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From: pattis@cs.washington.edu (Richard Pattis)
Subject: Re: "Subtract C, add Ada"
Message-ID: <D1x0Iy.GEL@beaver.cs.washington.edu>
Summary: Here is documentation of a real == error in C
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References: <D1Msq8.4Hs@inmet.camb.inmet.com> <862035D1F1C@annwfn.com>
Date: Thu, 5 Jan 1995 04:30:16 GMT
Date: 1995-01-05T04:30:16+00:00
List-Id: <comp.lang.ada>

In article <862035D1F1C@annwfn.com> merlin@annwfn.com (Fred McCall) writes:
>In <D1Msq8.4Hs@inmet.camb.inmet.com> mg@asp.camb.inmet.com Mitch Gart writes:
>
>>Ada leaves less room for single-keystroke
>>errors, such as the common C error of using = (assignment) instead of
>>== (comparison); 
>
>I've always been curious.  Just *where* is this a "common C error"?
>I've seen lots of beginners and non-C programmers claim it is, but I
>don't recall ever hearing of anyone who knew what they were doing (and
>who was using a real tool -- say, lint -- to check their code) making
>it. 

In Peter van der Linden's excellent book, "Expert C Programming: Deep C
Secrets", Prentice Hall, on page xx (that's 20 in the preface) he describes
a problem from 1993 in the Operating System development group at SunSoft
(he works at Sun and was part of the debugging effort he describes). A bug
in the asynchronous I/O libary was holding up a $20million dollar sale - the
customer needed the library to work. It turns out that someone had written
x==2 by accident. As van der Linden states

"Some versions of the lint program would have detected this problem, but it's
all too easy to avoid the automatic use of this essential tool."

Rich
-- 
------------------------------------------------------------------------------
  Richard E. Pattis                     "Programming languages are like
  Looking for a Job                      pizzas - they come in only "too"
					 size: too big and too small.