Re: Lisp-level macro to avoid excessive GC in memory-allocating code

[Stefan Monnier]

>> Is this aligned with what the implementation of the Lisp interpreter
>> actually does?  I'm not sure we know, where we allocate memory for
>> Lisp data, whether we are going to bind some variable to the produced
>> data.  Thus "count recent allocations within the current sexp" sounds
>> like non-trivial to implement.

That's also my impression.

> I am not 100% sure, but AFAIK lisp interpreter always knows the current
> lisp nesting level.

Not really, no.  There is some related info, but that's a non-trivial
part of the cost of interpretation so any increase to that info will
tend to slow us down.

A simple `with-mostly-allocating-code` macro that increases
`gc-cons-percentage` to 1.0 sounds a lot simpler and won't impose any
extra burden on "normal" code.


        Stefan