使用rcmp库编译C++钩子项目遇语法错误求助

错误信息 #

/root/lib-173/hook.cpp:14:77: error: expected constructor, destructor, or type conversion before ‘(’ token
 rcmp::hook_function<0x0809472A, int(gplayer_imp*, int, const void*, size_t)>([](auto original, gplayer_imp* self, int cmd_type, const void* buf, size_t size) {
                                                                             ^
/root/lib-173/hook.cpp:23:2: error: expected unqualified-id before ‘)’ token
 });

环境与代码 #

使用rcmp库进行函数钩子开发，相关代码如下：

hook.cpp #

#define CATCH_CONFIG_MAIN
#include "catch2/catch.hpp"

#include <rcmp.hpp>

#include <array>
 

struct gplayer_imp; 




rcmp::hook_function<0x0809472A, int(gplayer_imp*, int, const void*, size_t)>([](auto original, gplayer_imp* self, int cmd_type, const void* buf, size_t size) {
  
  if (cmd_type == 174 && size < 6) {
    
    return 0;
  }

 
  return original(self, cmd_type, buf, size);
});

CMakeLists.txt #

cmake_minimum_required(VERSION 3.16)
project(hook)


set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR x86_64)


set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)


set(SOURCE_FILES hook.cpp)


add_library(hook SHARED ${SOURCE_FILES})


target_compile_options(hook PRIVATE -std=c++17)


add_subdirectory(/root/lib-173/rcmp)


include_directories(/root/lib-173/rcmp/include)


target_link_libraries(hook PRIVATE rcmp)

问题分析与解决 #

核心问题 #

错误根源是全局作用域中直接匿名初始化rcmp::hook_function的语法不符合C++规范，同时lambda的签名需要匹配rcmp的要求。

修复步骤 #

1. 给hook_function实例命名：全局作用域不能直接创建临时对象并传递lambda，必须声明一个变量来持有这个hook实例：

   // 将原来的匿名声明改为带变量名的定义
   static auto my_hook = rcmp::hook_function<0x0809472A, int(gplayer_imp*, int, const void*, size_t)>(
       [](auto original, gplayer_imp* self, int cmd_type, const void* buf, size_t size) {
           if (cmd_type == 174 && size < 6) {
               return 0;
           }
           return original(self, cmd_type, buf, size);
       }
   );
   

   添加static避免全局变量的链接问题，也可根据需求调整。

2. 显式指定原函数类型（可选）：如果auto original推导存在问题，可以显式指定原函数类型消除歧义：

   using TargetFunc = int(gplayer_imp*, int, const void*, size_t);
   static auto my_hook = rcmp::hook_function<0x0809472A, TargetFunc>(
       [](rcmp::original_t<TargetFunc> original, gplayer_imp* self, int cmd_type, const void* buf, size_t size) {
           // ... 原有逻辑
       }
   );
   

3. 优化CMake配置：

   • 移除target_compile_options中的-std=c++17，因为CMAKE_CXX_STANDARD已经完成标准设置，避免重复配置
   • 确保rcmp子项目也使用C++17，在add_subdirectory前添加：

     set(CMAKE_CXX_STANDARD 17 PARENT_SCOPE)
     

最终修正后的hook.cpp核心片段 #

struct gplayer_imp; 

using TargetFunc = int(gplayer_imp*, int, const void*, size_t);

static auto my_hook = rcmp::hook_function<0x0809472A, TargetFunc>(
    [](rcmp::original_t<TargetFunc> original, gplayer_imp* self, int cmd_type, const void* buf, size_t size) {
        if (cmd_type == 174 && size < 6) {
            return 0;
        }
        return original(self, cmd_type, buf, size);
    }
);

内容的提问来源于stack exchange，提问作者Adriano Kramer