How to pass varargs arguments to 2nd function?

[antianti]

Hello,

I have a function that has a variable # of arguments of varying types.

int foo(short a, ...)
{
va_list argp
va_start(argp, a);
...
va_end(argp);
}

I want to be able to call another function, offering the same
variable list of arguments to it.

int bar(int a, ...)
{
va_list argp
va_start(short, a);
...
va_end(argp);
}

How could such a thing be done?

The function bar does not have to use the ... expression
if not doing so will help.

Thanks.

[Harald van =?UTF-8?b?RMSzaw==?=]

On Sun, 27 Jul 2008 13:58:00 -0700, antianti wrote:

Hello,

I have a function that has a variable # of arguments of varying types.

int foo(short a, ...)
{
va_list argp
va_start(argp, a);
...
va_end(argp);
}

I want to be able to call another function, offering the same variable
list of arguments to it.

How could such a thing be done?

The function bar does not have to use the ... expression if not doing so
will help.

You can make bar accept a va_list argument, and have bar use va_arg on
foo's list.

int bar(va_list argp)
{
/* ... */
}

int foo(short a, ...)
{
va_list argp;
va_start(argp, a);
bar(argp);
va_end(argp);
}

Consider taking a look at the vprintf (and related) library functions.
They are specifically there to be called this way as well.

[Robert Gamble]

On Jul 27, 4:58*pm, [e-mail] wrote:

Hello,

I have a function that has a variable # of arguments of varying types.

int foo(short a, ...)
{
* *va_list argp
* *va_start(argp, a);
*...
* *va_end(argp);

}

I want to be able to call another function, offering the same
variable list of arguments *to it.

int bar(int a, ...)
{
* *va_list argp
* *va_start(short, a);
*...
* *va_end(argp);

}

How could such a thing be done?

The function bar does not have to use the ... expression
if not doing so will help.

Thanks.

<http://c-faq.com/Question 15.12: <http://c-faq.com/varargs/
handoff.html>

--
Robert Gamble

[antianti]

I tried precisely what was in the FAQ and it didn't work with GNU CC.

Ah well, there is a solution: Pass a pointer to the location in the
stack where the varargs are located.

[Kenny McCormack]

In article <70**********************************@m73g2000hsh. googlegroups.com>,
<an******@rocketmail.comwrote:

>
I tried precisely what was in the FAQ and it didn't work with GNU CC.

Ah well, there is a solution: Pass a pointer to the location in the
stack where the varargs are located.

Beavis&Butthead: ork, ork, ork. He said "stack"...

[Ben Bacarisse]

an******@rocketmail.com writes:

I tried precisely what was in the FAQ and it didn't work with GNU
CC.

It does for me. Can you post an example of it not working? It is
possible there is a misunderstanding.

Ah well, there is a solution: Pass a pointer to the location in the
stack where the varargs are located.

Yuck. As a famous pig once said: "You're skate'n on thin ice, frog!".

--
Ben.

[Eric Sosman]

an******@rocketmail.com wrote:

I tried precisely what was in the FAQ and it didn't work with GNU CC.

Then either gcc has a rather serious bug, or your precision
isn't all it's cracked up to be. Not familiar with you but with
some experience of gcc, I incline toward the latter explanation.

Ah well, there is a solution: Pass a pointer to the location in the
stack where the varargs are located.

Oooog. There may be no such thing as the "worst possible"
solution, because any bad solution can most likely be made worse
by lavish application of additional error. "Worst possible" is
therefore a fictitious notion, something like the undescribable
singularity of a black hole. Our mathematics cannot cope with
the singularity, nor can our linguistic formalisms cope with
"worst possible." Still, we can safely say that your solution
is on the wrong side of the event horizon.

Oooog.

--
Eric Sosman
es*****@ieee-dot-org.invalid