Article View: comp.bugs.misc
Article #87Re: Bug in dc? and another one?
From: Mike Wescott
Date: Wed, 07 Oct 1987 19:40
Date: Wed, 07 Oct 1987 19:40
40 lines
1775 bytes
1775 bytes
In article <1800@ncr-sd.SanDiego.NCR.COM> randall@ncr-sd.SanDiego.NCR.COM (0000-Randall Rathbun) writes:
> Running the short dc routine below to find the gcd of two numbers
> appears to work for small numbers.
>
> ........
>
> When r & s are about 100 digits or so in length, an error message appears:
> %Segmentation fault (core dumped)
>
> What is wrong?
Looks like an overflow of readstk. readstk has a hard coded limit of 100
in the SysVr3 source that I have access to. It's a bug in that the exceeding
the limit is not gracefully handled.
While tracking down this problem I came across some strange looking code:
In readc():
if((readptr != &readstk[0]) && (*readptr != 0)){
.
.
.
}
.
.
if(readptr != &readptr[0]){ <===== ???????????
readptr--;
.
.
.
Surely the author meant "if(readptr != &readstk[0]) ...
In anycase the whole if stmt gets optimized to nothing. Looks like the
relics of an attempt to put a more general file reading mechanism into dc.
-Mike Wescott
--
-Mike Wescott
wescott@ncrcae.Columbia.NCR.COM
Technical Details
Message-ID:
<930@sauron.Columbia.NCR.COM>Path:
arc1-ca.pugleaf.net!utzoo!mnetor!uunet!husc6!cmcl2!rutgers!gatech!hubcap!ncrcae!sauron!wescottReferences:
<1800@ncr-sd.SanDiego.NCR.COM>Show Full Headers
Complete Article Headers
Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!mnetor!uunet!husc6!cmcl2!rutgers!gatech!hubcap!ncrcae!sauron!wescott From: wescott@sauron.Columbia.NCR.COM (Mike Wescott) Newsgroups: comp.bugs.misc Subject: Re: Bug in dc? and another one? Message-ID: <930@sauron.Columbia.NCR.COM> Date: Wed, 7-Oct-87 15:40:31 EDT Article-I.D.: sauron.930 Posted: Wed Oct 7 15:40:31 1987 Date-Received: Sat, 10-Oct-87 10:34:07 EDT References: <1800@ncr-sd.SanDiego.NCR.COM> Reply-To: wescott@sauron.Columbia.NCR.COM (Mike Wescott) Organization: Entry Level Systems Development, NCR Corp., Columbia, SC Lines: 40 Keywords: dc, segmentation error