[PATCH] malloc: Deprecate hook variables, __default_morecore, <mcheck.h>

[Florian Weimer]

On 10/26/2016 05:55 PM, Joseph Myers wrote:
> On Wed, 26 Oct 2016, Florian Weimer wrote:
>
>> The functionality in <mcheck.h> will eventually be replaced with
>> no-op functions (and a separate, preloadable DSO).
>
> If you declare functionality deprecated then you need to update the manual
> accordingly.  But I don't think the right approach is to declare
> deprecated on an "eventually be replaced" basis.  Rather, the deprecation
> and the new DSO should be in the same patch series, going in the same
> glibc version, so the NEWS file and the main documentation can tell users
> of the mtrace script to preload the DSO and remove calls to the mtrace
> function (if that's the intended way to update code using mtrace and the
> one to be used for all the glibc tests that make use of it).

In my opinion, the larger ecosystem already provides suitable replacements.

* <mcheck.h> and all malloc hook functions are now deprecated.  Future
   implementations of the mcheck- and mtrace-related functions will not
   have any effect, and glibc will stop calling the hook functions from
   its malloc implementation.  Instead of mcheck and mtrace, developers
   should consider using valgrind.  As a replacement for the hook
   functions, developers can interpose their own malloc implementation.

Plus removal of the documentation of the hook functions from the manual 
(if there is anything left).

In any case, I'll submit a separate patch for documenting the malloc 
interposition feature (bug 20424).

Thanks,
Florian