Alignment issue in mi_malloc_aligned when requested size = alignment (regression on dev-slice)

[epoupon]

Hello,

We recently tried to bump mimalloc from 1.7.9 to 2.0.9.
However we noticed a regression in mi_malloc_aligned when size = alignment for the following values: 256, 512, 1024 (all other values down to 8 and up to 1MB are correctly handled though).
Tests done on windows using Visual Studio 2022, MI_PADDING and MI_DEBUG are not set.

I've just started using mimalloc, so I'm not familiar enough with the code to say for certain yet, but...
The comment says that 'small sized allocations are naturally aligned'. I'm not sure what a 'small sized allocation' is in this case. Is that 128 or 1024? Cause that's exactly the difference here.

In mi_heap_malloc_aligned, is that supposed to say MI_SMALL_WSIZE_MAX instead of MI_SMALL_SIZE_MAX in those ifs?
That would at least solve the issue, and it'd be an easy mistake to make.

It's either that, or somewhere else it's wrong the other way around where the segments ended up being underaligned because they're using MI_SMALL_WSIZE_MAX instead of MI_SMALL_SIZE_MAX. This might actually be the more likely case, based on the naming

Maybe @daanx knows?

[daanx]

Wow, that was a terrible bug; :-( Should be fixed in the latest dev-slice -- Thanks so much for the report!