126 lines
5.7 KiB
HTML
126 lines
5.7 KiB
HTML
<!--startcut ==========================================================-->
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
|
|
<HTML>
|
|
<HEAD>
|
|
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
|
|
<META NAME="GENERATOR" CONTENT="Mozilla/4.07 [en] (X11; I; Linux 2.0.36 i686) [Netscape]">
|
|
<META NAME="Author" CONTENT="James M. Rogers">
|
|
<META NAME="Description" CONTENT="This article is the sixth in a series designed to explore the Standard C library implementation available for Linux">
|
|
<META NAME="Keywords" CONTENT="linux, standard c library, character functions">
|
|
<META NAME="Classification" CONTENT="Second Year Programming">
|
|
<TITLE>The Standard C Library for Linux Issue 41</TITLE>
|
|
</HEAD>
|
|
<BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#0000AF"
|
|
ALINK="#FF0000">
|
|
<!--endcut ============================================================-->
|
|
|
|
<H4>
|
|
"Linux Gazette...<I>making Linux just a little more fun!</I>"
|
|
</H4>
|
|
|
|
<P> <HR> <P>
|
|
<!--===================================================================-->
|
|
|
|
<CENTER>
|
|
<H1>
|
|
<FONT COLOR="#800000">The Standard C Library for Linux</FONT></H1></CENTER>
|
|
|
|
<CENTER>
|
|
<H3>
|
|
<FONT COLOR="#000080">Part Six: <assert.h> Diagnostics for Programmers</FONT></H3></CENTER>
|
|
|
|
<CENTER>
|
|
<H4>
|
|
By <A HREF="mailto:jrogers@u.washington.edu">James M. Rogers</A></H4></CENTER>
|
|
|
|
<HR>
|
|
<P>The last article was on <stdlib.h> Standard Library. This article
|
|
is on <assert.h> Diagnostics for Programmers.
|
|
<P>I am assuming a knowledge of c programming on the part of the reader.
|
|
There is no guarantee of accuracy in any of this information nor suitability
|
|
for any purpose.
|
|
<P>If used properly assertions will allow programmers to much more easily
|
|
document and debug your code with no impact on runtime performance.
|
|
Assertions are not meant to be used for production code as they cause the
|
|
program to terminate with an error condition. Since assertions are
|
|
never to be used in production code they are not useful in finding runtime
|
|
errors such as a failure to allocate memory. You must still handle
|
|
failed return conditions of all function calls the same as always.
|
|
<P>Instead, what assertions allow you to do is document the assumptions
|
|
that you make as you program and allow you to debug the obvious logic errors
|
|
that you have made. As you program around these logic errors you
|
|
can modify your assertions to not die on errors that you are now handling.
|
|
<P>The example is <A HREF="rogers_example06.c">rogers_example06.c</A>
|
|
. In this program I will demonstrate the use of assertions by using
|
|
a simple program that asks for two numbers and then divides the first number
|
|
by the second. Compile the program with the following:
|
|
<P>gcc -DNDEBUG rogers_example06.c -o assert
|
|
<P>and then run ./assert and try to divide by zero. The flag -NDEBUG will
|
|
cause your assertion to generate no runtime code. This flag should
|
|
be used in all production environements
|
|
<P>Your program will core dump with almost no indication of the problem.
|
|
Now recompile the program with the following:
|
|
<P>gcc rogers_example06.c -o assert
|
|
<P>Now run the program again and again try to divide by zero. This
|
|
time it should be much more apparrent what the problem is and very easy
|
|
to locate the exact line that had the problem.
|
|
<P>As always, if you see an error in my documentation please tell me and
|
|
I will correct myself in a later document. See corrections at end
|
|
of the document to review corrections to the previous articles.
|
|
<P><B><FONT SIZE=+1>Assertions</FONT></B>
|
|
<UL><TT>#include <assert.h></TT>
|
|
<P><TT>void assert(int expression);</TT></UL>
|
|
|
|
<P>
|
|
<HR>
|
|
<P>A correction to Part *:
|
|
<BR>
|
|
<P>
|
|
<HR>
|
|
<H4>
|
|
Bibilography:</H4>
|
|
<I>The ANSI C Programming Language, Second Edition</I>, Brian W. Kernighan,
|
|
Dennis M. Ritchie, Printice Hall Software Series, 1988
|
|
<P><I>The Standard C Library</I>, P. J. Plauger, Printice Hall P T R, 1992
|
|
<P><I>The Standard C Library, Parts 1, 2, and 3</I>, Chuck Allison, <I>C/C++
|
|
Users Journal</I>, January, February, March 1995
|
|
<P>STDIO(3), BSD MANPAGE, <I>Linux Programmer's Manual</I>, 29 November
|
|
1993
|
|
|
|
<P> <HR><P>
|
|
<BR>
|
|
<CENTER>
|
|
<H4>
|
|
Previous "The Standard C Library for Linux" Articles</H4></CENTER>
|
|
<A HREF="http://www.linuxgazette.com/issue24/rogers.html"><I>The Standard
|
|
C Library for Linux, stdio.h</I>, James M. Rogers, January 1998</A>
|
|
<BR><A HREF="http://www.linuxgazette.com/issue31/rogers1.html"><I>The Standard
|
|
C Library for Linux, stdio.h</I>, James M. Rogers, July 1998</A>
|
|
<BR><A HREF="http://www.linuxgazette.com/issue32/rogers.html"><I>The Standard
|
|
C Library for Linux, stdio.h</I>, James M. Rogers, August 1998</A>
|
|
<BR><A HREF="http://www.linuxgazette.com/issue38/rogers.html"><I>The Standard
|
|
C Library for Linux, ctype.h</I>, James M. Rogers, March 1999</A>
|
|
<BR><A HREF="http://www.linuxgazette.com/issue39/rogers.html"><I>The Standard
|
|
C Library for Linux, stdlib.h</I>, James M. Rogers, April 1999</A>
|
|
|
|
|
|
<!--===================================================================-->
|
|
<P> <hr> <P>
|
|
<center><H5>Copyright © 1999, James M. Rogers <BR>
|
|
Published in Issue 41 of <i>Linux Gazette</i>, May 1999</H5></center>
|
|
|
|
<!--===================================================================-->
|
|
<P> <hr> <P>
|
|
<A HREF="./index.html"><IMG ALIGN=BOTTOM SRC="../gx/indexnew.gif"
|
|
ALT="[ TABLE OF CONTENTS ]"></A>
|
|
<A HREF="../index.html"><IMG ALIGN=BOTTOM SRC="../gx/homenew.gif"
|
|
ALT="[ FRONT PAGE ]"></A>
|
|
<A HREF="./weaver.html"><IMG SRC="../gx/back2.gif"
|
|
ALT=" Back "></A>
|
|
<A HREF="./nielsen2.html"><IMG SRC="../gx/fwd.gif" ALT=" Next "></A>
|
|
<P> <hr> <P>
|
|
<!--startcut ==========================================================-->
|
|
</BODY>
|
|
</HTML>
|
|
<!--endcut ============================================================-->
|