Number: 768

Date: 18-Apr-84 17':26':21

Submitter: Sannella.PA

Source: Masinter

Subject: Document CAR/CDRERR

Lisp Version: 

Description: '
Date': 11 Apr 84 20':37 PST'
From': JonL.pa'
Subject': MTBF on CAR/CDRERR'
To': Masinter'
cc': LispSupport, JonL.pa'
'
I can''t go for more than about 30 seconds.  Until the bugs in INFILECOMS? and the CLISPWORD props are fixed, I''ve no hope of generating more of the CAR/CDRERR errors because I can''t run long enough to get beyond these.'
'
-----'
'
Date': 17 Apr 84 15':56 PST'
From': masinter.pa'
Subject': Re': MTBF on CAR/CDRERR'
In-reply-to': JonL.pa''s message of 11 Apr 84 20':37 PST'
To': JonL.pa'
cc': LispCore^, LispSupport.pa'
'
BTW, I added a ''hack'' to the ufns for CAR and CDR which might allow us to still ''error'' on illegal CARs and CDRs in the case where they would otherwise yield infinite loops':'
'
CAR/CDRERR=NIL, T act as before'
'
any other value, e.g., (SETQ CAR/CDRERR ''ONCE), then'
'
attempt to take CAR or CDR of a string causes an error'
attempt to take CAR or CDR of any other non-NIL non-LISTP returns the string "{cxr of non-list}" as before.'
'
This gives a one-shot, which takes care of a lot of the careless ones, but disallows loops. '
'
This isn''t meant as a long-term solution, but allows one to work long enough with CAR/CDRERR set on to get some work done.'
'
Once we can survive long enough with this flag set on, we can track down the more frequent errors too.'
'
OVERFLOW(T) is reportedly working reasonably lately, btw.'
'
-----'
'
Date': 24 Jun 84 20':38 PDT'
From': JonL.pa'
Subject': [Acuff.pa': Re': CAR/CDRERR]'
To': LispSupport.pa'
cc': JonL.pa, Masinter.pa'
'
I thought there was an AR for this one; if there is, I should also be attn''d.  Looks like we have two things to do':'
  1) fix more places in the system that crash when CAR/CDRERR is T'
  2) document CAR/CDRERR'
'
-- JonL --'
     ----- Begin Forwarded Messages -----'
'
Date': 24 Jun 84 19':41 PDT'
From': Acuff.pa'
Subject': Re': CAR/CDRERR'
In-reply-to': JonL.pa''s message of 24 Jun 84 19':26 PDT'
To': JonL.pa'
cc': Acuff.pa, Stansbury.pa'
'
   I just looked through the "Interlisp-D Specifics" section and I found no mention of CAR/CDRERR.  I also looked near CAR and CDR documentation, and around error handling sections.  It really doesn''t seem to be in there.'
'
-- Rich'
'
     ----- End Forwarded Messages -----'
'
From': masinter.pa'
Date': 25-Jun-84  1':54':49 PDT'
Subject': Re': [Acuff.pa': Re': CAR/CDRERR]'
In-reply-to': JonL''s message of 24 Jun 84 20':38 PDT'
To': JonL'
cc': LispSupport, Masinter, Acuff'
'
I hadn''t intended to document it until you could do something with it besides crash.'
'


Workaround: 

Test Case: 

Edit-By: masinter.PA

Edit-Date: 20-Jul-84 14':16':46

Attn: Documentation

Assigned To: 

In/By: 

Disposition: [this is a FIX not a bug. I changed status to Fixed, Attn to Release.]

System: Language Support

Subsystem: Storage Formats/Mgt

Machine: 

Disk: 

Microcode Version: 

Memory Size: 

File Server: 

Server Software Version: 

Difficulty: Moderate

Frequency: Everytime

Impact: Serious

Priority: Hopefully

Status: Open

Problem Type: Documentation

Source Files: