Hey! Thanks for the offer and thanks for the correction. I've revisited relevant threads and it seems that it is indeed -O0 because things are slower with higher optimization levels (I must have misremembered).
```
the optimization level -O0 is used because higher optimization
levels seem to interfere with the binaryen options needed to get the
garbage collector to work correctly and tend slow down the program
(might be worth experimenting with the optimization options)
```
Relevant links: https://gitlab.com/embeddable-common-lisp/ecl/-/merge_reques... https://github.com/ivmai/bdwgc/issues/650
Most notably an entry in the INSTALL file:
``` the optimization level -O0 is used because higher optimization levels seem to interfere with the binaryen options needed to get the garbage collector to work correctly and tend slow down the program (might be worth experimenting with the optimization options) ```