bug#31750: simplify and tune Emacs stack-related allocation

[Daniel Colascione]

On 06/07/2018 07:27 PM, Paul Eggert wrote:
> While looking into the Emacs garbage collector's stack-overflow problems 
> I noticed several opportunities for improving performance and 
> simplifying the code in minor ways. I plan to install the attached 
> patches to take advantage of these opportunities; although they don't 
> address stack overflow,

One can also dream of the lisp evaluator doing escape analysis and stack 
allocation.

> they can be thought of as a first, cleanup step 
> toward addressing stack overflow.

Are you thinking along the same lines I was thinking of in my proposal 
to address GC safety?

> Overall these patches trim about 250 lines from the C source code, and 
> should improve efficiency by not creating objects on the heap to handle 
> stack-related events such as implementing save-excursion. This patch 
> also removes primitives like 'free_misc' that ask for trouble by 
> second-guessing the garbage collector. I'm filing this as a bug report 
> in order to give the patches a bit of time to cool before installing. 
> Comments welcome, as usual.