[M3commit] CVS Update: cm3

[Rodney M. Bates]

Tony Hosking wrote:
> I am tracking down this bug right now (trying to get a 64-bit  
> AMD64_DARWIN port) up and running.  If you have something as a  testcase 
> that will demonstrate the problem I would appreciate it.

Attached.  It doesn't write any output.  I just used m3gdb to go in and
print variables at various times.  Line 16 is enough to show the problem.
I also used m3cgcat, where the problem also shows.

Where things go wrong is in TInt.ToInt, line 65:


PROCEDURE ToInt (READONLY r: Int;  VAR x: INTEGER): BOOLEAN =
   VAR sign := CheckSign (r, BITSIZE (INTEGER) DIV BITSIZE (IByte)); (* <=== line 65, HERE. *)
   BEGIN
     (* ensure the result has the right sign extension *)
     CASE sign OF
     | Sign.Bad => RETURN FALSE;
     | Sign.Pos => x := 0;
     | Sign.Neg => x := Word.Not (0);
     END;

     (* finally, pack the bits *)
     FOR i := r.n-1 TO 0 BY -1  DO
       x := Word.Or (LShift (x, BITSIZE (IByte)), r.x[i]);
     END;

     RETURN TRUE;
   END ToInt;

The value gets through all the stages OK to here, with r.n=8, but the 2nd
actual parameter to CheckSign is 4, and CheckSign thinks the value is
negative and within the range of INTEGER.  I think just passing r.n to
CheckSign would be right, but there are lots of calls on ToInt that I
haven't looked at, so for a quick fix, I did the hack at the relevant call
site in M3CG_BinWr.


> 
> On Apr 11, 2008, at 5:08 PM, Rodney M. Bates wrote:
> 
>> CVSROOT:    /usr/cvs
>> Changes by:    rodney at birch.    08/04/11 17:08:38
>>
>> Modified files:
>>     cm3/m3-sys/m3middle/src/: M3CG_BinWr.m3
>>
>> Log message:
>>     Fix a bug that caused, e.g., 16_80000000L and 16_000000008000000L
>>     to be converted to 16_ffffffff8000000L.  This is something of a
>>     low hack at a call site on TInt.ToInt.  Probably, the fix should
>>     be pushed inside TInt.ToInt, but all the calls thereon need to be
>>     reviewed before doing this.
> 
> 
> 

-- 
-------------------------------------------------------------
Rodney M. Bates, retired assistant professor
Dept. of Computer Science, Wichita State University
Wichita, KS 67260-0083
316-978-3922
rodney.bates at wichita.edu
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