c++ - How to wrap a function with variable length arguments?

Question

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

I came across Variable Length Arguments but this suggests a solution with Python & C using libffi.

Now, if I want to wrap printf function with myprintf

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 
this is a character: %c and 
 another number: %d
",a, v, b);
    return 0;
}

But the results are not as expected!

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

Any point where did I miss??

Answer 1

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.)

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 
this is a character: %c and 
 another number: %d
",a, v, b);
    return 0;
}