如何包装长度可变参数的函数？ [英] How to wrap a function with variable length arguments?

问题描述

我希望做这在C / C ++。

I am looking to do this in C/C++.

我遇到 可变长度参数 但是这表明了一个解决方案蟒蛇和放大器;下使用 libffi 。

现在，如果我想换行的printf 函数 myprintf

Now, if I want to wrap printf function with myprintf

我要做的就是象下面这样：

What I do is like below:

void myprintf(char* fmt, ...)
{
    va_list args;
    va_start(args,fmt);
    printf(fmt,args);
    va_end(args);
}

int _tmain(int argc, _TCHAR* argv[])
{
    int a = 9;
    int b = 10;
    char v = 'C';
    myprintf("This is a number: %d and \nthis is a character: %c and \n another number: %d\n",a, v, b);
    return 0;
}

但结果并不如预期！

But the results are not as expected!

This is a number: 1244780 and
this is a character: h and
another number: 29953463

任意点在哪里我想念??

Any point where did I miss??

推荐答案

的问题是，你不能用'的printf'与va_args。您必须使用 vprintf 如果您使用的是可变的参数列表。 vprint，vsprintf中，vfprintf等（也有安全的版本在微软的C运行时，将prevent缓冲区溢出等）

the problem is that you cannot use 'printf' with va_args. You must use vprintf if you are using variable argument lists. vprint, vsprintf, vfprintf, etc. (there are also 'safe' versions in Microsoft's C runtime that will prevent buffer overruns, etc.)

您样品的工作原理如下：

You sample works as follows:

void myprintf(char* fmt, ...)
{
    va_list args;
    va_start(args,fmt);
    vprintf(fmt,args);
    va_end(args);
}

int _tmain(int argc, _TCHAR* argv[])
{
    int a = 9;
    int b = 10;
    char v = 'C'; 
    myprintf("This is a number: %d and \nthis is a character: %c and \n another number: %d\n",a, v, b);
    return 0;
}

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