我读到我应该跑步cmake ../.. -DBUILD_DEPS=ON -DBUILD_SHARED_LIBS=ON来解决这个问题。然而，这会导致：

CMake Error at cmake/abseil-cpp.cmake:38 (find_package):
  Could not find a package configuration file provided by "absl" with any of
  the following names:

    abslConfig.cmake
    absl-config.cmake

  Add the installation prefix of "absl" to CMAKE_PREFIX_PATH or set
  "absl_DIR" to a directory containing one of the above files.  If "absl"
  provides a separate development package or SDK, be sure it has been
  installed.
Call Stack (most recent call first):
  CMakeLists.txt:191 (include)


-- Configuring incomplete, errors occurred!
See also "/home/ray/CLionProjects/grpc/grpc/CMakeFiles/CMakeOutput.log".
See also "/home/ray/CLionProjects/grpc/grpc/CMakeFiles/CMakeError.log".

/usr/lib64/cmake/grpc/gRPCConfig.cmake的内容

# Module path
list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR}/modules)

# Depend packages






# Targets
include(${CMAKE_CURRENT_LIST_DIR}/gRPCTargets.cmake)

问题实际上出在您使用的项目上find_package()及其包文件（/usr/lib64/cmake/grpc/gRPCConfig.cmake在你的情况下）。错误信息

The following imported targets are referenced, but are missing:

意味着包文件引用了 IMPORTED 目标，但它们从未定义。

该问题的常见原因如下：

1. 在其自己的构建过程中，该项目使用find_package()对于一些其他包。这find_package()call 定义了 IMPORTED 目标，这些目标在项目中用于链接。

2. 它的包文件包含由以下命令创建的脚本install(EXPORT)命令并根据install(TARGETS ... EXPORT ...)命令。此包含的脚本使用 IMPORTED 目标，但未定义它们。

3. 项目的包文件forgets to use find_package， 或更好，查找依赖项 https://cmake.org/cmake/help/v3.9/module/CMakeFindDependencyMacro.html用于为包含的脚本定义 IMPORTED 目标。

如果您不想修复（其他）项目的包文件，那么最直接的解决方案是添加错过的find_package进入你自己的项目：

# Hack: This will define IMPORTED targets, needed for gRPC project, but not defined by it.
find_package(Protobuf REQUIRED)
# Now perform the original 'find_package' call.
find_package(gRPC CONFIG REQUIRED)

实际上，gRPCConfig.cmake包文件旨在包含调用find_package(Protobuf)。它的模板cmake/gRPCConfig.cmake.in https://github.com/grpc/grpc/blob/master/cmake/gRPCConfig.cmake.in如下：

# Module path
list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR}/modules)

# Depend packages
@_gRPC_FIND_ZLIB@
@_gRPC_FIND_PROTOBUF@
@_gRPC_FIND_SSL@
@_gRPC_FIND_CARES@
@_gRPC_FIND_ABSL@

# Targets
include(${CMAKE_CURRENT_LIST_DIR}/gRPCTargets.cmake)

并在替换变量_gRPC_FIND_PROTOBUF应发出以下代码：

if(NOT Protobuf_FOUND AND NOT PROTOBUF_FOUND)
  find_package(Protobuf ${gRPC_PROTOBUF_PACKAGE_TYPE})
endif()

（该变量应设置为cmake/protobuf.cmake https://github.com/grpc/grpc/blob/master/cmake/protobuf.cmake).

但出现了问题，结果是/usr/lib64/cmake/grpc/gRPCConfig.cmake包含空变量的替换：

# Module path
list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR}/modules)

# Depend packages






# Targets
include(${CMAKE_CURRENT_LIST_DIR}/gRPCTargets.cmake)