On Thu, Aug 31, 2017 at 10:09:22PM +0100, Al Viro wrote:
> On Thu, Aug 31, 2017 at 09:54:33PM +0100, Al Viro wrote:
> > What a mess... Note that for non-vararg it *is* the right interpretation
> > (with #define A(x) [x] we will have A() interpreted as "empty token sequence
> > as the only argument", not "no arguments given"). For vararg case we
> > normally do not need to distinguish "not given" and "empty" - the only
> > thing that cares is exactly the ,## kludge. There with
> > #define B(x,...) [x,##__VA_ARGS__]
> > B(1) and B(1,) yield [1] and [1,] resp. And for everything other than
> > "just ..." we even get it right...
> >
> > I see what's going on there; will post a fix in a few.
>
>
> Fix macro argument parsing for (...) case
>
> Nasty corner case for the sake of ,##__VA_ARGS__ perversion - for something
> like #define A(x,...) [x,##__VA_ARGS] we want A(1) to expand to [1] and
> A(1,) - to [1,]. In other words, "no vararg given" and "vararg empty" are
> different and need to be distinguished. Unfortunately, in case when there
> was nothing but vararg we got it wrong - #define A(...) ,##__VA_ARGS ended
> up with A() interpreted as "one empty argument" (as it would in non-vararg
> case) rather than "zero arguments".
>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> diff --git a/pre-process.c b/pre-process.c
> index 74414df..8800dce 100644
> --- a/pre-process.c
> +++ b/pre-process.c
> @@ -296,9 +296,11 @@ static int collect_arguments(struct token *start, struct token *arglist, struct
> for (count = 0; count < wanted; count++) {
> struct argcount *p = &arglist->next->count;
> next = collect_arg(start, p->vararg, &what->pos, p->normal);
> - arglist = arglist->next->next;
> if (eof_token(next))
> goto Eclosing;
> + if (p->vararg && wanted == 1 && eof_token(start->next))
> + break;
> + arglist = arglist->next->next;
> args[count].arg = start->next;
> args[count].n_normal = p->normal;
> args[count].n_quoted = p->quoted;
This looks plausible; we should also add a test for it, though.
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