[HarfBuzz] [Feature Request] Custom allocator support
Behdad Esfahbod
behdad.esfahbod at gmail.com
Sat Oct 3 05:20:15 PDT 2015
On 15-10-02 10:00 PM, Jamie Dale wrote:
> That's similar to what I originally had, so I'm fine with something like that.
> My only question is, what would hb_malloc_impl, hb_calloc_impl,
> hb_realloc_impl, and hb_free_impl be defined to in your example?
Define it to the name of your external function. I don't want to fix a name
in HarfBuzz itself. Updated patch to add externs:
diff --git a/src/hb-private.hh b/src/hb-private.hh
index 07550cb..826e41a 100644
--- a/src/hb-private.hh
+++ b/src/hb-private.hh
@@ -54,6 +54,23 @@
#include <stdarg.h>
+/* Compile-time custom allocator support. */
+
+#if defined(hb_malloc_impl) \
+ && defined(hb_calloc_impl) \
+ && defined(hb_realloc_impl) \
+ && defined(hb_free_impl)
+extern void* hb_malloc_impl(size_t size);
+extern void* hb_calloc_impl(size_t nmemb, size_t size);
+extern void* hb_realloc_impl(void *, size_t size);
+extern void hb_free_impl(void *ptr);
+#define malloc hb_malloc_impl
+#define calloc hb_calloc_impl
+#define realloc hb_realloc_impl
+#define free hb_free_impl
+#endif
+
I'll go ahead and commit this. Let me know if it doesn't work.
> I went with the extern function approach so I could inject my own allocator
> functions into HarfBuzz at link time, rather than have to include any of our
> code into HarfBuzz at compile time (since any local code changes we make have
> to be re-applied against new versions).
>
> For your reference, this was my original implementation:
>
> /* Override the allocation functions when
> * HAVE_EXTERNAL_ALLOCATOR is defined. */
> #ifdef HAVE_EXTERNAL_ALLOCATOR
> extern void* _hb_malloc(size_t);
> extern void* _hb_calloc(size_t, size_t);
> extern void* _hb_realloc(void*, size_t);
> extern void _hb_free(void*);
> #define malloc _hb_malloc
> #define calloc _hb_calloc
> #define realloc _hb_realloc
> #define free _hb_free
> #endif
>
> Failure to define those functions in something that linked to HarfBuzz would
> produce an unresolved external symbol error at link time.
>
> -Jamie.
>
> On 2 October 2015 at 08:08, Behdad Esfahbod <behdad.esfahbod at gmail.com
> <mailto:behdad.esfahbod at gmail.com>> wrote:
>
> Hi Jamie,
>
> I'm opposed to runtime custom allocators, but am fine with something like what
> you suggest. However, that has two down sides:
>
> 1. It touches a lot of callsites,
>
> 2. I have to add macros to make sure stock malloc etc are not used by
> mistake.
>
> If doing 2., I might as well just define them to their custom behavior. Ie,
> would this patch work for you:
>
> diff --git a/src/hb-private.hh b/src/hb-private.hh
> index 07550cb..167c067 100644
> --- a/src/hb-private.hh
> +++ b/src/hb-private.hh
> @@ -54,6 +54,19 @@
> #include <stdarg.h>
>
>
> +/* Compile-time custom allocator support. */
> +
> +#if defined(hb_malloc_impl) \
> + && defined(hb_calloc_impl) \
> + && defined(hb_realloc_impl) \
> + && defined(hb_free_impl)
> +#define malloc hb_malloc_impl
> +#define calloc hb_calloc_impl
> +#define realloc hb_realloc_impl
> +#define free hb_free_impl
> +#endif
> +
> +
> /* Compiler attributes */
>
>
>
>
> On 15-09-30 03:49 PM, Jamie Dale wrote:
> > Since there was no movement here I went ahead and hacked in our allocator by
> > redefining malloc, calloc, realloc, and free to point to extern'd functions
> > that I define in our application. This yielded some performance benefits for
> > us, so I'm hoping that a more standard HarfBuzz solution might appear at
> some
> > point :)
> >
> > If you're not keen on the idea of allowing the allocator to be swapped
> out at
> > runtime, would you at least allow it to be extern'd at compile time? I'm not
> > familiar with HarfBuzz coding standards, but I'd propose adding
> something like
> > a HAVE_EXTERNAL_ALLOCATOR define to control this, and then define your own
> > allocator functions that you'd use in place of malloc, etc.
> >
> > Basically, something like this (I currently have this code in
> hb-private.hh):
> >
> > /* Define our allocation functions. These may be provided by an
> > * external source when HAVE_EXTERNAL_ALLOCATOR is defined. */
> > #ifdef HAVE_EXTERNAL_ALLOCATOR
> > extern void* _hb_malloc(size_t);
> > extern void* _hb_calloc(size_t, size_t);
> > extern void* _hb_realloc(void*, size_t);
> > extern void _hb_free(void*);
> > #define hb_malloc _hb_malloc
> > #define hb_calloc _hb_calloc
> > #define hb_realloc _hb_realloc
> > #define hb_free _hb_free
> > #else
> > #define hb_malloc malloc
> > #define hb_calloc calloc
> > #define hb_realloc realloc
> > #define hb_free free
> > #endif
> >
> > You'd then replace calls to malloc, calloc, realloc, and free from within
> > HarfBuzz to use hb_malloc, hb_calloc, hb_realloc, and hb_free.
> >
> > This is basically the code I already have, except I
> > redefined malloc, calloc, realloc, and free rather than create the
> > hb_*variants, as I didn't want to change too much HarfBuzz code.
> >
> > Thoughts?
> >
> > On 31 August 2015 at 22:17, Jamie Dale <jamiedale88+harfbuzz at gmail.com <mailto:jamiedale88%2Bharfbuzz at gmail.com>
> > <mailto:jamiedale88+harfbuzz at gmail.com <mailto:jamiedale88%2Bharfbuzz at gmail.com>>>
> wrote:
> >
> > Hey,
> >
> > I'm not sure if this is correct place to post/discuss feature requests...
> > hopefully it is.
> >
> > Our project makes use of a custom memory allocator, and we like to ensure
> > that our third-party libraries are using this where possible, as our
> > allocator can offer significantly better performance, and can also allow
> > us better memory profiling and debugging support.
> >
> > A look through the HarfBuzz source code would suggest that it doesn't
> > currently support custom memory allocators, and instead just directly
> > calls the standard malloc/free/etc functions. I was wondering if you'd
> > ever considered (or would consider) adding a way to override this behaviour?
> >
> > In my case, I'd just need a single global override to be set before my
> > first call to any other HarfBuzz code... basically something like
> > the FT_Memory struct from FreeType:
> > http://www.freetype.org/freetype2/docs/reference/ft2-system_interface.html#FT_Memory
> >
> > Thanks,
> > Jamie.
> >
> >
> >
> >
> > _______________________________________________
> > HarfBuzz mailing list
> > HarfBuzz at lists.freedesktop.org <mailto:HarfBuzz at lists.freedesktop.org>
> > http://lists.freedesktop.org/mailman/listinfo/harfbuzz
> >
>
>
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