32-bit LispWorks on x86 platforms maps its heap in one continuous block, and then grows upwards from the top. When it reaches a region that it cannot use, it can skip it. On Windows and Macintosh this skipping is safe, because LispWorks can safely detect regions of memory that it cannot use. On other x86 platforms, both the initial mapping and the furthur growing cannot safely detect when they overwrite some other code.
BaseAddress
(passed on command line with
--relocate-image
or as the second argument to
InitLispWorks
) tells LispWorks where to map the heap. On Windows and Macintosh, if the address is already used the heap will be mapped elsewhere. On other platforms, the mapping always works, and may destroy what is already mapped at that address.
ReserveSize
(passed on command line with
--reserve-size
or as the third argument to
InitLispWorks
) tells LispWorks how much additional memory to reserve. Reservation is properly supported on Windows and Macintosh, though the actual reserved size can be smaller if it fails to reserve as much as was requested. On platforms that do not support reservation (that is, not Windows or Macintosh), the reservation is done by using
mmap
with protection PROT_NONE.