Tamas Rudnai wrote:
>> Not CBLOCK (more or less as "bad" as EQU).
>> Use the RES directive only.
>
> It's less as bad as you cannot put two variables into the same
> location :-)

Yes it is, precisely because you CAN create multiple symbols with the same
value.  If your code assumes these symbols each stand for separate RAM
locations, you've got a bug.

Again, CBLOCK is for creating enumerated assembly time constants.  For
example:

  cblock 0                   ;define the color IDs
         color_red
         color_grn
         color_blu
    endc

  cblock 0                   ;define command IDs
         cmd_nop             ;no operation
         cmd_setname         ;set the unit's name string
         cmd_hcf             ;halt and catch fire
    endc

COLOR_GRN and CMD_SETNAME have the same value of 1.  This is a perfectly
legal and reasonable use of CBLOCK.  However note that this has absolutely
nothing to do with RAM allocation.  Only the RES (reserve) directive does
that.

If a attempt is made to define multiple variables at the same address, it
will get caught.  For example, if in one module you write:

ram1    udata   h'40'
counter  res     1
myval    res     2

and then in another module:

ram2    udata   h'42'
newval   res     1
morestuff res    1

the assembler won't have a problem, but the linker will detect the overlap
and fail.  In this case you are attempting to put the second byte of MYVAL
at the same address as the first byte of NEWVAL.  Actually the linker sees
that the absolute sections .RAM1 and .RAM2 overlap, but the point is that
the system won't let you accidentally allocate two variables at the same
memory location.


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