Re: [PATCH 5/6] pass st.st_size as hint for strbuf_readlink()

[Jeff King <peff@peff.net>]

On Wed, Jul 25, 2018 at 08:41:00PM +0200, Torsten Bögershausen wrote:

> On Tue, Jul 24, 2018 at 06:51:39AM -0400, Jeff King wrote:
> > When we initially added the strbuf_readlink() function in
> > b11b7e13f4 (Add generic 'strbuf_readlink()' helper function,
> > 2008-12-17), the point was that we generally have a _guess_
> > as to the correct size based on the stat information, but we
> > can't necessarily trust it.
> > 
> > Over the years, a few callers have grown up that simply pass
> > in 0, even though they have the stat information. Let's have
> > them pass in their hint for consistency (and in theory
> > efficiency, since it may avoid an extra resize/syscall loop,
> > but neither location is probably performance critical).
> > 
> > Note that st.st_size is actually an off_t, so in theory we
> > need xsize_t() here. But none of the other callsites use it,
> > and since this is just a hint, it doesn't matter either way
> > (if we wrap we'll simply start with a too-small hint and
> > then eventually complain when we cannot allocate the
> > memory).
> 
> Thanks a lot for the series.
> 
>  For the last paragraph I would actually vote the other way around -
>  how about something like this ?
>  Note that st.st_size is actually an off_t, so we should use
>  xsize_t() here. In pratise we don't expect links to be large like that,
>  but let's give a good example in the source code and use xsize_t()
>  whenever an off_t is converted into size_t.
>  This will make live easier whenever someones diggs into 32/64 bit
>  "conversion safetyness"

I actually don't mind using xsize_t(), but if we're going into I think
we should do it consistently. I.e., as a patch on top with that
explanation.

-Peff