[RFC] how to get the size of a malloc(9) block ?

[Luigi Rizzo]

On Mon, Dec 2, 2013 at 4:36 AM, jb <jb.1234abcd at gmail.com> wrote:

>  <dt71 <at> gmx.com> writes:
>
> >
> > So new flags could be [1]:
> > - realloc_flags(p, s, REALLOCF_NO_MOVE)
> > ...
> > - realloc_flags(p, s, REALLOCF_NO_MOVE | REALLOCF_ELASTIC)
> > ...
> > For this, there could be a REALLOCF_FORCE flag
>
> In case of realloc_flags() failing the request, to avoid unnecessary
> followups with regular realloc() when desired, we should include an option
> like REALLOCF_FALLBACK_ANY that would allow to fallback on the regular
> realloc() logic, in one call.
>
> In addition, because I have an impression that realloc_flags() may have
> a future as a replacement for regular realloc() and we should aim for it,
> we should include an option like REALLOCF_ANY for that purpose.
>
> So far, the options could be as follows:
> - realloc_flags(p, s, option)
>   where option is one or a combination (where appropriate) of:
>   REALLOCF_ANY                - default (move or no-move; regular
> realloc())
>   REALLOCF_NO_MOVE            - no-move
>   REALLOCF_ELASTIC            - combined with REALLOCF_NO_MOVE
>   REALLOCF_FORCE              - combined with REALLOCF_NO_MOVE
>   REALLOCF_FALLBACK_ANY       - combined with REALLOCF_NO_MOVE or its
>                                 derivatives like REALLOCF_ELASTIC, etc
>

just five ? for a (quote) "clean, safe and maintainable API",
I'd probably also add a few more, such as
REALLOCF_ALWAYS to trigger bugs on bad assumptions in the code,
REALLOCF_I_AM_FEELING_LUCKY for the newbies, and
REALLOCF_REAL_PROGRAMMERS_NEVER_DO_THAT_I_WILL_PANIC
for skilled folks.

I am not sure they are enough to cover the spectrum
of possible options, but there are at least 32 bits
in the flags so we have a few more left.

cheers
luigi