添加 --coverage 標志時對 grpc::experimental 的 vtable 的未定義引用

Question

我有一個基於 CMake 的 C++ 項目。該項目的起點是使用 cmake-init 創建的。 我正在嘗試將 gRPC 添加到項目中。 但是，當使用覆蓋標志時，會出現 linker 錯誤：

build] /usr/bin/ld: CMakeFiles/demo_lib.dir/source/lib.cpp.o: warning: relocation against `_ZTVN4grpc12experimental38FileWatcherAuthorizationPolicyProviderE' in read-only section `.text._ZN4grpc12experimental38FileWatcherAuthorizationPolicyProviderC2EP34grpc_authorization_policy_provider[_ZN4grpc12experimental38FileWatcherAuthorizationPolicyProviderC5EP34grpc_authorization_policy_provider]'
[build] /usr/bin/ld: /usr/bin/ld: ../CMakeFiles/demo_lib.dir/source/lib.cpp.o: warning: relocation against `_ZTVN4grpc12experimental38FileWatcherAuthorizationPolicyProviderE' in read-only section `.text._ZN4grpc12experimental38FileWatcherAuthorizationPolicyProviderC2EP34grpc_authorization_policy_provider[_ZN4grpc12experimental38FileWatcherAuthorizationPolicyProviderC5EP34grpc_authorization_policy_provider]'
[build] /usr/bin/ld: ../CMakeFiles/demo_lib.dir/source/lib.cpp.o: in function `grpc::experimental::StaticDataAuthorizationPolicyProvider::StaticDataAuthorizationPolicyProvider(grpc_authorization_policy_provider*)':
[build] /home/toto/development/cmake-init-tuto/demo/build/coverage/vcpkg_installed/x64-linux/include/grpcpp/security/authorization_policy_provider.h:48: undefined reference to `vtable for grpc::experimental::StaticDataAuthorizationPolicyProvider'
[build] /usr/bin/ld: ../CMakeFiles/demo_lib.dir/source/lib.cpp.o: in function `grpc::experimental::FileWatcherAuthorizationPolicyProvider::FileWatcherAuthorizationPolicyProvider(grpc_authorization_policy_provider*)':
[build] /home/toto/development/cmake-init-tuto/demo/build/coverage/vcpkg_installed/x64-linux/include/grpcpp/security/authorization_policy_provider.h:73: undefined reference to `vtable for grpc::experimental::FileWatcherAuthorizationPolicyProvider'
[build] CMakeFiles/demo_lib.dir/source/lib.cpp.o: in function `grpc::experimental::StaticDataAuthorizationPolicyProvider::StaticDataAuthorizationPolicyProvider(grpc_authorization_policy_provider*)':
[build] /home/toto/development/cmake-init-tuto/demo/build/coverage/vcpkg_installed/x64-linux/include/grpcpp/security/authorization_policy_provider.h:48: undefined reference to `vtable for grpc::experimental::StaticDataAuthorizationPolicyProvider'
[build] /usr/bin/ld: CMakeFiles/demo_lib.dir/source/lib.cpp.o: in function `grpc::experimental::FileWatcherAuthorizationPolicyProvider::FileWatcherAuthorizationPolicyProvider(grpc_authorization_policy_provider*)':
[build] /home/toto/development/cmake-init-tuto/demo/build/coverage/vcpkg_installed/x64-linux/include/grpcpp/security/authorization_policy_provider.h:73: undefined reference to `vtable for grpc::experimental::FileWatcherAuthorizationPolicyProvider'

與這里的類似問題不同的是，如果沒有覆蓋標志，這不會發生 + 我不以任何方式使用 AuthorizationPolicy。 我現在使用的代碼基本上是您可以在https://github.com/faaxm/exmpl-cmake-grpc中找到的代碼

這是 CMakePresets.json 中的相關標志：

{
      "name": "flags-unix",
      "hidden": true,
      "cacheVariables": {
        "CMAKE_CXX_FLAGS": "-Wall -Wextra -Wpedantic -Wconversion -Wsign-conversion -Wcast-qual -Wformat=2 -Wundef -Werror=float-equal -Wshadow -Wcast-align -Wunused -Wnull-dereference -Wdouble-promotion -Wimplicit-fallthrough -Wextra-semi -Woverloaded-virtual -Wnon-virtual-dtor -Wold-style-cast -Wl,--whole-archive -Wl,--allow-multiple-definition"
      }
    },
{
      "name": "coverage-unix",
      "binaryDir": "${sourceDir}/build/coverage",
      "inherits": "ci-unix",
      "hidden": true,
      "cacheVariables": {
        "ENABLE_COVERAGE": "ON",
        "CMAKE_BUILD_TYPE": "Coverage",
        "CMAKE_CXX_FLAGS_COVERAGE": "-Og -g --coverage -fkeep-inline-functions -fkeep-static-functions",
        "CMAKE_EXE_LINKER_FLAGS_COVERAGE": "--coverage",
        "CMAKE_SHARED_LINKER_FLAGS_COVERAGE": "--coverage",
        "CMAKE_MAP_IMPORTED_CONFIG_COVERAGE": "Coverage;RelWithDebInfo;Release;Debug;"
      }
    },

編輯：

引用的header在這里： https://grpc.github.io/grpc/cpp/authorization__policy__provider_8h_source.html （只有80行）。 在我看來，沒有定義任何純虛擬方法。 我錯了嗎？

這是源文件的樣子： https://github.com/faaxm/exmpl-cmake-grpc/blob/master/server/src/main.cpp除了在我的例子中，它是一個void launch_server() function int main() ，而實際的int main()調用launch_server() 。 我得到的一個（可能）提示是ServerBuilder class ('grpcpp/server_builder.h') 具有：

class ServerBuilder {
 public:
  ServerBuilder();
  virtual ~ServerBuilder();
  // (...)
  /// NOTE: class experimental_type is not part of the public API of this class.
  /// TODO(yashykt): Integrate into public API when this is no longer
  /// experimental.
  class experimental_type {
   public:
    // (...)

    /// Sets server authorization policy provider in
    /// GRPC_ARG_AUTHORIZATION_POLICY_PROVIDER channel argument.
    void SetAuthorizationPolicyProvider(
        std::shared_ptr<experimental::AuthorizationPolicyProviderInterface>
            provider);

   private:
    ServerBuilder* builder_;
  };
  //(...)
  private:
  std::shared_ptr<experimental::AuthorizationPolicyProviderInterface>
      authorization_provider_;

這是 AuthorizationPolicyProvider 通過 gRPC ServerBuilder class 以某種方式進入我的代碼的唯一方法。那我該怎么辦？

Answer 1

IIRC 這與稱為Position Independent Code的東西有關。 您基本上有一個 static 庫，您希望將其鏈接到共享庫中（這很可能是由--coverage標志引起的），如果沒有 position 獨立代碼，您將無法做到這一點。 您需要做的是通過傳遞-fPIC重新編譯 static 庫。

然后你可以重新編譯你的項目，它應該可以工作。

編輯： 這里是一個 stackoverflow 問題的鏈接，其中解釋了如何確定庫是否是使用-fPIC編譯的。