Fix stackalloc in a loop introduced by #32025

[MihaZupan]

Fixes #32374, fixes #32367

[davidfowl]

This feels like an analyzer warning... Though of course there are cases where it would be fine.

[MihaZupan]

@jkotas I was not aware that using stackalloc in a loop is a mistake.

Why is that so?

[jkotas]

This feels like an analyzer warning

Yes, it was noted in #30740

I was not aware that using stackalloc in a loop is a mistake.

It allocates a new chunk of memory every time it is executed. The memory is released only once the method exits.

[stephentoub]

Do we know why it only affected macOS? Are our default stack sizes different? Do we align or size stackallocs differently? Etc.

[jkotas]

Yes, the default stack sizes differ between different OSes.

[stephentoub]

Yes, the default stack sizes differ between different OSes.

My surprise is that I was under the impression Linux (most distros) was significantly larger than Windows. This suggests macOS is significantly smaller.

Just looking it up now, seems the default size on macOS is indeed 512K.

[jkotas]

Yep, it is not the first time that this came up. E.g.: #12088 (comment)