Visual Studio __VA_ARGS__问题 [英] Visual studio __VA_ARGS__ issue

问题描述

我运行cl/P test.cpp，文件和结果如下.

I run cl /P test.cpp, the file and result is as following.

test.cpp

#define FiltedLog( ...) \
    if (logDetail) \
        MP_LOG(LOG_INFO,  __VA_ARGS__);

#define MP_LOG(level,fmt,...) \
    BOOAT::LOG("MP", level, fmt, ##__VA_ARGS__)

#define LOG(tag,level,fmt,...) \
    Log::log(tag, level, "%s: " fmt, __PRETTY_FUNCTION__, ##__VA_ARGS__)

int main ()
{
     FiltedLog ( "abc", 1, 2);
}

Cl/P test.cpp:

Cl /P test.cpp :

#line 1 "test.cpp"

int main ()
{
     if (logDetail) BOOAT::Log::log("MP", LOG_INFO, "%s: " "abc", 1, 2, __PRETTY_FUNCTION__ );;
}

我想知道为什么将__PRETTY_FUNCTION__作为结果的最后一个参数. 我认为结果应该是:

I wonder why the __PRETTY_FUNCTION__ are put as the last arguments in the result. I assume the result should be:

 if (logDetail) BOOAT::Log::log("MP", LOG_INFO, "%s: " "abc", __PRETTY_FUNCTION__, 1, 2);;

这是VS 2010的错误吗?

Is it an bug of VS 2010?

推荐答案

是的，这是Visual C ++预处理器中的一个长期存在的错误.要解决此问题，请使用间接寻址:

Yes, this is a longstanding bug in the Visual C++ preprocessor. To work around it, use indirection:

#define INDIRECT_EXPAND(m, args) m args

#define FiltedLog( ...) \
    if (logDetail) \
        INDIRECT_EXPAND(MP_LOG, (LOG_INFO, __VA_ARGS__));

(请注意，__PRETTY_FUNCTION__是Visual C ++不支持的非标准扩展.)

(Do note that __PRETTY_FUNCTION__ is a nonstandard extension that is not supported by Visual C++.)

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