On Thu, Aug 31, 2017 at 02:34:44PM -0700, Josh Triplett wrote:
> 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.
throw this in, perhaps?
diff --git a/validation/preprocessor/preprocessor23.c b/validation/preprocessor/preprocessor23.c
index 25be508..a778483 100644
--- a/validation/preprocessor/preprocessor23.c
+++ b/validation/preprocessor/preprocessor23.c
@@ -12,6 +12,9 @@ I(,)
I(x,)
I(,x)
I(x,x)
+#define J(...) ,##__VA_ARGS__
+J()
+J(x)
/*
* check-name: Preprocessor #23
* check-command: sparse -E $file
@@ -29,6 +32,7 @@ I(x,x)
,x
,x
,xx
+,x
* check-output-end
*
* check-error-start
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