Number: 1291

Date:  1-Jun-84 12':57':53

Submitter: Sannella.PA


Subject: LOG is trashing its argument when it is a floatp

Assigned To: 


Status: Closed

In/By: Carol

Problem Type: Bug

Impact: Serious

Difficulty: Easy

Frequency: Everytime

Priority: Hopefully

System: Language Support

Subsystem: Arithmetic

Machine: 1132


Lisp Version: 

Source Files: 

Microcode Version: 

Memory Size: 

File Server: 

Server Software Version: 

Disposition: '
["Sannella.PA" "20-Aug-84 17':09':41" Status':(Fixed->Closed) In/By':]

Description: Date': 18 May 84 01':21 PDT'
Subject': Arithmetic SHOWSTOPPER!!'
To': Sannella, Raim.pasa'
cc': Sheil,JonL, vanMelle, LispSupport'
Three horrible bugs have come to my attention in the past two days, whose combined weight almost force a new loadup for Carol.  Focus is in LLFLOAT and AARITH files.'
2) LOG trashes it''s argument -- random RPLACD strikes again; now fixed in new version of AARITH.'
2) LOG is trashing its argument when it is a floatp.  Apparently, this one has been around since January, but it will have very serious  consequences, and will be extremely hard for customers to find; thus my feeling that this one, alone, is a showstopper.  The problem stems from trying to copy a floatp by doing (FPLUS X 0.0) -- the compiler "optimizes" this out to a call to FLOAT, which just returns X without copying it.  This actually is a reasonable optimization, but there is no documented way to get a copy of a floatp; after talking this over with Larry, we decided to put a new "function" in the system -- \FLOAT.BOX -- which will open-compile into the shortest way to copy a floatp.  This won''t be available until the next loadup, so tentatively I changed the FPLUS to a PLUS, which *currently* does cause a copying.  [Thanks to Kelly, who helped Kris track this one to the case of EXPT on two floatps]'


Test Case: 

Edit-By: Sannella.PA

Edit-Date: 20-Aug-84 17':09':44