Am Freitag, dem 19.11.2021 um 13:13 +0000 schrieb Maxime Devos:
> Jonas Hahnfeld schreef op do 15-07-2021 om 20:44 [+0200]:
> > From 33af6a98c6801e7b4880d1d3f78f7e2097c2174e Mon Sep 17 00:00:00
> > 2001
> > From: Jonas Hahnfeld <hah...@hahnjo.de>
> > Date: Fri, 2 Jul 2021 23:03:17 +0200
> > Subject: [PATCH 2/3] Avoid matching calls of scm_gc_free
> >
> > There is no point in registering memory with the garbage collector
> > if it doesn't need to do its job. In fact, calling scm_gc_free in
> > a free function is wrong because it relies on Java finalization.
> >
> > * libguile/random.c (scm_c_random_bignum): Replace matching calls of
> > scm_gc_calloc and scm_gc_free.
> > * libguile/regex-posix.c (scm_make_regexp, regex_free): Avoid call
> > of scm_gc_free in free function.
> > * test-suite/standalone/test-smob-mark.c (make_x, free_x): Avoid
> > call of scm_gc_free in free function.
> > ---
> > THANKS | 1 +
> > libguile/random.c | 8 ++------
> > libguile/regex-posix.c | 6 +++---
> > test-suite/standalone/test-smob-mark.c | 4 ++--
> > 4 files changed, 8 insertions(+), 11 deletions(-)
> >
> > diff --git a/THANKS b/THANKS
> > index aa4877e95..786b65d1a 100644
> > --- a/THANKS
> > +++ b/THANKS
> > @@ -13,6 +13,7 @@ Contributors since the last release:
> > Volker Grabsch
> > Julian Graham
> > Michael Gran
> > + Jonas Hahnfeld
> > Daniel Hartwig
> > No Itisnt
> > Neil Jerram
> > diff --git a/libguile/random.c b/libguile/random.c
> > index 63da7f5d6..ac400a9fd 100644
> > --- a/libguile/random.c
> > +++ b/libguile/random.c
> > @@ -324,9 +324,7 @@ scm_c_random_bignum (scm_t_rstate *state, SCM m)
> > /* we know the result will be this big */
> > mpz_realloc2 (SCM_I_BIG_MPZ (result), m_bits);
> >
> > - random_chunks =
> > - (uint32_t *) scm_gc_calloc (num_chunks * sizeof (uint32_t),
> > - "random bignum chunks");
> > + random_chunks = (uint32_t *) scm_calloc (num_chunks * sizeof
> > (uint32_t));
> >
> > do
> > {
> > @@ -363,9 +361,7 @@ scm_c_random_bignum (scm_t_rstate *state, SCM m)
> > /* if result >= m, regenerate it (it is important to
> > regenerate
> > all bits in order not to get a distorted distribution) */
> > } while (mpz_cmp (SCM_I_BIG_MPZ (result), SCM_I_BIG_MPZ (m)) >=
> > 0);
> > - scm_gc_free (random_chunks,
> > - num_chunks * sizeof (uint32_t),
> > - "random bignum chunks");
> > + free (random_chunks);
>
> From the manual (about scm_gc_calloc & friends):
>
> ‘Memory blocks allocated this way may
> be released explicitly; however, this is not strictly needed, and we
> recommend _not_ calling ‘scm_gc_free’. All memory allocated with
> ‘scm_gc_malloc’ or ‘scm_gc_malloc_pointerless’ is automatically
> reclaimed when the garbage collector no longer sees any live reference
> to it(1).’
>
> As such, I'd recommend simply dropping the scm_gc_free
> (here and in other places), if the scm_gc_free was problematic
> because of Java finalization reasons.
We could, but what is the point of registering memory to the garbage
collector where we know it won't survive the function?
>
>
> > return scm_i_normbig (result);
> > }
> >
> > diff --git a/libguile/regex-posix.c b/libguile/regex-posix.c
> > index a08da02db..36bb639e0 100644
> > --- a/libguile/regex-posix.c
> > +++ b/libguile/regex-posix.c
> > @@ -67,7 +67,7 @@ static size_t
> > regex_free (SCM obj)
> > {
> > regfree (SCM_RGX (obj));
> > - scm_gc_free (SCM_RGX (obj), sizeof(regex_t), "regex");
> > + free (SCM_RGX (obj));
> > return 0;
> > }
> >
> > @@ -164,7 +164,7 @@ SCM_DEFINE (scm_make_regexp, "make-regexp", 1, 0,
> > 1,
> > flag = SCM_CDR (flag);
> > }
> >
> > - rx = scm_gc_malloc_pointerless (sizeof (regex_t), "regex");
> > + rx = scm_malloc (sizeof (regex_t));
>
> If the regex why scm_gc_malloc_pointerless -> scm_malloc?
> Is rx not pointerless?
Not sure I understand the question. We don't know what contents libc
will write into regex_t. It could be pointers which would be bad for
the garbage collector.
> You coud simply ...
>
>
> > - scm_gc_free (rx, sizeof(regex_t), "regex");
> > + free (rx);
>
> drop the scm_gc_free AFAIK.
No, I cannot as explained in the patch summary: If we use scm_gc_free
in a free function of a Smob, this relies on Java finalization because
the memory must not be reclaimed in the same cycle.
Jonas
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