Dan writes:
>
> I32 CA I16V
> dbineqv:=DBINARY(dasciieqv,length);
>
> If dbineqv is an element of a double array, the condition code of the call
> appears to sometimes get corrupted. It never seems to happen otherwise.
>
> I believe this might be because SPL may be doing pointer fixup math on the
> double array and therefore invalidating the condition code. If this is truly
> the case, then my guess is it's possible for this to happen with any
> intrinsic which returns an I32 (although I have not yet tested this).
>
> Can anyone confirm this? Is it a bug or a feature? >BD
It's a feature. SPL isn't doing pointer fixup math, it's the fault of
the (presumed) loading of the index of your array. If the index is a
variable, not a constant, then SPL emits code something like:
LDX DB 001
The LDX instruction, like all loads from memory, sets the condition code
to indicate something useful. In the case of 16/32 bit loads, the condition
code is set to reflect the sign of the value (negative, zero, positive).
The basic problem is that most users assume that condition codes are set
only by procedures ... in fact, you can argue that procedures never set
the condition code at all! Instead, the exiting of a procedure (via the
EXIT instruction) *restores* the condition code to the value that it had
at the instant the PCAL instruction was executed. The poor little EXIT
instruction has no idea that the programmers of DBINARY, FOPEN, or any
other intrinsic that sets the condition code, actually went out of their
way to change the saved value of the condition code in the stack marker!
So, here's a solution to your problem:
double
temp'd;
temp'd := dbinary (...);
if <> then
...
dbineqv := temp'd;
Here's an example test program:
begin
double array
matrix (0 : 9);
integer
inx,
len;
logical array
buf (0 : 39);
byte array
buf' (*) = buf;
intrinsic
dascii,
dbinary,
print;
len := move buf' := "123";
$control innerlist
inx := 2;
matrix (inx) := dbinary (buf', len); ! "incorrect" example
<<------------------------------------------------
00015 DZRO, NOP 000700 01.05
00016 LOAD DB 004 041004 02.65
00017 LOAD DB 002 041002 02.65
00020 PCAL,000 000000 14.90
00021 LDX DB 001 131001 02.65
^^^^^^^^^^^^^
00022 STD DB 000,I,X 167000 04.40
------------------------------------------------->>
$control nolist ! can't say: $control noinnerlist :(
if < then
print (buf, - move buf' := "got ccL", 0)
else if > then
print (buf, - move buf' := "got ccG", 0)
else
begin
len := move buf' := "ok, got: ";
len := len + dascii (matrix (2), 10, buf' (len));
print (buf, -len, 0);
end;
end.
--
Stan Sieler [log in to unmask]
http://www.allegro.com/sieler.html
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