Re: [PATCH] Add internal-only port structure; move iconv descriptors there

[ludo@gnu.org (Ludovic Courtès)]

Mark H Weaver <mhw@netris.org> skribis:

> ludo@gnu.org (Ludovic Courtès) writes:
>
>> Mark H Weaver <mhw@netris.org> skribis:
>>
>>> I've come to the conclusion that it is not safe to modify 'scm_t_port'
>>> in 2.0 at all; not even to change the member names.  In brief, the
>>> reason has to do with the C11 standard definition of "compatible types",
>>> which ties into the strict aliasing rules.  Section 6.2.7 of C11 spells
>>> out what it means for two structures declared in separate translation
>>> units to be compatible, and among other things their member names must
>>> be the same.
>>
>> I can’t imagine how changing the *name* of a member could change
>> something to the structure’s layout in practice.
>
> It doesn't change the structure's layout.  However, it could cause
> link-time optimization to break our code.

Ah right, makes sense.

>>> +#define scm_gc_typed_calloc(t) ((t *) scm_gc_calloc (sizeof (t), #t))
>>
>> Not really convinced by this, but hey.  Ideally, this would need to go
>> in the manual too.
>
> Maybe talk to Andy about it?  It was his suggestion.

No big deal.

Ludo’.