bug#22086: 25.1.50; [PATCH] Integrate the musl hybrid malloc patch for elf systems

[Ken Brown <kbrown@cornell.edu>]

On 12/20/2015 11:06 PM, Rich Felker wrote:
> On Sun, Dec 20, 2015 at 10:37:24PM -0500, Ken Brown wrote:
>> On 12/20/2015 5:33 PM, Paul Eggert wrote:
>>> While thinking over this patch I'd like to propose what should be a
>>> simpler approach. This new proposal is more radical, and so should not
>>> be applied to the emacs-25 branch, but it should make the port to musl
>>> etc. automatic.
>>>
>>> The simpler approach is to remove gmalloc.c, and to use the system
>>> memory allocator, i.e., to behave as if SYSTEM_MALLOC is defined on all
>>> platforms.
>>>
>>> We can still support hybrid malloc for Cygwin, if SYSTEM_MALLOC wouldn't
>>> work on Cygwin for some reason; and we can support the similar hybrid on
>>> Darwin, if it's still needed.
>>
>> SYSTEM_MALLOC doesn't work on Cygwin, largely because Cygwin's
>> malloc doesn't support malloc_set_state and malloc_get_state.  There
>> may be other problems too.  (It's been a while since I tried it.)
>
> I don't see how this is possible; malloc_[gs]et_state do not exist on
> other systems either. Presumably this is some hack needed for the
> dumper, which wouldn't be needed if malloc weren't used pre-dumping.

You're right.  I wasn't thinking clearly.  But several years ago, before 
Cygwin started putting the heap in high memory, there were still issues 
that made it impossible to use the system malloc.  I've forgotten the 
details.

Ken