[PATCH 2/2] Avoid crashes when system libraries use the purgeable zone allocator

[Justin Lebar]

+        * [...] This
+        * obviously fails when the default zone is the jemalloc zone, so
+        * malloc_default_purgeable_zone is called beforehand so that the
+        * default purgeable zone is create when the default zone is still
+        * a scalable_zone.

Nit: s/create/created

+        * As purgeable zones only exist on >= 10.6, we need to check for the
+        * function existence at runtime.

Nit: s/function/function's

On Tue, Mar 27, 2012 at 5:20 AM, Mike Hommey <mh+jemalloc at glandium.org> wrote:
> From: Mike Hommey <mh at glandium.org>
>
> ---
>  src/zone.c |   21 +++++++++++++++++++++
>  1 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/src/zone.c b/src/zone.c
> index 4b6c75e..d5eae46 100644
> --- a/src/zone.c
> +++ b/src/zone.c
> @@ -3,6 +3,13 @@
>  #  error "This source file is for zones on Darwin (OS X)."
>  #endif
>
> +/*
> + * The malloc_default_purgeable_zone function is only available on >= 10.6.
> + * We need to check whether it is present at runtime, thus the weak_import.
> + */
> +extern malloc_zone_t *malloc_default_purgeable_zone(void)
> +JEMALLOC_ATTR(weak_import);
> +
>  /******************************************************************************/
>  /* Data. */
>
> @@ -207,6 +214,20 @@ register_zone(void)
>  #endif
>  #endif
>
> +       /*
> +        * The default purgeable zone is created lazily by OSX's libc. It uses
> +        * the default zone when it is created for "small" allocations
> +        * (< 15 KiB), but assumes the default zone is a scalable_zone. This
> +        * obviously fails when the default zone is the jemalloc zone, so
> +        * malloc_default_purgeable_zone is called beforehand so that the
> +        * default purgeable zone is create when the default zone is still
> +        * a scalable_zone.
> +        * As purgeable zones only exist on >= 10.6, we need to check for the
> +        * function existence at runtime.
> +        */
> +       if (malloc_default_purgeable_zone)
> +               malloc_default_purgeable_zone();
> +
>        /* Register the custom zone. At this point it won't be the default. */
>        malloc_zone_register(&zone);
>
> --
> 1.7.9.1
>
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