Variable argument functions

[ChimpFace9000]

I wrote a variable argument function(va function) that requires at least one string. Then i wrote another va function that requires at least one string. How do i pass all the arguments that get passed to the second va function in a call to the first.

like...

void one(cont char* fmt, ...)
{
}

void two(const char* fmt, ...)
{
one(fmt, ...);
}

[abdul]

I don't think there is any way other passing them manually 1 by 1.

[ChimpFace9000]

Well how do i do that?

[parksie]

#include <iostream>
#include <cstdarg>

using namespace std;

void two(int count, va_list va) {
	for(int i = 0; i < count; ++i) {
		cout << va_arg(va, int) << endl;
	}
}

void one(int count, ...) {
	va_list args;

	va_start(args, count);
	two(count, args);	
}

VC++7, Win2000.

[ChimpFace9000]

That doesnt answer my question at all.

[parksie]

Ummm....you wanted to pass all the provided arguments?

The va_list syntax is an alternative method of passing a variable number of arguments.

[parksie]

For amusement: http://www.eskimo.com/~scs/C-faq/q15.13.html

[HarryW]

Originally posted by parksie

#include <iostream>
#include <cstdarg>

using namespace std;

void two(int count, va_list va) {
	for(int i = 0; i < count; ++i) {
		cout << va_arg(va, int) << endl;
	}
}

void one(int count, ...) {
	va_list args;

	va_start(args, count);
	two(count, args);	
}

VC++7, Win2000.

Don't you need a va_end() ?

[parksie]

Probably. Apparently all it does is reset the pointer to NULL, so I don't think it's that critical on x86 systems.

That said, even though it compiled and ran perfectly on mine, it should have been in there.

[CornedBee]

But, parksie, this way you can't call two with variable arguments anymore. The compiler won't allow it.

This should work:

#include <iostream>
#include <cstdarg>

using namespace std;

void two_inner(int count, va_list va) {
	for(int i = 0; i < count; ++i) {
		cout << va_arg(va, int) << endl;
	}
}

void one(int count, ...) {
	va_list args;

	va_start(args, count);
	two_inner(count, args);	
}

void two(int count, ...) {
	va_list args;

	va_start(args, count);
	two_inner(count, args);	
}

You can take a look at all the *printf CRT functions and _output (if you have the source) and note the similarities to parksie's and my code.

BTW the source of sprintf shows how to create a fake FILE that makes stream functions write to a memory buffer. You must be extremly careful using it though.