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

[Alex Bennée]

Peter Maydell <peter.maydell@linaro.org> writes:

> 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.)

The other options were all ugly ;-)

-- 
Alex Bennée