One should never rely on the number of bytes actually allocated corresponding to the number requested.
The number of bytes allocated is guaranteed to be the same (or more? I guess it's rounded up to the page size when MP is enabled?) as requested, Malloc will return null if not.
The number of bytes allocated is guaranteed to be the same (or more? I guess it's rounded up to the page size when MP is enabled?) as requested, Malloc will return null if not.