Creating a va_list

[P. Hari Krishna]

Hi,
I have a situation where I do not know the number of arguments I pass to a
function at compile time.
So is there any way, that we can programmaticall y create a "va_list" and then
pass it to the function that can the use to do some sprintfs ?

Thanks
-Hari

[Eric Sosman]

Re: Creating a va_list

P. Hari Krishna wrote:[color=blue]
> Hi,
> I have a situation where I do not know the number of arguments I pass to a
> function at compile time.
> So is there any way, that we can programmaticall y create a "va_list" and then
> pass it to the function that can the use to do some sprintfs ?[/color]

No; there is no portable way to construct an argument
list at run-time. Every function call has a fixed number
of arguments.

I'm not sure what you're trying to do, but perhaps
the vsprintf() function might be of use.

--
Eric.Sosman@sun .com

[Kieran Simkin]

Re: Creating a va_list

"P. Hari Krishna" <hkpammiNoSpam@ NoSpamgmail.com > wrote in message
news:pan.2004.0 9.08.09.19.22.1 28732@NoSpamgma il.com...[color=blue]
> Hi,
> I have a situation where I do not know the number of arguments I pass to a
> function at compile time.
> So is there any way, that we can programmaticall y create a "va_list" and
> then
> pass it to the function that can the use to do some sprintfs ?[/color]

Unless I've completely misunderstood your question, surely it'd make sense
to just use one argument - a pointer to a NULL terminated array of (possibly
void) pointers? -- or two arguments if you're not sure at compiletime the
type of the data you're passing to your function. Or is the problem that you
need to pass an unknown number of arguments to a varargs function that has
been defined by someone other than you? -- if this is the case, I don't
believe it's possible in standard C, although it may be possible with some
machine-specific ASM.


~Kieran Simkin
Digital Crocus

http://digital-crocus.com/

[Moonie]

Re: Creating a va_list


void function( char *ptr, ... )
{
va_list args;
char format[81];

va_start( args, ptr );
vssprintf( format, ptr, args );
va_end( args );
}

the moral of the story is that ptr must be in a format for sprintf
for example: "%d%c%s" etc. and format must be the length of the string
that you expect.

Marc Smith.....Mooni e



--
Moonie
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[Moonie]

Re: Creating a va_list


vssprint should be vsprintf

so sorry about that.

Marc Smith.....Mooni e



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Moonie
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Posted via http://www.codecomments.com
------------------------------------------------------------------------

[P. Hari Krishna]

Re: Creating a va_list

On Wed, 08 Sep 2004 10:29:17 -0400, Eric Sosman wrote:
[color=blue]
> P. Hari Krishna wrote:[color=green]
>> Hi,
>> I have a situation where I do not know the number of arguments I pass to a
>> function at compile time.
>> So is there any way, that we can programmaticall y create a "va_list" and then
>> pass it to the function that can the use to do some sprintfs ?[/color]
>
> No; there is no portable way to construct an argument
> list at run-time. Every function call has a fixed number
> of arguments.
>
> I'm not sure what you're trying to do, but perhaps
> the vsprintf() function might be of use.[/color]
The arguments are in the form of a list (or an array of pointers to
strings)and so I cannot know the number of arguments at compile time.
But I think I have got the solution (portable). All I have in the
formatting string is only a bunch of %s, so I wrote a small sprintf-like
function that will go and parse the formatting string for %s and form
the resulting buffer, manually.

Thanks anyway.
-Hari