Re: BLOCK_INPUT in compile_pattern_1

[Stefan Monnier <monnier@iro.umontreal.ca>]

>    Here's another reason to avoid allocation: Emacs 
>    processes input from X in a signal handler; processing X input may
>    call malloc; if input arrives while a matching routine is calling
>    malloc, then we're scrod.  But Emacs can't just block input while
>    calling matching routines; then we don't notice interrupts when
>    they come in.  So, Emacs blocks input around all regexp calls
>    except the matching calls, which it leaves unprotected, in the
>    faith that they will not malloc.  */

> But I think that reason is obsolete.  Nowadays regex.c defines malloc
> as a macro to expand into xmalloc, which does BLOCK_INPUT.

> So I think that that BLOCK_INPUT call is obsolete,
> and that so is MATCH_MAY_ALLOCATE.

> Do you think this is correct?

I guess so, although to tell you the truth, avoiding such brittle
reasoning (And code) was one of the motivations for my SYNC_INPUT patch, so
now that I've implemented this patch I prefer not to think too much about
what could happen in this or that corner case when SYNC_INPUT is
not used.


        Stefan