🚀 go-pugleaf

In article <434pa4$c4c@news1.wing.net>, pgf@american.com (Paul G. Fox)
writes: 
<snip>
|> the question is this:
|> 
|> must the usage of
|> 	foo = va_arg(ap, type_of_foo);
|> be confined to the same routine in which the 
|> 	va_list ap;
|> and
|> 	va_start(ap, last_fixed_arg);
|> expansions occur?

No. The standard explicitly says you can pass "ap" to a function.

|> 
|> or, can i pass "&ap" to a lower level routine where it's
|> declared like this:
|> 	va_list *app
|> and used as:
|> 	bar = va_arg(*app, type_of_bar)

The standard does not mention passing &ap. But it says you _can_ pass ap (but
if you call va_arg on that, the original ap, i.e. the ap in the original
function becomes unusable till a va_end).

I believe in the absence of explicit statement, your use should be allowed,
and the original ap should still be usable.

|> 
|> the code i have does the latter, i.e. it passes a pointer to "ap" to
|> the lower level routine.  [the reason is that the top routine which is
|> actually called with variable arguments farms out work to lower level
|> routines, but they want to do their work on the original variable list.]
|> 
|> this particular vendor's stdarg.h, however, contains:
|> 	typedef char   *va_list[1];
|> instead of the more typical
|> 	typedef char   *va_list;
|> 
|> the vendor's introduction of array semantics causes my "&ap" to break.

I do not understand this. In what context does a fully paranthesized
expression `(*&a)' differ from `a' if `a' is an addressable lvalue?

I believe this set of parantheses in the definition of va_arg is mandatory. 

Cheers
Tanmoy
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