C++ 如果静态函数在单独的文件中声明，如何将其作为回调传递？

如何解决C++ 如果静态函数在单独的文件中声明，如何将其作为回调传递？

上下文

在类 Utils 的单独文件中，有两个静态函数：quote_sql() 和 default_callback()。如果直接调用，这两个函数都可以正常工作。但是，如果您将 default_callback() 作为指向 sqlite3_exec 的指针传递，它将不会被调用。

代码

// sqlite_common.hpp
class Utils {
    
public:
    static std::string quote_sql(const std::string str)
    {
        std::string quote = "'";
        std::string result = quote + str + quote;
        return result;
    }

    static int default_callback(void* used,int argc,char** argv,char** azColName)
    {
        std::cout << "Callback is called.\n";
        bool* status = static_cast<bool*>(used);
        *status = true;

        for(int i = 0; i < argc; i++)
        {
            printf("%s = %s\n",azColName[i],argv[i] ? argv[i] : "NULL");
        }

        std::cout << "\n";
        return 0;
    }
};

// main.cpp
void signup_func()
{
    // quote_sql() is working as it should
    std::string sql = 
        "INSERT INTO User (Login,Password) VALUES (" 
        +  Utils::quote_sql(login) + "," + Utils::quote_sql(password) + ");";
    
    // here default callback is never called even when it should have been
    char* zErrMsg; 
    bool status = false; // status is just the first argument of callback
    int rc = sqlite3_exec(db,sql.c_str(),Utils::default_callback,&status,&zErrMsg);
    
    // however this will output "Callback is called."
    default_callback(0,0);

    // this also doesn't work
    auto callback = &Utils::default_callback;
    int rc = sqlite3_exec(db,callback,&zErrMsg);

    // declaring default_callback outside of a class doesn't work either
    // in fact that's how it was in the first place
    // the only case when it works is when I define callback in main.cpp
}

我想要什么？

我希望能够将 default_callback() 存储在一个单独的文件中，并将其传递给程序周围的函数，并在它应该执行的地方执行。

编辑

这段代码以某种方式工作。类似情况：静态回调函数在一个单独的文件中，通过指针传递但工作正常。

// main.cpp

#include <iostream>

#include "callback.hpp"

int do_action(int a,int b,int(*action)(int,int))
{
    return action(a,b);
}

int main()
{
    auto callback = &sum;
   
    // will output 4 as it should
    std::cout << do_action(2,2,callback) << "\n";

    return 0;
}

// callback.hpp

static int sum(int a,int b)
{
    return a + b;
}