bug#12450: Remove configure's --without-sync-input option.

[Paul Eggert]

On 09/15/2012 11:33 PM, Eli Zaretskii wrote:
>>>> -#ifdef REL_ALLOC
>>>> > >> -  malloc_hysteresis = 32;
>>>> > >> -#else
>>>> > >> -  malloc_hysteresis = 0;
>>>> > >> -#endif
>> > 
>> > malloc_hysteresis is used only by the non-SYNC_INPUT code.
> No, it is also used indirectly, via __malloc_extra_blocks, in
> gmalloc.c and in ralloc.c.

No, it is not used indirectly.  emacs_blocked_malloc is the only
function that uses malloc_hysteresis to set __malloc_extra_blocks.
And emacs_blocked_malloc is invoked only in the non-SYNC_INPUT code.

> But there's something I don't understand about this snippet.  Why does
> it set the value to 32 conditioned by REL_ALLOC ...

A nice property of removing the non-SYNC_INPUT code is that
we don't need to worry about cruft like that, because it's
not being used and we can remove it.