C++回调函数 [英] C++ call back function

问题描述

在为 CRYPTO_set_locking_callback 传递 C++ 回调函数时出现以下错误.

I get the following error when passing the C++ callback function for the CRYPTO_set_locking_callback.

Error C2664: 'CRYPTO_set_locking_callback' : cannot convert parameter 1 from
'void (__cdecl *)(int,int,char *,int)' to
'void (__cdecl *)(int,int,const char *,int)'
This conversion requires a reinterpret_cast, a C-style cast or
function-style cast

我的代码如下所示:

CRYPTO_set_locking_callback(&MyFunc::lock_callback);

void MyFunc::lock_callback(int mode, int type, char *file, int line)
{

    (void)file;
    (void)line;
    if (mode & CRYPTO_LOCK)
    {
        pthread_mutex_lock(&(lockarray[type]));
    }
    else
    {
        pthread_mutex_unlock(&(lockarray[type]));
    }
}

我尝试重新解释演员表，但没有运气，但不确定正确的做法是什么.任何帮助表示赞赏.

I tried reinterpret cast with no luck and not sure what is the correct way of doing it. Any help is appreciated.

推荐答案

根据错误信息，你的函数的第三个参数应该是一个 const char*:

According to the error message, your function's third argument is supposed to be a const char*:

void MyFunc::lock_callback(int mode, int type, const char* file, int line)

这应该不是问题，因为您甚至没有使用它.

This shouldn't be a problem, seeing as you're not even using it.

您也可以在文档中看到这一点:

You can see this in the documentation, too:

void CRYPTO_lock(int mode, int n, const char *file, int line);

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