On Wed, Sep 19, 2007 at 12:46:04PM +0000, Edgar Toernig wrote:
> Pierre Habouzit wrote:
> >
> > +void strbuf_addvf(struct strbuf *sb, const char *fmt, va_list ap)
> > +{
> > + int len;
> > +
> > + len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
> > + if (len < 0) {
> > + len = 0;
> > + }
> > + if (len > strbuf_avail(sb)) {
> > + strbuf_grow(sb, len);
> > + len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
> > + if (len > strbuf_avail(sb)) {
> > + die("this should not happen, your snprintf is broken");
> > + }
> > + }
> > + strbuf_setlen(sb, sb->len + len);
> > +}
>
> The second vsnprintf won't work as the first one consumed all args
> from va_list ap. You need to va_copy the ap. But iirc va_copy poses
> compatibility issues. Unless va_copy is made available somehow,
> I would suggest to let the caller know that the buffer was too small
> (but isn't any more) and it has to call the function again:
That's what I thought, and then nfvasprintf in trace.c suffers from
the same issue, as I copied the code from there.
> do {
> va_start(ap, fmt);
> again = strbuf_addvf(sb, fmt, ap);
> va_end(ap);
> } while (again);
in fact doing it twice is enough but either way I don't like to impose
that to the caller :/ I mean it's totally stupid to have to do that on a
strbuf. of course we could provide a macro doing that ...
--
·O· Pierre Habouzit
··O madcoder@xxxxxxxxxx
OOO http://www.madism.org
Attachment:
pgp4QXlnVIINn.pgp
Description: PGP signature
