Re: [PATCH v5 1/2] semihosting/arm-compat: replace heuristic for softmmu SYS_HEAPINFO

[Peter Maydell]

On Mon, 21 Feb 2022 at 17:06, Alex Bennée <alex.bennee@linaro.org> wrote:
>
>
> Peter Maydell <peter.maydell@linaro.org> writes:
>
> > On Thu, 10 Feb 2022 at 11:30, Alex Bennée <alex.bennee@linaro.org> wrote:
> >>
> >> The previous numbers were a guess at best and rather arbitrary without
> >> taking into account anything that might be loaded. Instead of using
> >> guesses based on the state of registers implement a new function that:
> >>
> >>  a) scans the MemoryRegions for the largest RAM block
> >>  b) iterates through all "ROM" blobs looking for the biggest gap
> >>
> >> The "ROM" blobs include all code loaded via -kernel and the various
> >> -device loader techniques.
> >>
> >> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> >> Cc: Andrew Strauss <astrauss11@gmail.com>
> >> Cc: Keith Packard <keithp@keithp.com>
> >> Message-Id: <20210601090715.22330-1-alex.bennee@linaro.org>
> >>
> >
> >
> >> +/*
> >> + * Sort into address order. We break ties between rom-startpoints
> >> + * and rom-endpoints in favour of the startpoint, by sorting the 0->1
> >> + * transition before the 1->0 transition. Either way round would
> >> + * work, but this way saves a little work later by avoiding
> >> + * dealing with "gaps" of 0 length.
> >> + */
> >> +static gint sort_secs(gconstpointer a, gconstpointer b)
> >> +{
> >> +    RomSec *ra = (RomSec *) a;
> >> +    RomSec *rb = (RomSec *) b;
> >> +
> >> +    if (ra->base == rb->base) {
> >> +        return ra->se - rb->se;
> >> +    }
> >> +    return ra->base > rb->base ? 1 : -1;
> >> +}
> >
> > This sort comparator still doesn't report the equality
> > case as actually equal.
>
> When ra->se and rb->se are the same it returns 0. Is that not what you want?

Oops, yes it does. I misread it because I was expecting it to be
structured differently. (AFAIK there is no "standard" way to
structure a comparator-function that works with multiple fields,
so the way you have it is fine.)

-- PMM