Re: read() MAX_IO_SIZE bytes, more than SSIZE_MAX?

[Joachim Schmitz <jojo@schmitz-digital.de>]

Junio C Hamano <gitster <at> pobox.com> writes:

> 
> On Sat, Feb 7, 2015 at 12:32 PM, Torsten Bögershausen <tboegi <at> 
web.de> wrote:
> > I don't know every platform of the planet well enough to be helpful 
here,
> > especially the ones which don't follow all the specifications.
> >
> > In other words: As long as we can not guarantee that SSIZE_MAX is 
defined,
> > (and is defined to somethong useful for xread()/xwrite() )
> > we should be more defensive here:
> >
> > tweak only on platform where we know it is needed and we know that it 
works.
> 
> Yup, I agree that is a sensible way to go.
> 
>  (1) if Makefile overrides the size, use it; otherwise
>  (2) if SSIZE_MAX is defined, and it is smaller than our internal
> default, use it; otherwise
>  (3) use our internal default.
> 
> And leave our internal default to 8MB.
> 
> That way, nobody needs to do anything differently from his current build 
set-up,
> and I suspect that it would make step (1) optional.
> 

something like this:

/* allow overwriting from e.g. Makefile */
#if !defined(MAX_IO_SIZE)
# define MAX_IO_SIZE (8*1024*1024)
#endif
/* for plattforms that have SSIZE and have it smaller */
#if defined(SSIZE_MAX && (SSIZE_MAX < MAX_IO_SIZE) 
# undef MAX_IO_SIZE /* avoid warning */
# define MAX_IO_SIZE SSIZE_MAX
#endif

Steps 2 and 3 only , indeed step 1 not needed...

Bye, Jojo