ISO Pascal reference manual

Chapter 6
byte-aligned, is allocated for each variable; if they both lie in the range
-32768..32767, a 2-byte word is allocated, aligned on a 2-byte boundary;
otherwise a 4-byte doubleword is allocated, aligned on a 4-byte boundary.
Record
The structure of a record is a function of the types of its fields. In general a
simple field in a record will be aligned as specified in the descriptions above,
relative to the start of the record. The record as a whole will be aligned on a
4-byte boundary, and the total size of the record is always rounded up by
the compiler to be a multiple of 4 bytes. A field of a record which is itself a
record will follow the same rules (recursively). Note that the keyword
PACKED has no effect at all (in the Pascal compiler described, Version
2.2.4), hence the structure and alignment requirements of a packed record
are the same as for a non-packed one. Records having variant sections are
implemented in such a fashion that the variant having the largest overall
size determines the total allocated size of the record; this is true even when
the heap allocation mechanism, NEW, is used with the tags of the variant
selectors being provided. This latter point may change in a future version of
the Pascal system, however.
Pointer
Pointers occupy 32 bits, aligned on a 4-byte address boundary. There are no
unusual points to observe about their use, other than that when Pascal code
is compiled with assignment checks, every access via a pointer is checked, to
ensure that (a) the pointer is not NIL, and (b) that it points to a block of
heap memory previously allocated by the Pascal NEW mechanism. In
consequence of check (b), any Pascal code which interfaces to another
language system, or Panos, where pointers are imported via the interface,
should be compiled with these checks turned off; otherwise the program is
liable to fail on check (b), since a foreign pointer will not in general satisfy
this condition. A pointer is foreign if it occurs either as a parameter to an
exported Pascal procedure or function, or as the result of an imported
non-Pascal function.
34 Pasca] Issue 1