Mikael G found that we're missing parentheses in the is_size_aligned_ macro (soon to be renamed is_aligned):
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I looked through this and I think it looks good but I think you may need to add some extra brackets around the use of the parameters in is_size_aligned_

change
#define is_size_aligned_(size, alignment) ((size) == (align_size_up_(size, alignment)))

to
#define is_size_aligned_(size, alignment) ((size) == (align_size_up_((size), (alignment))))
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