[libdispatch-dev] failed assertions when DISPATCH_DEBUG enabled

Robert Watson robert at fledge.watson.org
Mon Dec 28 03:29:54 PST 2009

On Wed, 23 Dec 2009, Martin Nowack wrote:

> On Tuesday 22 December 2009 06:06:28 am Mark Heily wrote:
>> When I define DISPATCH_DEBUG=1 and build the library under Linux, almost
>>  all of the test programs fail. I checked a couple of them, and they both
>>  fail a dispatch_assert() test at the same place: in
>>  _dispatch_ccache_init().
> The reason is that the current implementation of malloc_zone for linux 
> (src/shims/malloc_zone.h) is just a dummy implementation and returns always 
> a null-pointer. Therefore, this assertion will always fail.
> The current dummy implementation just dispatches the zone_malloc calls to 
> the normal malloc routine. The attached "patch" circumvents the problem with 
> the assertion by allocating a zone and returning a pointer to it. The 
> behavior of the zone_malloc remains the same.

Hi Martin--

I've committed a slight variation on this patch as r176: specifically, I 
return (void *)-1 rather than malloc'ing state.  As we don't implement the
internals of malloc zones, I would rather cause a segfault if a consumer of 
the API decides to muck around with the internals, as that implies more 
support for malloc zones than the stubs provide.  Could you let me know if 
this adequately addresses the assertion failures you've been running into?

Robert N M Watson
Computer Laboratory
University of Cambridge

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