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Re: Enlarge MAX_ALLOCA?
From: |
Eli Zaretskii |
Subject: |
Re: Enlarge MAX_ALLOCA? |
Date: |
Thu, 19 Jun 2014 19:48:06 +0300 |
> From: David Kastrup <address@hidden>
> Date: Thu, 19 Jun 2014 18:23:26 +0200
>
> Eli Zaretskii <address@hidden> writes:
>
> > -#define SAFE_ALLOCA(size) ((size) < MAX_ALLOCA \
> > +#define SAFE_ALLOCA(size) ((size) <= MAX_ALLOCA \
> > ? alloca (size) \
> > : (sa_must_free = true, record_xmalloc (size)))
> >
> > @@ -4469,7 +4469,7 @@ extern void *record_xmalloc (size_t) ATT
> >
> > #define SAFE_ALLOCA_LISP(buf, nelt) \
> > do { \
> > - if ((nelt) < MAX_ALLOCA / word_size) \
> > + if ((nelt) <= MAX_ALLOCA / word_size) \
> > (buf) = alloca ((nelt) * word_size); \
> > else if ((nelt) < min (PTRDIFF_MAX, SIZE_MAX) / word_size) \
> > { \
>
> Bad idea to change < to <= here.
The original macros were inconsistent: some used < and some <=, so I
changed them.
> If there is a hard limit due to short offsets or similar (and if
> there weren't, why bother at all?), then allocating a full 64kB
> might be a bad idea.
Is there really such a system? If so, which one? And why would that
be a worse idea than to allocate the same 64KB off the heap (which is
what that macro does in the 'else' clause? What am I missing?
> 64kB feels arbitrary.
I explained my rationale for choosing this value.
Re: Enlarge MAX_ALLOCA?, Stefan Monnier, 2014/06/19
Re: Enlarge MAX_ALLOCA?, Dmitry Antipov, 2014/06/20
Re: Enlarge MAX_ALLOCA?, Eli Zaretskii, 2014/06/20