Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!udel!princeton!pucc!EGNILGES
From: EGNILGES@pucc.Princeton.EDU (Ed Nilges)
Newsgroups: comp.lang.c
Subject: Interesting Bug in Microsoft C
Message-ID: <12541@pucc.Princeton.EDU>
Date: 4 Mar 91 19:42:49 GMT
Reply-To: EGNILGES@pucc.Princeton.EDU
Organization: Princeton University, NJ
Lines: 18
Disclaimer: Author bears full responsibility for contents of this article

A colleague wrote a program containing the value -2,147,483,648L (-2**31)
which compiled and ran on Borland Turbo-C but produced a diagnostic "con-
stant to long" on Microsoft QuickC.  When he changed it, replacing
the value with -2,147,483,647L - 1 the program ran on QuickC.

I think what is happening is this.  The compiler is evaluating con-
stants in the lexical analysis phase by (in the case of -2**31) not-
ing the sign, then grabbing each decimal digit, shifting the old
value by multiplying by ten, and adding the next digit to the old
value.  This algorithm has a bug.  It generates the value 2**31 which
is too large for a long integer.

I'm sure that others have bumped into this bug, soooo...


     1.  Is this diagnosis correct?

     2.  If so, when will Microsoft fix this problem?