Fix CMake protobuf include order

src/brpc/CMakeLists.txt

@@ -208,7 +208,8 @@ if(WITH_URMA AND URMA_USE_MOCK_ENABLED)
     target_compile_features(brpc_build_config INTERFACE cxx_std_17)
 endif()
 target_include_directories(brpc_build_config BEFORE INTERFACE
-    ${CMAKE_CURRENT_BINARY_DIR})
+    ${CMAKE_CURRENT_BINARY_DIR}
+    ${Protobuf_INCLUDE_DIRS})
 target_compile_definitions(brpc_build_config INTERFACE ${BRPC_DEFINITIONS})
 target_include_directories(brpc_build_config INTERFACE ${BRPC_INCLUDE_DIRS})
 

src/butil/CMakeLists.txt

@@ -46,7 +46,9 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/config.h.in
 get_filename_component(butil_generated_include_dir
     "${CMAKE_CURRENT_BINARY_DIR}/.." ABSOLUTE)
 
-set(BUTIL_INCLUDE_DIRS ${GFLAGS_INCLUDE_PATH} ${PROTOBUF_INCLUDE_DIRS})
+# Keep generic dependency prefixes after the selected Protobuf installation.
+# Otherwise a shared prefix can supply incompatible google/protobuf headers.
+set(BUTIL_INCLUDE_DIRS ${GFLAGS_INCLUDE_PATH})
 if(WITH_GLOG)
     find_path(GLOG_INCLUDE_PATH NAMES glog/logging.h)
     find_library(GLOG_LIB NAMES glog)
@@ -85,7 +87,8 @@ add_library(butil_build_config INTERFACE)
 target_link_libraries(butil_build_config INTERFACE brpc_common_config)
 target_compile_definitions(butil_build_config INTERFACE ${BUTIL_DEFINITIONS})
 target_include_directories(butil_build_config BEFORE INTERFACE
-    ${butil_generated_include_dir})
+    ${butil_generated_include_dir}
+    ${Protobuf_INCLUDE_DIRS})
 target_include_directories(butil_build_config INTERFACE ${BUTIL_INCLUDE_DIRS})
 
 set(butil_crc32c_options)

test/CMakeLists.txt

@@ -23,7 +23,9 @@ find_package(Gperftools)
 
 add_library(brpc_test_config INTERFACE)
 target_link_libraries(brpc_test_config INTERFACE brpc_build_config)
-target_include_directories(brpc_test_config INTERFACE ${CMAKE_CURRENT_BINARY_DIR})
+target_include_directories(brpc_test_config BEFORE INTERFACE
+    ${CMAKE_CURRENT_BINARY_DIR}
+    ${Protobuf_INCLUDE_DIRS})
 target_compile_definitions(brpc_test_config INTERFACE
     UNIT_TEST
     BVAR_NOT_LINK_DEFAULT_VARIABLES
@@ -253,6 +255,19 @@ target_link_libraries(test_butil PRIVATE
 
 add_test(NAME test_butil COMMAND test_butil)
 
+# The generic dependency intentionally contains an incompatible header at the
+# same path as a Protobuf header.  Compilation verifies that the include order
+# seen by the compiler selects the Protobuf package found for this build.
+add_library(protobuf_include_order_generic INTERFACE)
+target_include_directories(protobuf_include_order_generic INTERFACE
+    ${CMAKE_CURRENT_SOURCE_DIR}/protobuf_include_order/generic_include)
+add_executable(cmake_protobuf_include_order
+    ${CMAKE_CURRENT_SOURCE_DIR}/protobuf_include_order/protobuf_include_order.cpp)
+target_link_libraries(cmake_protobuf_include_order PRIVATE
+    brpc_test_config
+    protobuf_include_order_generic)
+add_test(NAME cmake_protobuf_include_order COMMAND cmake_protobuf_include_order)
+
 # test_bvar
 # -DBVAR_NOT_LINK_DEFAULT_VARIABLES not work for gcc >= 5.0, just remove the file to prevent linking into unit tests
 get_filename_component(bvar_default_variables

test/protobuf_include_order/generic_include/google/protobuf/stubs/common.h

@@ -0,0 +1,3 @@
+// This deliberately conflicts with the selected Protobuf installation.  The
+// compile probe must never see this header.
+#define GOOGLE_PROTOBUF_VERSION 1

test/protobuf_include_order/protobuf_include_order.cpp

@@ -0,0 +1,24 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information regarding copyright
+// ownership.  The ASF licenses this file to you under the Apache License,
+// Version 2.0 (the "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+// License for the specific language governing permissions and limitations
+// under the License.
+
+#include <google/protobuf/stubs/common.h>
+
+#if GOOGLE_PROTOBUF_VERSION == 1
+#error "A generic dependency's Protobuf header was selected"
+#endif
+
+int main() {
+    return 0;
+}