Re: last_marked array is now ifdef'ed away

[Mattias Engdegård]

12 sep. 2024 kl. 11.19 skrev Eli Zaretskii <eliz@gnu.org>:

>> Commit 7a8798de95a5 (from Apr 4 2022) made the last_marked[] array and
>> the related machinery of tracing the marked objects #ifdef'ed away by
>> default:
>> 
>>  +/* Whether to remember a few of the last marked values for debugging.  */
>>  +#define GC_REMEMBER_LAST_MARKED 0

Yes, debugging code in the inner loop of one of the hottest paths of the GC 
probably shouldn't be on by default. I've done a large amount of intricate GC 
debugging and never felt a need for it, but it is easy enough to enable when 
wanted.

We could hitch it to another existing config option like ENABLE_CHECKING, or 
even make this an independent config option, but there's value in not having to 
reconfigure and recompile everything when turning it on so keeping it localised 
in the source seems the better choice.

We could also change the `#if` to `if` to reduce the risk of bitrot. I'll do 
that later.