This is only a problem on 32 bit platforms, but this code has been like this for forever so we don't know why it works.

From [~stuefe]:

I'm not sure the alignment handling is correct. Either that or I don't understand the contract of the Amalloc... functions.

I thought:

Amalloc(x) -> allocate x bytes, align returned pointer to 64bit
AmallocWords(x) -> allocate x bytes, align returned pointer to pointer size
?

Because the functions just align the given byte size (well, Amalloc() aligns automatically, AmallocWords() asserts). But that has no effect on the returned pointer.

Consider this sequence, on 32bit:

AmallocWords(4) -> _hwm = 4
Amalloc(8) -> will return a pointer to offset 4, so not 64bit aligned.