2264 lines
79 KiB
Text
2264 lines
79 KiB
Text
<!-- $FreeBSD: doc/en_US.ISO_8859-1/articles/programming-tools/article.sgml,v 1.11 2000/06/14 13:18:43 alex Exp $ -->
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<!-- The FreeBSD Documentation Project -->
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<!DOCTYPE ARTICLE PUBLIC "-//FreeBSD//DTD DocBook V3.1-Based Extension//EN">
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<article>
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<artheader>
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<title>A User's Guide to FreeBSD Programming Tools</title>
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<authorgroup>
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<author>
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<firstname>James</firstname>
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<surname>Raynard</surname>
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<affiliation>
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<address>
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<email>jraynard@FreeBSD.org</email>
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</address>
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</affiliation>
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</author>
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</authorgroup>
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<pubdate>August 17, 1997</pubdate>
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<copyright>
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<year>1997</year>
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<holder>James Raynard</holder>
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</copyright>
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<abstract>
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<para>This document is an introduction to using some of the
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programming tools supplied with FreeBSD, although much of it
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will be applicable to many other versions of Unix. It does
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<emphasis>not</emphasis> attempt to describe coding in any
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detail. Most of the document assumes little or no previous
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programming knowledge, although it is hoped that most
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programmers will find something of value in it</para>
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</abstract>
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</artheader>
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<sect1>
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<title>Introduction<anchor id=foo></title>
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<para>FreeBSD offers an excellent development environment.
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Compilers for C, C++, and Fortran and an assembler come with the
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basic system, not to mention a Perl interpreter and classic Unix
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tools such as <command>sed</command> and <command>awk</command>. If that is
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not enough, there are many more compilers and interpreters in
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the Ports collection. FreeBSD is very compatible with standards
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such as <acronym>POSIX</acronym> and <acronym>ANSI</acronym> C, as well with
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its own BSD heritage, so it is possible to write applications
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that will compile and run with little or no modification on a
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wide range of platforms.</para>
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<para>However, all this power can be rather overwhelming at first
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if you've never written programs on a Unix platform before.
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This document aims to help you get up and running, without
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getting too deeply into more advanced topics. The intention is
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that this document should give you enough of the basics to be
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able to make some sense of the documentation.</para>
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<para>Most of the document requires little or no knowledge of
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programming, although it does assume a basic competence with
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using Unix and a willingness to learn!</para>
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</sect1>
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<sect1>
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<title>Introduction to Programming</title>
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<para>A program is a set of instructions that tell the computer to
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do various things; sometimes the instruction it has to perform
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depends on what happened when it performed a previous
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instruction. This section gives an overview of the two main
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ways in which you can give these instructions, or
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<quote>commands</quote> as they are usually called. One way
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uses an <firstterm>interpreter</firstterm>, the other a
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<firstterm>compiler</firstterm>. As human languages are too difficult for
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a computer to understand in an unambiguous way, commands are
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usually written in one or other languages specially designed for
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the purpose.</para>
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<sect2>
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<title>Interpreters</title>
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<para>With an interpreter, the language comes as an environment,
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where you type in commands at a prompt and the environment
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executes them for you. For more complicated programs, you can
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type the commands into a file and get the interpreter to load
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the file and execute the commands in it. If anything goes
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wrong, many interpreters will drop you into a debugger to help
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you track down the problem.</para>
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<para>The advantage of this is that you can see the results of
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your commands immediately, and mistakes can be corrected
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readily. The biggest disadvantage comes when you want to
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share your programs with someone. They must have the same
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interpreter, or you must have some way of giving it to them,
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and they need to understand how to use it. Also users may not
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appreciate being thrown into a debugger if they press the
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wrong key! From a performance point of view, interpreters can
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use up a lot of memory, and generally do not generate code as
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efficiently as compilers.</para>
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<para>In my opinion, interpreted languages are the best way to
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start if you have not done any programming before. This kind
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of environment is typically found with languages like Lisp,
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Smalltalk, Perl and Basic. It could also be argued that the
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Unix shell (<command>sh</command>, <command>csh</command>) is itself an
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interpreter, and many people do in fact write shell
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<quote>scripts</quote> to help with various
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<quote>housekeeping</quote> tasks on their machine. Indeed, part
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of the original Unix philosophy was to provide lots of small
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utility programs that could be linked together in shell
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scripts to perform useful tasks.</para>
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</sect2>
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<sect2>
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<title>Interpreters available with FreeBSD</title>
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<para>Here is a list of interpreters that are available as
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<ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/">FreeBSD
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packages</ulink>, with a brief discussion of some of the
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more popular interpreted languages.</para>
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<para>To get one of these packages, all you need to do is to
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click on the hotlink for the package, then run</para>
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<screen>&prompt.root; <userinput>pkg_add <replaceable>package name</></userinput>
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</screen>
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<para>as root. Obviously, you will need to have a fully
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functional FreeBSD 2.1.0 or later system for the package to
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work!</para>
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<variablelist>
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<varlistentry>
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<term><acronym>BASIC</acronym></term>
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<listitem>
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<para>Short for Beginner's All-purpose Symbolic
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Instruction Code. Developed in the 1950s for teaching
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University students to program and provided with every
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self-respecting personal computer in the 1980s,
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<acronym>BASIC</acronym> has been the first programming
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language for many programmers. It's also the foundation
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for <trademark>Visual Basic</trademark>.</para>
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<para>The <ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/lang/bwbasic-2.10.tgz">Bywater
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Basic Interpreter</ulink> and the <ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/lang/pbasic-2.0.tgz">Phil
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Cockroft's Basic Interpreter</ulink> (formerly Rabbit
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Basic) are available as FreeBSD <ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/">FreeBSD
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packages</ulink></para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Lisp</term>
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<listitem>
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<para>A language that was developed in the late 1950s as
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an alternative to the <quote>number-crunching</quote>
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languages that were popular at the time. Instead of
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being based on numbers, Lisp is based on lists; in fact
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the name is short for <quote>List Processing</quote>.
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Very popular in AI (Artificial Intelligence)
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circles.</para>
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<para>Lisp is an extremely powerful and sophisticated
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language, but can be rather large and unwieldy.</para>
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<para>FreeBSD has <ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/gcl-2.0.tgz">GNU
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Common Lisp</ulink> available as a package.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Perl</term>
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<listitem>
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<para>Very popular with system administrators for writing
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scripts; also often used on World Wide Web servers for
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writing <acronym>CGI</acronym> scripts.</para>
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<para>The latest version (version 5) comes with FreeBSD.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Scheme</term>
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<listitem>
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<para>A dialect of Lisp that is rather more compact and
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cleaner than Common Lisp. Popular in Universities as it
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is simple enough to teach to undergraduates as a first
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language, while it has a high enough level of
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abstraction to be used in research work.</para>
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<para>FreeBSD has packages of the <ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/lang/elk-3.0.tgz">Elk
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Scheme Interpreter</ulink>, the <ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/lang/mit-scheme-7.3.tgz">MIT
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Scheme Interpreter</ulink> and the <ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/lang/scm-4e1.tgz">SCM
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Scheme Interpreter</ulink>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Icon</term>
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<listitem>
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<para><ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/lang/icon-9.0.tgz">The
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Icon Programming Language</ulink>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Logo</term>
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<listitem>
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<para><ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/lang/ucblogo-3.3.tgz">Brian
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Harvey's LOGO Interpreter</ulink>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Python</term>
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<listitem>
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<para><ulink
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URL="ftp://ftp.FreeBSD.org:pub/FreeBSD/packages/lang/python-1.2">The
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Python Object-Oriented Programming
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Language</ulink></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2>
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<title>Compilers</title>
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<para>Compilers are rather different. First of all, you write
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your code in a file (or files) using an editor. You then run
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the compiler and see if it accepts your program. If it did
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not compile, grit your teeth and go back to the editor; if it
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did compile and gave you a program, you can run it either at a
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shell command prompt or in a debugger to see if it works
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properly.
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<footnote>
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<para>If you run it in the shell, you may get a core
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dump.</para>
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</footnote></para>
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<para>Obviously, this is not quite as direct as using an
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interpreter. However it allows you to do a lot of things
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which are very difficult or even impossible with an
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interpreter, such as writing code which interacts closely with
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the operating system—or even writing your own operating
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system! It's also useful if you need to write very efficient
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code, as the compiler can take its time and optimise the code,
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which would not be acceptable in an interpreter. And
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distributing a program written for a compiler is usually more
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straightforward than one written for an interpreter—you
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can just give them a copy of the executable, assuming they
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have the same operating system as you.</para>
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<para>Compiled languages include Pascal, C and C++. C and C++
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are rather unforgiving languages, and best suited to more
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experienced programmers; Pascal, on the other hand, was
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designed as an educational language, and is quite a good
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language to start with. Unfortunately, FreeBSD doesn't have
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any Pascal support, except for a Pascal-to-C converter in the
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ports.</para>
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<para>As the edit-compile-run-debug cycle is rather tedious when
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using separate programs, many commercial compiler makers have
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produced Integrated Development Environments
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(<acronym>IDE</acronym>s for short). FreeBSD does not have an
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<acronym>IDE</acronym> as such; however it is possible to use Emacs
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for this purpose. This is discussed in <xref
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linkend="emacs">.</para>
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</sect2>
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</sect1>
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<sect1>
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<title>Compiling with <command>cc</command></title>
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<para>This section deals only with the GNU compiler for C and C++,
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since that comes with the base FreeBSD system. It can be
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invoked by either <command>cc</command> or <command>gcc</command>. The
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details of producing a program with an interpreter vary
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considerably between interpreters, and are usually well covered
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in the documentation and on-line help for the
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interpreter.</para>
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<para>Once you've written your masterpiece, the next step is to
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convert it into something that will (hopefully!) run on FreeBSD.
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This usually involves several steps, each of which is done by a
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separate program.</para>
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<procedure>
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<step>
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<para>Pre-process your source code to remove comments and do
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other tricks like expanding macros in C.</para>
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</step>
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<step>
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<para>Check the syntax of your code to see if you have obeyed
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the rules of the language. If you have not, it will
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complain!</para>
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</step>
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<step>
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<para>Convert the source code into assembly
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language—this is very close to machine code, but still
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understandable by humans. Allegedly.
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<footnote>
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<para>To be strictly accurate, <command>cc</command> converts the
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source code into its own, machine-independent
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<firstterm>p-code</firstterm> instead of assembly language at
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this stage.</para>
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</footnote></para>
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</step>
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<step>
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<para>Convert the assembly language into machine
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code—yep, we are talking bits and bytes, ones and
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zeros here.</para>
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</step>
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<step>
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<para>Check that you have used things like functions and
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global variables in a consistent way. For example, if you
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have called a non-existent function, it will
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complain.</para>
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</step>
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<step>
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<para>If you are trying to produce an executable from several
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source code files, work out how to fit them all
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together.</para>
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</step>
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<step>
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<para>Work out how to produce something that the system's
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run-time loader will be able to load into memory and
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run.</para>
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</step>
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<step>
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<para>Finally, write the executable on the file system.</para>
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</step>
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</procedure>
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<para>The word <firstterm>compiling</firstterm> is often used to refer to
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just steps 1 to 4—the others are referred to as
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<firstterm>linking</firstterm>. Sometimes step 1 is referred to as
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<firstterm>pre-processing</firstterm> and steps 3-4 as
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<firstterm>assembling</firstterm>.</para>
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<para>Fortunately, almost all this detail is hidden from you, as
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<command>cc</command> is a front end that manages calling all these
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programs with the right arguments for you; simply typing</para>
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<screen>&prompt.user; <userinput>cc foobar.c</>
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</screen>
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<para>will cause <filename>foobar.c</filename> to be compiled by all the
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steps above. If you have more than one file to compile, just do
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something like</para>
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<screen>&prompt.user; <userinput>cc foo.c bar.c</>
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</screen>
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<para>Note that the syntax checking is just that—checking
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the syntax. It will not check for any logical mistakes you may
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have made, like putting the program into an infinite loop, or
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using a bubble sort when you meant to use a binary
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sort.
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<footnote>
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<para>In case you didn't know, a binary sort is an efficient
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way of sorting things into order and a bubble sort
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isn't.</para>
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</footnote></para>
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<para>There are lots and lots of options for <command>cc</command>, which
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are all in the man page. Here are a few of the most important
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ones, with examples of how to use them.</para>
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<variablelist>
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<varlistentry>
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<term><option>-o <replaceable>filename</replaceable></option></term>
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<listitem>
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<para>The output name of the file. If you do not use this
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option, <command>cc</command> will produce an executable called
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<filename>a.out</filename>.
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<footnote>
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<para>The reasons for this are buried in the mists of
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history.</para>
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</footnote></para>
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<informalexample>
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<screen>&prompt.user; <userinput>cc foobar.c</> <lineannotation>executable is <filename>a.out</></>
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&prompt.user; <userinput>cc -o foobar foobar.c</> <lineannotation>executable is <filename>foobar</></>
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</screen>
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</informalexample>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-c</option></term>
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<listitem>
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<para>Just compile the file, do not link it. Useful for toy
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programs where you just want to check the syntax, or if
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you are using a <filename>Makefile</filename>.</para>
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<informalexample>
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<screen>&prompt.user; <userinput>cc -c foobar.c</userinput>
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</screen>
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</informalexample>
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<para>This will produce an <firstterm>object file</firstterm> (not an
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executable) called <filename>foobar.o</filename>. This
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can be linked together with other object files into an
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executable.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-g</option></term>
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<listitem>
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<para>Create a debug version of the executable. This makes
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the compiler put information into the executable about
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which line of which source file corresponds to which
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function call. A debugger can use this information to show
|
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the source code as you step through the program, which is
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<emphasis>very</emphasis> useful; the disadvantage is that
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all this extra information makes the program much bigger.
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Normally, you compile with <option>-g</option> while you
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are developing a program and then compile a <quote>release
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version</quote> without <option>-g</option> when you're
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satisfied it works properly.</para>
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<informalexample>
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|
<screen>&prompt.user; <userinput>cc -g foobar.c</userinput>
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</screen>
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</informalexample>
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<para>This will produce a debug version of the
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program.
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<footnote>
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<para>Note, we didn't use the <option>-o</option> flag
|
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to specify the executable name, so we will get an
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executable called <filename>a.out</filename>.
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Producing a debug version called
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<filename>foobar</filename> is left as an exercise for
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the reader!</para>
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</footnote></para>
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</listitem>
|
|
</varlistentry>
|
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|
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<varlistentry>
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|
<term><option>-O</option></term>
|
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|
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<listitem>
|
|
<para>Create an optimised version of the executable. The
|
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compiler performs various clever tricks to try and produce
|
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an executable that runs faster than normal. You can add a
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number after the <option>-O</option> to specify a higher
|
|
level of optimisation, but this often exposes bugs in the
|
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compiler's optimiser. For instance, the version of
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<command>cc</command> that comes with the 2.1.0 release of
|
|
FreeBSD is known to produce bad code with the
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<option>-O2</option> option in some circumstances.</para>
|
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|
|
<para>Optimisation is usually only turned on when compiling
|
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a release version.</para>
|
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<informalexample>
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|
<screen>&prompt.user; <userinput>cc -O -o foobar foobar.c</userinput>
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</screen>
|
|
</informalexample>
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|
|
<para>This will produce an optimised version of
|
|
<filename>foobar</filename>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>The following three flags will force <command>cc</command>
|
|
to check that your code complies to the relevant international
|
|
standard, often referred to as the <acronym>ANSI</acronym>
|
|
standard, though strictly speaking it is an
|
|
<acronym>ISO</acronym> standard.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><option>-Wall</option></term>
|
|
|
|
<listitem>
|
|
<para>Enable all the warnings which the authors of
|
|
<command>cc</command> believe are worthwhile. Despite the
|
|
name, it will not enable all the warnings
|
|
<command>cc</command> is capable of.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>-ansi</option></term>
|
|
|
|
<listitem>
|
|
<para>Turn off most, but not all, of the
|
|
non-<acronym>ANSI</acronym> C features provided by
|
|
<command>cc</command>. Despite the name, it does not
|
|
guarantee strictly that your code will comply to the
|
|
standard.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>-pedantic</option></term>
|
|
|
|
<listitem>
|
|
<para>Turn off <emphasis>all</emphasis>
|
|
<command>cc</command>'s non-<acronym>ANSI</acronym> C
|
|
features.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>Without these flags, <command>cc</command> will allow you to
|
|
use some of its non-standard extensions to the standard. Some
|
|
of these are very useful, but will not work with other
|
|
compilers—in fact, one of the main aims of the standard is
|
|
to allow people to write code that will work with any compiler
|
|
on any system. This is known as <firstterm>portable
|
|
code</firstterm>.</para>
|
|
|
|
<para>Generally, you should try to make your code as portable as
|
|
possible, as otherwise you may have to completely re-write the
|
|
program later to get it to work somewhere else—and who
|
|
knows what you may be using in a few years time?</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>cc -Wall -ansi -pedantic -o foobar foobar.c</userinput>
|
|
</screen>
|
|
</informalexample>
|
|
|
|
<para>This will produce an executable <filename>foobar</filename>
|
|
after checking <filename>foobar.c</filename> for standard
|
|
compliance.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><option>-l<replaceable>library</replaceable></option></term>
|
|
|
|
<listitem>
|
|
<para>Specify a function library to be used during when
|
|
linking.</para>
|
|
|
|
<para>The most common example of this is when compiling a
|
|
program that uses some of the mathematical functions in C.
|
|
Unlike most other platforms, these are in a separate
|
|
library from the standard C one and you have to tell the
|
|
compiler to add it.</para>
|
|
|
|
<para>The rule is that if the library is called
|
|
<filename>lib<replaceable>something</replaceable>.a</filename>,
|
|
you give <command>cc</command> the argument
|
|
<option>-l<replaceable>something</replaceable></option>.
|
|
For example, the math library is
|
|
<filename>libm.a</filename>, so you give
|
|
<command>cc</command> the argument <option>-lm</option>.
|
|
A common <quote>gotcha</quote> with the math library is
|
|
that it has to be the last library on the command
|
|
line.</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>cc -o foobar foobar.c -lm</userinput>
|
|
</screen>
|
|
</informalexample>
|
|
|
|
<para>This will link the math library functions into
|
|
<filename>foobar</filename>.</para>
|
|
|
|
<para>If you are compiling C++ code, you need to add
|
|
<option>-lg++</option>, or <option>-lstdc++</option> if
|
|
you are using FreeBSD 2.2 or later, to the command line
|
|
argument to link the C++ library functions.
|
|
Alternatively, you can run <command>c++</command> instead
|
|
of <command>cc</command>, which does this for you.
|
|
<command>c++</command> can also be invoked as
|
|
<command>g++</command> on FreeBSD.</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>cc -o foobar foobar.cc -lg++</userinput> <lineannotation>For FreeBSD 2.1.6 and earlier</>
|
|
&prompt.user; <userinput>cc -o foobar foobar.cc -lstdc++</userinput> <lineannotation>For FreeBSD 2.2 and later</>
|
|
&prompt.user; <userinput>c++ -o foobar foobar.cc</userinput>
|
|
</screen>
|
|
</informalexample>
|
|
|
|
<para>Each of these will both produce an executable
|
|
<filename>foobar</filename> from the C++ source file
|
|
<filename>foobar.cc</filename>. Note that, on Unix
|
|
systems, C++ source files traditionally end in
|
|
<filename>.C</filename>, <filename>.cxx</filename> or
|
|
<filename>.cc</filename>, rather than the
|
|
<trademark>MS-DOS</trademark> style
|
|
<filename>.cpp</filename> (which was already used for
|
|
something else). <command>gcc</command> used to rely on
|
|
this to work out what kind of compiler to use on the
|
|
source file; however, this restriction no longer applies,
|
|
so you may now call your C++ files
|
|
<filename>.cpp</filename> with impunity!</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<sect2>
|
|
<title>Common <command>cc</command> Queries and Problems</title>
|
|
|
|
<qandaset>
|
|
<qandaentry>
|
|
<question>
|
|
<para>I am trying to write a program which uses the
|
|
<function>sin()</function> function and I get an error
|
|
like this. What does it mean?</para>
|
|
|
|
<informalexample>
|
|
<screen>/var/tmp/cc0143941.o: Undefined symbol `_sin' referenced from text segment
|
|
</screen>
|
|
</informalexample>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>When using mathematical functions like
|
|
<function>sin()</function>, you have to tell
|
|
<command>cc</command> to link in the math library, like
|
|
so:</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>cc -o foobar foobar.c -lm</userinput>
|
|
</screen>
|
|
</informalexample>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>All right, I wrote this simple program to practice
|
|
using <option>-lm</option>. All it does is raise 2.1 to
|
|
the power of 6.</para>
|
|
|
|
<informalexample>
|
|
<programlisting>#include <stdio.h>
|
|
|
|
int main() {
|
|
float f;
|
|
|
|
f = pow(2.1, 6);
|
|
printf("2.1 ^ 6 = %f\n", f);
|
|
return 0;
|
|
}
|
|
</programlisting>
|
|
</informalexample>
|
|
|
|
<para>and I compiled it as:</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>cc temp.c -lm</userinput>
|
|
</screen>
|
|
</informalexample>
|
|
|
|
<para>like you said I should, but I get this when I run
|
|
it:</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>./a.out</userinput>
|
|
2.1 ^ 6 = 1023.000000
|
|
</screen>
|
|
</informalexample>
|
|
|
|
<para>This is <emphasis>not</emphasis> the right answer!
|
|
What is going on?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>When the compiler sees you call a function, it
|
|
checks if it has already seen a prototype for it. If it
|
|
has not, it assumes the function returns an
|
|
<type>int</type>, which is definitely not what you want
|
|
here.</para>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>So how do I fix this?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>The prototypes for the mathematical functions are in
|
|
<filename>math.h</filename>. If you include this file,
|
|
the compiler will be able to find the prototype and it
|
|
will stop doing strange things to your
|
|
calculation!</para>
|
|
|
|
<informalexample>
|
|
<programlisting>#include <math.h>
|
|
#include <stdio.h>
|
|
|
|
int main() {
|
|
...
|
|
</programlisting>
|
|
</informalexample>
|
|
|
|
<para>After recompiling it as you did before, run
|
|
it:</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>./a.out</userinput>
|
|
2.1 ^ 6 = 85.766121
|
|
</screen>
|
|
</informalexample>
|
|
|
|
<para>If you are using any of the mathematical functions,
|
|
<emphasis>always</emphasis> include
|
|
<filename>math.h</filename> and remember to link in the
|
|
math library.</para>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>I compiled a file called
|
|
<filename>foobar.c</filename> and I cannot find an
|
|
executable called <filename>foobar</filename>. Where's
|
|
it gone?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>Remember, <command>cc</command> will call the
|
|
executable <filename>a.out</filename> unless you tell it
|
|
differently. Use the
|
|
<option>-o <replaceable>filename</replaceable></option>
|
|
option:</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>cc -o foobar foobar.c</userinput>
|
|
</screen>
|
|
</informalexample>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>OK, I have an executable called
|
|
<filename>foobar</filename>, I can see it when I run
|
|
<command>ls</command>, but when I type in
|
|
<command>foobar</command> at the command prompt it tells
|
|
me there is no such file. Why can it not find
|
|
it?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>Unlike <trademark>MS-DOS</trademark>, Unix does not
|
|
look in the current directory when it is trying to find
|
|
out which executable you want it to run, unless you tell
|
|
it to. Either type <command>./foobar</command>, which
|
|
means <quote>run the file called
|
|
<filename>foobar</filename> in the current
|
|
directory</quote>, or change your <systemitem
|
|
class=environvar>PATH</systemitem> environment
|
|
variable so that it looks something like</para>
|
|
|
|
<informalexample>
|
|
<screen>bin:/usr/bin:/usr/local/bin:.
|
|
</screen>
|
|
</informalexample>
|
|
|
|
<para>The dot at the end means <quote>look in the current
|
|
directory if it is not in any of the
|
|
others</quote>.</para>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>I called my executable <filename>test</filename>,
|
|
but nothing happens when I run it. What is going
|
|
on?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>Most Unix systems have a program called
|
|
<command>test</command> in <filename>/usr/bin</filename>
|
|
and the shell is picking that one up before it gets to
|
|
checking the current directory. Either type:</para>
|
|
|
|
<informalexample>
|
|
<screen>&prompt.user; <userinput>./test</userinput>
|
|
</screen>
|
|
</informalexample>
|
|
|
|
<para>or choose a better name for your program!</para>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>I compiled my program and it seemed to run all right
|
|
at first, then there was an error and it said something
|
|
about <errorname>core dumped</errorname>. What does that
|
|
mean?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>The name <firstterm>core dump</firstterm> dates back
|
|
to the very early days of Unix, when the machines used
|
|
core memory for storing data. Basically, if the program
|
|
failed under certain conditions, the system would write
|
|
the contents of core memory to disk in a file called
|
|
<filename>core</filename>, which the programmer could
|
|
then pore over to find out what went wrong.</para>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>Fascinating stuff, but what I am supposed to do
|
|
now?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>Use <command>gdb</command> to analyse the core (see
|
|
<xref linkend="debugging">).</para>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>When my program dumped core, it said something about
|
|
a <errorname>segmentation fault</errorname>. What's
|
|
that?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>This basically means that your program tried to
|
|
perform some sort of illegal operation on memory; Unix
|
|
is designed to protect the operating system and other
|
|
programs from rogue programs.</para>
|
|
|
|
<para>Common causes for this are:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Trying to write to a <symbol>NULL</symbol>
|
|
pointer, eg</para>
|
|
|
|
<programlisting>char *foo = NULL;
|
|
strcpy(foo, "bang!");
|
|
</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Using a pointer that hasn't been initialised,
|
|
eg</para>
|
|
|
|
<programlisting>char *foo;
|
|
strcpy(foo, "bang!");
|
|
</programlisting>
|
|
|
|
<para>The pointer will have some random value that,
|
|
with luck, will point into an area of memory that
|
|
isn't available to your program and the kernel will
|
|
kill your program before it can do any damage. If
|
|
you're unlucky, it'll point somewhere inside your
|
|
own program and corrupt one of your data structures,
|
|
causing the program to fail mysteriously.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Trying to access past the end of an array,
|
|
eg</para>
|
|
|
|
<programlisting>int bar[20];
|
|
bar[27] = 6;
|
|
</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Trying to store something in read-only memory,
|
|
eg</para>
|
|
|
|
<programlisting>char *foo = "My string";
|
|
strcpy(foo, "bang!");
|
|
</programlisting>
|
|
|
|
<para>Unix compilers often put string literals like
|
|
<literal>"My string"</literal> into read-only areas
|
|
of memory.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Doing naughty things with
|
|
<function>malloc()</function> and
|
|
<function>free()</function>, eg</para>
|
|
|
|
<programlisting>char bar[80];
|
|
free(bar);
|
|
</programlisting>
|
|
|
|
<para>or</para>
|
|
|
|
<programlisting>char *foo = malloc(27);
|
|
free(foo);
|
|
free(foo);
|
|
</programlisting>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>Making one of these mistakes will not always lead to
|
|
an error, but they are always bad practice. Some
|
|
systems and compilers are more tolerant than others,
|
|
which is why programs that ran well on one system can
|
|
crash when you try them on an another.</para>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>Sometimes when I get a core dump it says
|
|
<errorname>bus error</errorname>. It says in my Unix
|
|
book that this means a hardware problem, but the
|
|
computer still seems to be working. Is this
|
|
true?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>No, fortunately not (unless of course you really do
|
|
have a hardware problem…). This is usually
|
|
another way of saying that you accessed memory in a way
|
|
you shouldn't have.</para>
|
|
</answer>
|
|
</qandaentry>
|
|
|
|
<qandaentry>
|
|
<question>
|
|
<para>This dumping core business sounds as though it could
|
|
be quite useful, if I can make it happen when I want to.
|
|
Can I do this, or do I have to wait until there's an
|
|
error?</para>
|
|
</question>
|
|
|
|
<answer>
|
|
<para>Yes, just go to another console or xterm, do</para>
|
|
|
|
<screen>&prompt.user; <userinput>ps</userinput>
|
|
</screen>
|
|
|
|
<para>to find out the process ID of your program, and
|
|
do</para>
|
|
|
|
<screen>&prompt.user; <userinput>kill -ABRT <replaceable>pid</replaceable></userinput>
|
|
</screen>
|
|
|
|
<para>where
|
|
<parameter><replaceable>pid</replaceable></parameter> is
|
|
the process ID you looked up.</para>
|
|
|
|
<para>This is useful if your program has got stuck in an
|
|
infinite loop, for instance. If your program happens to
|
|
trap <symbol>SIGABRT</symbol>, there are several other
|
|
signals which have a similar effect.</para>
|
|
</answer>
|
|
</qandaentry>
|
|
</qandaset>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>Make</title>
|
|
|
|
<sect2>
|
|
<title>What is <command>make</command>?</title>
|
|
|
|
<para>When you're working on a simple program with only one or
|
|
two source files, typing in</para>
|
|
|
|
<screen>&prompt.user; <userinput>cc file1.c file2.c</userinput>
|
|
</screen>
|
|
|
|
<para>is not too bad, but it quickly becomes very tedious when
|
|
there are several files—and it can take a while to
|
|
compile, too.</para>
|
|
|
|
<para>One way to get around this is to use object files and only
|
|
recompile the source file if the source code has changed. So
|
|
we could have something like:</para>
|
|
|
|
<screen>&prompt.user; <userinput>cc file1.o file2.o</userinput> … <userinput>file37.c</userinput> &hellip
|
|
</screen>
|
|
|
|
<para>if we'd changed <filename>file37.c</filename>, but not any
|
|
of the others, since the last time we compiled. This may
|
|
speed up the compilation quite a bit, but doesn't solve the
|
|
typing problem.</para>
|
|
|
|
<para>Or we could write a shell script to solve the typing
|
|
problem, but it would have to re-compile everything, making it
|
|
very inefficient on a large project.</para>
|
|
|
|
<para>What happens if we have hundreds of source files lying
|
|
about? What if we're working in a team with other people who
|
|
forget to tell us when they've changed one of their source
|
|
files that we use?</para>
|
|
|
|
<para>Perhaps we could put the two solutions together and write
|
|
something like a shell script that would contain some kind of
|
|
magic rule saying when a source file needs compiling. Now all
|
|
we need now is a program that can understand these rules, as
|
|
it's a bit too complicated for the shell.</para>
|
|
|
|
<para>This program is called <command>make</command>. It reads
|
|
in a file, called a <firstterm>makefile</firstterm>, that
|
|
tells it how different files depend on each other, and works
|
|
out which files need to be re-compiled and which ones don't.
|
|
For example, a rule could say something like <quote>if
|
|
<filename>fromboz.o</filename> is older than
|
|
<filename>fromboz.c</filename>, that means someone must have
|
|
changed <filename>fromboz.c</filename>, so it needs to be
|
|
re-compiled.</quote> The makefile also has rules telling
|
|
make <emphasis>how</emphasis> to re-compile the source file,
|
|
making it a much more powerful tool.</para>
|
|
|
|
<para>Makefiles are typically kept in the same directory as the
|
|
source they apply to, and can be called
|
|
<filename>makefile</filename>, <filename>Makefile</filename>
|
|
or <filename>MAKEFILE</filename>. Most programmers use the
|
|
name <filename>Makefile</filename>, as this puts it near the
|
|
top of a directory listing, where it can easily be
|
|
seen.
|
|
|
|
<footnote>
|
|
<para>They don't use the <filename>MAKEFILE</filename> form
|
|
as block capitals are often used for documentation files
|
|
like <filename>README</filename>.</para>
|
|
</footnote></para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Example of using <command>make</command></title>
|
|
|
|
<para>Here's a very simple make file:</para>
|
|
|
|
<programlisting>foo: foo.c
|
|
cc -o foo foo.c
|
|
</programlisting>
|
|
|
|
<para>It consists of two lines, a dependency line and a creation
|
|
line.</para>
|
|
|
|
<para>The dependency line here consists of the name of the
|
|
program (known as the <firstterm>target</firstterm>), followed
|
|
by a colon, then whitespace, then the name of the source file.
|
|
When <command>make</command> reads this line, it looks to see
|
|
if <filename>foo</filename> exists; if it exists, it compares
|
|
the time <filename>foo</filename> was last modified to the
|
|
time <filename>foo.c</filename> was last modified. If
|
|
<filename>foo</filename> does not exist, or is older than
|
|
<filename>foo.c</filename>, it then looks at the creation line
|
|
to find out what to do. In other words, this is the rule for
|
|
working out when <filename>foo.c</filename> needs to be
|
|
re-compiled.</para>
|
|
|
|
<para>The creation line starts with a <token>tab</token> (press
|
|
the <keycap>tab</keycap> key) and then the command you would
|
|
type to create <filename>foo</filename> if you were doing it
|
|
at a command prompt. If <filename>foo</filename> is out of
|
|
date, or does not exist, <command>make</command> then executes
|
|
this command to create it. In other words, this is the rule
|
|
which tells make how to re-compile
|
|
<filename>foo.c</filename>.</para>
|
|
|
|
<para>So, when you type <userinput>make</userinput>, it will
|
|
make sure that <filename>foo</filename> is up to date with
|
|
respect to your latest changes to <filename>foo.c</filename>.
|
|
This principle can be extended to
|
|
<filename>Makefile</filename>s with hundreds of
|
|
targets—in fact, on FreeBSD, it is possible to compile
|
|
the entire operating system just by typing <userinput>make
|
|
world</userinput> in the appropriate directory!</para>
|
|
|
|
<para>Another useful property of makefiles is that the targets
|
|
don't have to be programs. For instance, we could have a make
|
|
file that looks like this:</para>
|
|
|
|
<programlisting>foo: foo.c
|
|
cc -o foo foo.c
|
|
|
|
install:
|
|
cp foo /home/me
|
|
</programlisting>
|
|
|
|
<para>We can tell make which target we want to make by
|
|
typing:</para>
|
|
|
|
<screen>&prompt.user; <userinput>make <replaceable>target</replaceable></userinput>
|
|
</screen>
|
|
|
|
<para><command>make</command> will then only look at that target
|
|
and ignore any others. For example, if we type
|
|
<userinput>make foo</userinput> with the makefile above, make
|
|
will ignore the <action>install</action> target.</para>
|
|
|
|
<para>If we just type <userinput>make</userinput> on its own,
|
|
make will always look at the first target and then stop
|
|
without looking at any others. So if we typed
|
|
<userinput>make</userinput> here, it will just go to the
|
|
<action>foo</action> target, re-compile
|
|
<filename>foo</filename> if necessary, and then stop without
|
|
going on to the <action>install</action> target.</para>
|
|
|
|
<para>Notice that the <action>install</action> target doesn't
|
|
actually depend on anything! This means that the command on
|
|
the following line is always executed when we try to make that
|
|
target by typing <userinput>make install</userinput>. In this
|
|
case, it will copy <filename>foo</filename> into the user's
|
|
home directory. This is often used by application makefiles,
|
|
so that the application can be installed in the correct
|
|
directory when it has been correctly compiled.</para>
|
|
|
|
<para>This is a slightly confusing subject to try and explain.
|
|
If you don't quite understand how <command>make</command>
|
|
works, the best thing to do is to write a simple program like
|
|
<quote>hello world</quote> and a make file like the one above
|
|
and experiment. Then progress to using more than one source
|
|
file, or having the source file include a header file. The
|
|
<command>touch</command> command is very useful here—it
|
|
changes the date on a file without you having to edit
|
|
it.</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>FreeBSD Makefiles</title>
|
|
|
|
<para>Makefiles can be rather complicated to write. Fortunately,
|
|
BSD-based systems like FreeBSD come with some very powerful
|
|
ones as part of the system. One very good example of this is
|
|
the FreeBSD ports system. Here's the essential part of a
|
|
typical ports <filename>Makefile</filename>:</para>
|
|
|
|
<programlisting>MASTER_SITES= ftp://freefall.cdrom.com/pub/FreeBSD/LOCAL_PORTS/
|
|
DISTFILES= scheme-microcode+dist-7.3-freebsd.tgz
|
|
|
|
.include <bsd.port.mk>
|
|
</programlisting>
|
|
|
|
<para>Now, if we go to the directory for this port and type
|
|
<userinput>make</userinput>, the following happens:</para>
|
|
|
|
<procedure>
|
|
<step>
|
|
<para>A check is made to see if the source code for this
|
|
port is already on the system.</para>
|
|
</step>
|
|
|
|
<step>
|
|
<para>If it isn't, an FTP connection to the URL in
|
|
<symbol>MASTER_SITES</symbol> is set up to download the
|
|
source.</para>
|
|
</step>
|
|
|
|
<step>
|
|
<para>The checksum for the source is calculated and compared
|
|
it with one for a known, good, copy of the source. This
|
|
is to make sure that the source was not corrupted while in
|
|
transit.</para>
|
|
</step>
|
|
|
|
<step>
|
|
<para>Any changes required to make the source work on
|
|
FreeBSD are applied—this is known as
|
|
<firstterm>patching</firstterm>.</para>
|
|
</step>
|
|
|
|
<step>
|
|
<para>Any special configuration needed for the source is
|
|
done. (Many Unix program distributions try to work out
|
|
which version of Unix they are being compiled on and which
|
|
optional Unix features are present—this is where
|
|
they are given the information in the FreeBSD ports
|
|
scenario).</para>
|
|
</step>
|
|
|
|
<step>
|
|
<para>The source code for the program is compiled. In
|
|
effect, we change to the directory where the source was
|
|
unpacked and do <command>make</command>—the
|
|
program's own make file has the necessary information to
|
|
build the program.</para>
|
|
</step>
|
|
|
|
<step>
|
|
<para>We now have a compiled version of the program. If we
|
|
wish, we can test it now; when we feel confident about the
|
|
program, we can type <userinput>make install</userinput>.
|
|
This will cause the program and any supporting files it
|
|
needs to be copied into the correct location; an entry is
|
|
also made into a <database>package database</database>, so
|
|
that the port can easily be uninstalled later if we change
|
|
our mind about it.</para>
|
|
</step>
|
|
</procedure>
|
|
|
|
<para>Now I think you'll agree that's rather impressive for a
|
|
four line script!</para>
|
|
|
|
<para>The secret lies in the last line, which tells
|
|
<command>make</command> to look in the system makefile called
|
|
<filename>bsd.port.mk</filename>. It's easy to overlook this
|
|
line, but this is where all the clever stuff comes
|
|
from—someone has written a makefile that tells
|
|
<command>make</command> to do all the things above (plus a
|
|
couple of other things I didn't mention, including handling
|
|
any errors that may occur) and anyone can get access to that
|
|
just by putting a single line in their own make file!</para>
|
|
|
|
<para>If you want to have a look at these system makefiles,
|
|
they're in <filename>/usr/share/mk</filename>, but it's
|
|
probably best to wait until you've had a bit of practice with
|
|
makefiles, as they are very complicated (and if you do look at
|
|
them, make sure you have a flask of strong coffee
|
|
handy!)</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>More advanced uses of <command>make</command></title>
|
|
|
|
<para><command>Make</command> is a very powerful tool, and can
|
|
do much more than the simple example above shows.
|
|
Unfortunately, there are several different versions of
|
|
<command>make</command>, and they all differ considerably.
|
|
The best way to learn what they can do is probably to read the
|
|
documentation—hopefully this introduction will have
|
|
given you a base from which you can do this.</para>
|
|
|
|
<para>The version of make that comes with FreeBSD is the
|
|
<application>Berkeley make</application>; there is a tutorial
|
|
for it in <filename>/usr/share/doc/psd/12.make</filename>. To
|
|
view it, do</para>
|
|
|
|
<screen>&prompt.user; <userinput>zmore paper.ascii.gz</userinput>
|
|
</screen>
|
|
|
|
<para>in that directory.</para>
|
|
|
|
<para>Many applications in the ports use <application>GNU
|
|
make</application>, which has a very good set of
|
|
<quote>info</quote> pages. If you have installed any of these
|
|
ports, <application>GNU make</application> will automatically
|
|
have been installed as <command>gmake</command>. It's also
|
|
available as a port and package in its own right.</para>
|
|
|
|
<para>To view the info pages for <application>GNU
|
|
make</application>, you will have to edit the
|
|
<filename>dir</filename> file in the
|
|
<filename>/usr/local/info</filename> directory to add an entry
|
|
for it. This involves adding a line like</para>
|
|
|
|
<programlisting> * Make: (make). The GNU Make utility.
|
|
</programlisting>
|
|
|
|
<para>to the file. Once you have done this, you can type
|
|
<userinput>info</userinput> and then select
|
|
<guimenuitem>make</guimenuitem> from the menu (or in
|
|
<application>Emacs</application>, do <userinput>C-h
|
|
i</userinput>).</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="debugging">
|
|
<title>Debugging</title>
|
|
|
|
<sect2>
|
|
<title>The Debugger</title>
|
|
|
|
<para>The debugger that comes with FreeBSD is called
|
|
<command>gdb</command> (<application>GNU
|
|
debugger</application>). You start it up by typing</para>
|
|
|
|
<screen>&prompt.user; <userinput>gdb <replaceable>progname</replaceable></userinput>
|
|
</screen>
|
|
|
|
<para>although most people prefer to run it inside
|
|
<application>Emacs</application>. You can do this by:</para>
|
|
|
|
<screen><userinput>M-x gdb RET <replaceable>progname</replaceable> RET</userinput>
|
|
</screen>
|
|
|
|
<para>Using a debugger allows you to run the program under more
|
|
controlled circumstances. Typically, you can step through the
|
|
program a line at a time, inspect the value of variables,
|
|
change them, tell the debugger to run up to a certain point
|
|
and then stop, and so on. You can even attach to a program
|
|
that's already running, or load a core file to investigate why
|
|
the program crashed. It's even possible to debug the kernel,
|
|
though that's a little trickier than the user applications
|
|
we'll be discussing in this section.</para>
|
|
|
|
<para><command>gdb</command> has quite good on-line help, as
|
|
well as a set of info pages, so this section will concentrate
|
|
on a few of the basic commands.</para>
|
|
|
|
<para>Finally, if you find its text-based command-prompt style
|
|
off-putting, there's a graphical front-end for it <ulink
|
|
URL="../../ports/devel.html">xxgdb</ulink> in the ports
|
|
collection.</para>
|
|
|
|
<para>This section is intended to be an introduction to using
|
|
<command>gdb</command> and does not cover specialised topics
|
|
such as debugging the kernel.</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Running a program in the debugger</title>
|
|
|
|
<para>You'll need to have compiled the program with the
|
|
<option>-g</option> option to get the most out of using
|
|
<command>gdb</command>. It will work without, but you'll only
|
|
see the name of the function you're in, instead of the source
|
|
code. If you see a line like:</para>
|
|
|
|
<screen>… (no debugging symbols found) …
|
|
</screen>
|
|
|
|
<para>when <command>gdb</command> starts up, you'll know that
|
|
the program wasn't compiled with the <option>-g</option>
|
|
option.</para>
|
|
|
|
<para>At the <command>gdb</command> prompt, type
|
|
<userinput>break main</userinput>. This will tell the
|
|
debugger to skip over the preliminary set-up code in the
|
|
program and start at the beginning of your code. Now type
|
|
<userinput>run</userinput> to start the program—it will
|
|
start at the beginning of the set-up code and then get stopped
|
|
by the debugger when it calls <function>main()</function>.
|
|
(If you've ever wondered where <function>main()</function>
|
|
gets called from, now you know!).</para>
|
|
|
|
<para>You can now step through the program, a line at a time, by
|
|
pressing <command>n</command>. If you get to a function call,
|
|
you can step into it by pressing <command>s</command>. Once
|
|
you're in a function call, you can return from stepping into a
|
|
function call by pressing <command>f</command>. You can also
|
|
use <command>up</command> and <command>down</command> to take
|
|
a quick look at the caller.</para>
|
|
|
|
<para>Here's a simple example of how to spot a mistake in a
|
|
program with <command>gdb</command>. This is our program
|
|
(with a deliberate mistake):</para>
|
|
|
|
<programlisting>#include <stdio.h>
|
|
|
|
int bazz(int anint);
|
|
|
|
main() {
|
|
int i;
|
|
|
|
printf("This is my program\n");
|
|
bazz(i);
|
|
return 0;
|
|
}
|
|
|
|
int bazz(int anint) {
|
|
printf("You gave me %d\n", anint);
|
|
return anint;
|
|
}
|
|
</programlisting>
|
|
|
|
<para>This program sets <symbol>i</symbol> to be
|
|
<literal>5</literal> and passes it to a function
|
|
<function>bazz()</function> which prints out the number we
|
|
gave it.</para>
|
|
|
|
<para>When we compile and run the program we get</para>
|
|
|
|
<screen>&prompt.user; <userinput>cc -g -o temp temp.c</userinput>
|
|
&prompt.user; <userinput>./temp</userinput>
|
|
This is my program
|
|
anint = 4231
|
|
</screen>
|
|
|
|
<para>That wasn't what we expected! Time to see what's going
|
|
on!</para>
|
|
|
|
<screen>&prompt.user; <userinput>gdb temp</userinput>
|
|
GDB is free software and you are welcome to distribute copies of it
|
|
under certain conditions; type "show copying" to see the conditions.
|
|
There is absolutely no warranty for GDB; type "show warranty" for details.
|
|
GDB 4.13 (i386-unknown-freebsd), Copyright 1994 Free Software Foundation, Inc.
|
|
(gdb) <userinput>break main</> <lineannotation>Skip the set-up code</>
|
|
Breakpoint 1 at 0x160f: file temp.c, line 9. <lineannotation><command>gdb</command> puts breakpoint at <function>main()</></>
|
|
(gdb) <userinput>run</> <lineannotation>Run as far as <function>main()</></>
|
|
Starting program: /home/james/tmp/temp <lineannotation>Program starts running</>
|
|
|
|
Breakpoint 1, main () at temp.c:9 <lineannotation><command>gdb</command> stops at <function>main()</></>
|
|
(gdb) <userinput>n</> <lineannotation>Go to next line</>
|
|
This is my program <lineannotation>Program prints out</>
|
|
(gdb) <userinput>s</> <lineannotation>step into <function>bazz()</></>
|
|
bazz (anint=4231) at temp.c:17 <lineannotation><command>gdb</command> displays stack frame</>
|
|
(gdb)
|
|
</screen>
|
|
|
|
<para>Hang on a minute! How did <symbol>anint</symbol> get to be
|
|
<literal>4231</literal>? Didn't we set it to be
|
|
<literal>5</literal> in <function>main()</function>? Let's
|
|
move up to <function>main()</function> and have a look.</para>
|
|
|
|
<screen>(gdb) <userinput>up</> <lineannotation>Move up call stack</>
|
|
#1 0x1625 in main () at temp.c:11 <lineannotation><command>gdb</command> displays stack frame</>
|
|
(gdb) <userinput>p i</> <lineannotation>Show us the value of <symbol>i</></>
|
|
$1 = 4231 <lineannotation><command>gdb</command> displays <literal>4231</></>
|
|
</screen>
|
|
|
|
<para>Oh dear! Looking at the code, we forgot to initialise
|
|
<symbol>i</symbol>. We meant to put</para>
|
|
|
|
<programlisting><lineannotation>…</>
|
|
main() {
|
|
int i;
|
|
|
|
i = 5;
|
|
printf("This is my program\n");
|
|
<lineannotation>&hellip</>
|
|
</programlisting>
|
|
|
|
<para>but we left the <literal>i=5;</literal> line out. As we
|
|
didn't initialise <symbol>i</symbol>, it had whatever number
|
|
happened to be in that area of memory when the program ran,
|
|
which in this case happened to be
|
|
<literal>4231</literal>.</para>
|
|
|
|
<note>
|
|
<para><command>gdb</command> displays the stack frame every
|
|
time we go into or out of a function, even if we're using
|
|
<command>up</command> and <command>down</command> to move
|
|
around the call stack. This shows the name of the function
|
|
and the values of its arguments, which helps us keep track
|
|
of where we are and what's going on. (The stack is a
|
|
storage area where the program stores information about the
|
|
arguments passed to functions and where to go when it
|
|
returns from a function call).</para>
|
|
</note>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Examining a core file</title>
|
|
|
|
<para>A core file is basically a file which contains the
|
|
complete state of the process when it crashed. In <quote>the
|
|
good old days</quote>, programmers had to print out hex
|
|
listings of core files and sweat over machine code manuals,
|
|
but now life is a bit easier. Incidentally, under FreeBSD and
|
|
other 4.4BSD systems, a core file is called
|
|
<filename><replaceable>progname</replaceable>.core</filename> instead of just
|
|
<filename>core</filename>, to make it clearer which program a
|
|
core file belongs to.</para>
|
|
|
|
<para>To examine a core file, start up <command>gdb</command> in
|
|
the usual way. Instead of typing <command>break</command> or
|
|
<command>run</command>, type</para>
|
|
|
|
<screen>(gdb) <userinput>core <replaceable>progname</replaceable>.core</userinput>
|
|
</screen>
|
|
|
|
<para>If you're not in the same directory as the core file,
|
|
you'll have to do <userinput>dir
|
|
/path/to/core/file</userinput> first.</para>
|
|
|
|
<para>You should see something like this:</para>
|
|
|
|
<screen>&prompt.user; <userinput>gdb a.out</userinput>
|
|
GDB is free software and you are welcome to distribute copies of it
|
|
under certain conditions; type "show copying" to see the conditions.
|
|
There is absolutely no warranty for GDB; type "show warranty" for details.
|
|
GDB 4.13 (i386-unknown-freebsd), Copyright 1994 Free Software Foundation, Inc.
|
|
(gdb) <userinput>core a.out.core</userinput>
|
|
Core was generated by `a.out'.
|
|
Program terminated with signal 11, Segmentation fault.
|
|
Cannot access memory at address 0x7020796d.
|
|
#0 0x164a in bazz (anint=0x5) at temp.c:17
|
|
(gdb)
|
|
</screen>
|
|
|
|
<para>In this case, the program was called
|
|
<filename>a.out</filename>, so the core file is called
|
|
<filename>a.out.core</filename>. We can see that the program
|
|
crashed due to trying to access an area in memory that was not
|
|
available to it in a function called
|
|
<function>bazz</function>.</para>
|
|
|
|
<para>Sometimes it's useful to be able to see how a function was
|
|
called, as the problem could have occurred a long way up the
|
|
call stack in a complex program. The <command>bt</command>
|
|
command causes <command>gdb</command> to print out a
|
|
back-trace of the call stack:</para>
|
|
|
|
<screen>(gdb) <userinput>bt</userinput>
|
|
#0 0x164a in bazz (anint=0x5) at temp.c:17
|
|
#1 0xefbfd888 in end ()
|
|
#2 0x162c in main () at temp.c:11
|
|
(gdb)
|
|
</screen>
|
|
|
|
<para>The <function>end()</function> function is called when a
|
|
program crashes; in this case, the <function>bazz()</function>
|
|
function was called from <function>main()</function>.</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Attaching to a running program</title>
|
|
|
|
<para>One of the neatest features about <command>gdb</command>
|
|
is that it can attach to a program that's already running. Of
|
|
course, that assumes you have sufficient permissions to do so.
|
|
A common problem is when you are stepping through a program
|
|
that forks, and you want to trace the child, but the debugger
|
|
will only let you trace the parent.</para>
|
|
|
|
<para>What you do is start up another <command>gdb</command>,
|
|
use <command>ps</command> to find the process ID for the
|
|
child, and do</para>
|
|
|
|
<screen>(gdb) <userinput>attach <replaceable>pid</replaceable></userinput>
|
|
</screen>
|
|
|
|
<para>in <command>gdb</command>, and then debug as usual.</para>
|
|
|
|
<para><quote>That's all very well,</quote> you're probably
|
|
thinking, <quote>but by the time I've done that, the child
|
|
process will be over the hill and far away</quote>. Fear
|
|
not, gentle reader, here's how to do it (courtesy of the
|
|
<command>gdb</command> info pages):</para>
|
|
|
|
<screen><lineannotation>&hellip</lineannotation>
|
|
if ((pid = fork()) < 0) /* _Always_ check this */
|
|
error();
|
|
else if (pid == 0) { /* child */
|
|
int PauseMode = 1;
|
|
|
|
while (PauseMode)
|
|
sleep(10); /* Wait until someone attaches to us */
|
|
<lineannotation>&hellip</lineannotation>
|
|
} else { /* parent */
|
|
<lineannotation>&hellip</lineannotation>
|
|
</screen>
|
|
|
|
<para>Now all you have to do is attach to the child, set
|
|
<symbol>PauseMode</symbol> to <literal>0</literal>, and wait
|
|
for the <function>sleep()</function> call to return!</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="emacs">
|
|
<title>Using Emacs as a Development Environment</title>
|
|
|
|
<sect2>
|
|
<title>Emacs</title>
|
|
|
|
<para>Unfortunately, Unix systems don't come with the kind of
|
|
everything-you-ever-wanted-and-lots-more-you-didn't-in-one-gigantic-package
|
|
integrated development environments that other systems
|
|
have.
|
|
|
|
<footnote>
|
|
<para>At least, not unless you pay out very large sums of
|
|
money.</para>
|
|
</footnote>
|
|
|
|
However, it is possible to set up your own environment. It
|
|
may not be as pretty, and it may not be quite as integrated,
|
|
but you can set it up the way you want it. And it's free.
|
|
And you have the source to it.</para>
|
|
|
|
<para>The key to it all is Emacs. Now there are some people who
|
|
loathe it, but many who love it. If you're one of the former,
|
|
I'm afraid this section will hold little of interest to you.
|
|
Also, you'll need a fair amount of memory to run it—I'd
|
|
recommend 8MB in text mode and 16MB in X as the bare minimum
|
|
to get reasonable performance.</para>
|
|
|
|
<para>Emacs is basically a highly customisable
|
|
editor—indeed, it has been customised to the point where
|
|
it's more like an operating system than an editor! Many
|
|
developers and sysadmins do in fact spend practically all
|
|
their time working inside Emacs, leaving it only to log
|
|
out.</para>
|
|
|
|
<para>It's impossible even to summarise everything Emacs can do
|
|
here, but here are some of the features of interest to
|
|
developers:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Very powerful editor, allowing search-and-replace on
|
|
both strings and regular expressions (patterns), jumping
|
|
to start/end of block expression, etc, etc.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Pull-down menus and online help.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Language-dependent syntax highlighting and
|
|
indentation.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Completely customisable.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>You can compile and debug programs within
|
|
Emacs.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>On a compilation error, you can jump to the offending
|
|
line of source code.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Friendly-ish front-end to the <command>info</command>
|
|
program used for reading GNU hypertext documentation,
|
|
including the documentation on Emacs itself.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Friendly front-end to <command>gdb</command>, allowing
|
|
you to look at the source code as you step through your
|
|
program.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>You can read Usenet news and mail while your program
|
|
is compiling.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>And doubtless many more that I've overlooked.</para>
|
|
|
|
<para>Emacs can be installed on FreeBSD using <ulink
|
|
URL="../../ports/editors.html">the Emacs
|
|
port</ulink>.</para>
|
|
|
|
<para>Once it's installed, start it up and do <userinput>C-h
|
|
t</userinput> to read an Emacs tutorial—that means
|
|
hold down the <keycap>control</keycap> key, press
|
|
<keycap>h</keycap>, let go of the <keycap>control</keycap>
|
|
key, and then press <keycap>t</keycap>. (Alternatively, you
|
|
can you use the mouse to select <guimenuitem>Emacs
|
|
Tutorial</guimenuitem> from the <guimenu>Help</guimenu>
|
|
menu).</para>
|
|
|
|
<para>Although Emacs does have menus, it's well worth learning
|
|
the key bindings, as it's much quicker when you're editing
|
|
something to press a couple of keys than to try and find the
|
|
mouse and then click on the right place. And, when you're
|
|
talking to seasoned Emacs users, you'll find they often
|
|
casually throw around expressions like <quote><literal>M-x
|
|
replace-s RET foo RET bar RET</literal></quote> so it's
|
|
useful to know what they mean. And in any case, Emacs has far
|
|
too many useful functions for them to all fit on the menu
|
|
bars.</para>
|
|
|
|
<para>Fortunately, it's quite easy to pick up the key-bindings,
|
|
as they're displayed next to the menu item. My advice is to
|
|
use the menu item for, say, opening a file until you
|
|
understand how it works and feel confident with it, then try
|
|
doing C-x C-f. When you're happy with that, move on to
|
|
another menu command.</para>
|
|
|
|
<para>If you can't remember what a particular combination of
|
|
keys does, select <guimenuitem>Describe Key</guimenuitem> from
|
|
the <guimenu>Help</guimenu> menu and type it in—Emacs
|
|
will tell you what it does. You can also use the
|
|
<guimenuitem>Command Apropos</guimenuitem> menu item to find
|
|
out all the commands which contain a particular word in them,
|
|
with the key binding next to it.</para>
|
|
|
|
<para>By the way, the expression above means hold down the
|
|
<keysym>Meta</keysym> key, press <keysym>x</keysym>, release
|
|
the <keysym>Meta</keysym> key, type
|
|
<userinput>replace-s</userinput> (short for
|
|
<literal>replace-string</literal>—another feature of
|
|
Emacs is that you can abbreviate commands), press the
|
|
<keysym>return</keysym> key, type <userinput>foo</userinput>
|
|
(the string you want replaced), press the
|
|
<keysym>return</keysym> key, type bar (the string you want to
|
|
replace <literal>foo</literal> with) and press
|
|
<keysym>return</keysym> again. Emacs will then do the
|
|
search-and-replace operation you've just requested.</para>
|
|
|
|
<para>If you're wondering what on earth the
|
|
<keysym>Meta</keysym> key is, it's a special key that many
|
|
Unix workstations have. Unfortunately, PC's don't have one,
|
|
so it's usually the <keycap>alt</keycap> key (or if you're
|
|
unlucky, the <keysym>escape</keysym> key).</para>
|
|
|
|
<para>Oh, and to get out of Emacs, do <command>C-x C-c</command>
|
|
(that means hold down the <keysym>control</keysym> key, press
|
|
<keysym>x</keysym>, press <keysym>c</keysym> and release the
|
|
<keysym>control</keysym> key). If you have any unsaved files
|
|
open, Emacs will ask you if you want to save them. (Ignore
|
|
the bit in the documentation where it says
|
|
<command>C-z</command> is the usual way to leave
|
|
Emacs—that leaves Emacs hanging around in the
|
|
background, and is only really useful if you're on a system
|
|
which doesn't have virtual terminals).</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Configuring Emacs</title>
|
|
|
|
<para>Emacs does many wonderful things; some of them are built
|
|
in, some of them need to be configured.</para>
|
|
|
|
<para>Instead of using a proprietary macro language for
|
|
configuration, Emacs uses a version of Lisp specially adapted
|
|
for editors, known as Emacs Lisp. This can be quite useful if
|
|
you want to go on and learn something like Common Lisp, as
|
|
it's considerably smaller than Common Lisp (although still
|
|
quite big!).</para>
|
|
|
|
<para>The best way to learn Emacs Lisp is to download the <ulink
|
|
URL="ftp://prep.ai.mit.edu:pub/gnu/elisp-manual-19-2.4.tar.gz">Emacs
|
|
Tutorial</ulink></para>
|
|
|
|
<para>However, there's no need to actually know any Lisp to get
|
|
started with configuring Emacs, as I've included a sample
|
|
<filename>.emacs</filename> file, which should be enough to
|
|
get you started. Just copy it into your home directory and
|
|
restart Emacs if it's already running; it will read the
|
|
commands from the file and (hopefully) give you a useful basic
|
|
setup.</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>A sample <filename>.emacs</filename> file</title>
|
|
|
|
<para>Unfortunately, there's far too much here to explain it in
|
|
detail; however there are one or two points worth
|
|
mentioning.</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Everything beginning with a <literal>;</literal> is a comment
|
|
and is ignored by Emacs.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>In the first line, the
|
|
<literal>-*- Emacs-Lisp -*-</literal> is so that
|
|
we can edit the <filename>.emacs</filename> file itself
|
|
within Emacs and get all the fancy features for editing
|
|
Emacs Lisp. Emacs usually tries to guess this based on
|
|
the filename, and may not get it right for
|
|
<filename>.emacs</filename>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The <keysym>tab</keysym> key is bound to an
|
|
indentation function in some modes, so when you press the
|
|
tab key, it will indent the current line of code. If you
|
|
want to put a <token>tab</token> character in whatever
|
|
you're writing, hold the <keysym>control</keysym> key down
|
|
while you're pressing the <keysym>tab</keysym> key.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>This file supports syntax highlighting for C, C++,
|
|
Perl, Lisp and Scheme, by guessing the language from the
|
|
filename.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Emacs already has a pre-defined function called
|
|
<function>next-error</function>. In a compilation output
|
|
window, this allows you to move from one compilation error
|
|
to the next by doing <command>M-n</command>; we define a
|
|
complementary function,
|
|
<function>previous-error</function>, that allows you to go
|
|
to a previous error by doing <command>M-p</command>. The
|
|
nicest feature of all is that <command>C-c C-c</command>
|
|
will open up the source file in which the error occurred
|
|
and jump to the appropriate line.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>We enable Emacs's ability to act as a server, so that
|
|
if you're doing something outside Emacs and you want to
|
|
edit a file, you can just type in</para>
|
|
|
|
<screen>&prompt.user; <userinput>emacsclient <replaceable>filename</replaceable></userinput>
|
|
</screen>
|
|
|
|
<para>and then you can edit the file in your
|
|
Emacs!
|
|
|
|
<footnote>
|
|
<para>Many Emacs users set their <systemitem
|
|
class=environvar>EDITOR</systemitem> environment to
|
|
<literal>emacsclient</literal> so this happens every
|
|
time they need to edit a file.</para>
|
|
</footnote></para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<example>
|
|
<title>A sample <filename>.emacs</filename> file</title>
|
|
|
|
<programlisting>;; -*-Emacs-Lisp-*-
|
|
|
|
;; This file is designed to be re-evaled; use the variable first-time
|
|
;; to avoid any problems with this.
|
|
(defvar first-time t
|
|
"Flag signifying this is the first time that .emacs has been evaled")
|
|
|
|
;; Meta
|
|
(global-set-key "\M- " 'set-mark-command)
|
|
(global-set-key "\M-\C-h" 'backward-kill-word)
|
|
(global-set-key "\M-\C-r" 'query-replace)
|
|
(global-set-key "\M-r" 'replace-string)
|
|
(global-set-key "\M-g" 'goto-line)
|
|
(global-set-key "\M-h" 'help-command)
|
|
|
|
;; Function keys
|
|
(global-set-key [f1] 'manual-entry)
|
|
(global-set-key [f2] 'info)
|
|
(global-set-key [f3] 'repeat-complex-command)
|
|
(global-set-key [f4] 'advertised-undo)
|
|
(global-set-key [f5] 'eval-current-buffer)
|
|
(global-set-key [f6] 'buffer-menu)
|
|
(global-set-key [f7] 'other-window)
|
|
(global-set-key [f8] 'find-file)
|
|
(global-set-key [f9] 'save-buffer)
|
|
(global-set-key [f10] 'next-error)
|
|
(global-set-key [f11] 'compile)
|
|
(global-set-key [f12] 'grep)
|
|
(global-set-key [C-f1] 'compile)
|
|
(global-set-key [C-f2] 'grep)
|
|
(global-set-key [C-f3] 'next-error)
|
|
(global-set-key [C-f4] 'previous-error)
|
|
(global-set-key [C-f5] 'display-faces)
|
|
(global-set-key [C-f8] 'dired)
|
|
(global-set-key [C-f10] 'kill-compilation)
|
|
|
|
;; Keypad bindings
|
|
(global-set-key [up] "\C-p")
|
|
(global-set-key [down] "\C-n")
|
|
(global-set-key [left] "\C-b")
|
|
(global-set-key [right] "\C-f")
|
|
(global-set-key [home] "\C-a")
|
|
(global-set-key [end] "\C-e")
|
|
(global-set-key [prior] "\M-v")
|
|
(global-set-key [next] "\C-v")
|
|
(global-set-key [C-up] "\M-\C-b")
|
|
(global-set-key [C-down] "\M-\C-f")
|
|
(global-set-key [C-left] "\M-b")
|
|
(global-set-key [C-right] "\M-f")
|
|
(global-set-key [C-home] "\M-<")
|
|
(global-set-key [C-end] "\M->")
|
|
(global-set-key [C-prior] "\M-<")
|
|
(global-set-key [C-next] "\M->")
|
|
|
|
;; Mouse
|
|
(global-set-key [mouse-3] 'imenu)
|
|
|
|
;; Misc
|
|
(global-set-key [C-tab] "\C-q\t") ; Control tab quotes a tab.
|
|
(setq backup-by-copying-when-mismatch t)
|
|
|
|
;; Treat 'y' or <CR> as yes, 'n' as no.
|
|
(fset 'yes-or-no-p 'y-or-n-p)
|
|
(define-key query-replace-map [return] 'act)
|
|
(define-key query-replace-map [?\C-m] 'act)
|
|
|
|
;; Load packages
|
|
(require 'desktop)
|
|
(require 'tar-mode)
|
|
|
|
;; Pretty diff mode
|
|
(autoload 'ediff-buffers "ediff" "Intelligent Emacs interface to diff" t)
|
|
(autoload 'ediff-files "ediff" "Intelligent Emacs interface to diff" t)
|
|
(autoload 'ediff-files-remote "ediff"
|
|
"Intelligent Emacs interface to diff")
|
|
|
|
(if first-time
|
|
(setq auto-mode-alist
|
|
(append '(("\\.cpp$" . c++-mode)
|
|
("\\.hpp$" . c++-mode)
|
|
("\\.lsp$" . lisp-mode)
|
|
("\\.scm$" . scheme-mode)
|
|
("\\.pl$" . perl-mode)
|
|
) auto-mode-alist)))
|
|
|
|
;; Auto font lock mode
|
|
(defvar font-lock-auto-mode-list
|
|
(list 'c-mode 'c++-mode 'c++-c-mode 'emacs-lisp-mode 'lisp-mode 'perl-mode 'scheme-mode)
|
|
"List of modes to always start in font-lock-mode")
|
|
|
|
(defvar font-lock-mode-keyword-alist
|
|
'((c++-c-mode . c-font-lock-keywords)
|
|
(perl-mode . perl-font-lock-keywords))
|
|
"Associations between modes and keywords")
|
|
|
|
(defun font-lock-auto-mode-select ()
|
|
"Automatically select font-lock-mode if the current major mode is
|
|
in font-lock-auto-mode-list"
|
|
(if (memq major-mode font-lock-auto-mode-list)
|
|
(progn
|
|
(font-lock-mode t))
|
|
)
|
|
)
|
|
|
|
(global-set-key [M-f1] 'font-lock-fontify-buffer)
|
|
|
|
;; New dabbrev stuff
|
|
;(require 'new-dabbrev)
|
|
(setq dabbrev-always-check-other-buffers t)
|
|
(setq dabbrev-abbrev-char-regexp "\\sw\\|\\s_")
|
|
(add-hook 'emacs-lisp-mode-hook
|
|
'(lambda ()
|
|
(set (make-local-variable 'dabbrev-case-fold-search) nil)
|
|
(set (make-local-variable 'dabbrev-case-replace) nil)))
|
|
(add-hook 'c-mode-hook
|
|
'(lambda ()
|
|
(set (make-local-variable 'dabbrev-case-fold-search) nil)
|
|
(set (make-local-variable 'dabbrev-case-replace) nil)))
|
|
(add-hook 'text-mode-hook
|
|
'(lambda ()
|
|
(set (make-local-variable 'dabbrev-case-fold-search) t)
|
|
(set (make-local-variable 'dabbrev-case-replace) t)))
|
|
|
|
;; C++ and C mode...
|
|
(defun my-c++-mode-hook ()
|
|
(setq tab-width 4)
|
|
(define-key c++-mode-map "\C-m" 'reindent-then-newline-and-indent)
|
|
(define-key c++-mode-map "\C-ce" 'c-comment-edit)
|
|
(setq c++-auto-hungry-initial-state 'none)
|
|
(setq c++-delete-function 'backward-delete-char)
|
|
(setq c++-tab-always-indent t)
|
|
(setq c-indent-level 4)
|
|
(setq c-continued-statement-offset 4)
|
|
(setq c++-empty-arglist-indent 4))
|
|
|
|
(defun my-c-mode-hook ()
|
|
(setq tab-width 4)
|
|
(define-key c-mode-map "\C-m" 'reindent-then-newline-and-indent)
|
|
(define-key c-mode-map "\C-ce" 'c-comment-edit)
|
|
(setq c-auto-hungry-initial-state 'none)
|
|
(setq c-delete-function 'backward-delete-char)
|
|
(setq c-tab-always-indent t)
|
|
;; BSD-ish indentation style
|
|
(setq c-indent-level 4)
|
|
(setq c-continued-statement-offset 4)
|
|
(setq c-brace-offset -4)
|
|
(setq c-argdecl-indent 0)
|
|
(setq c-label-offset -4))
|
|
|
|
;; Perl mode
|
|
(defun my-perl-mode-hook ()
|
|
(setq tab-width 4)
|
|
(define-key c++-mode-map "\C-m" 'reindent-then-newline-and-indent)
|
|
(setq perl-indent-level 4)
|
|
(setq perl-continued-statement-offset 4))
|
|
|
|
;; Scheme mode...
|
|
(defun my-scheme-mode-hook ()
|
|
(define-key scheme-mode-map "\C-m" 'reindent-then-newline-and-indent))
|
|
|
|
;; Emacs-Lisp mode...
|
|
(defun my-lisp-mode-hook ()
|
|
(define-key lisp-mode-map "\C-m" 'reindent-then-newline-and-indent)
|
|
(define-key lisp-mode-map "\C-i" 'lisp-indent-line)
|
|
(define-key lisp-mode-map "\C-j" 'eval-print-last-sexp))
|
|
|
|
;; Add all of the hooks...
|
|
(add-hook 'c++-mode-hook 'my-c++-mode-hook)
|
|
(add-hook 'c-mode-hook 'my-c-mode-hook)
|
|
(add-hook 'scheme-mode-hook 'my-scheme-mode-hook)
|
|
(add-hook 'emacs-lisp-mode-hook 'my-lisp-mode-hook)
|
|
(add-hook 'lisp-mode-hook 'my-lisp-mode-hook)
|
|
(add-hook 'perl-mode-hook 'my-perl-mode-hook)
|
|
|
|
;; Complement to next-error
|
|
(defun previous-error (n)
|
|
"Visit previous compilation error message and corresponding source code."
|
|
(interactive "p")
|
|
(next-error (- n)))
|
|
|
|
;; Misc...
|
|
(transient-mark-mode 1)
|
|
(setq mark-even-if-inactive t)
|
|
(setq visible-bell nil)
|
|
(setq next-line-add-newlines nil)
|
|
(setq compile-command "make")
|
|
(setq suggest-key-bindings nil)
|
|
(put 'eval-expression 'disabled nil)
|
|
(put 'narrow-to-region 'disabled nil)
|
|
(put 'set-goal-column 'disabled nil)
|
|
|
|
;; Elisp archive searching
|
|
(autoload 'format-lisp-code-directory "lispdir" nil t)
|
|
(autoload 'lisp-dir-apropos "lispdir" nil t)
|
|
(autoload 'lisp-dir-retrieve "lispdir" nil t)
|
|
(autoload 'lisp-dir-verify "lispdir" nil t)
|
|
|
|
;; Font lock mode
|
|
(defun my-make-face (face colour &optional bold)
|
|
"Create a face from a colour and optionally make it bold"
|
|
(make-face face)
|
|
(copy-face 'default face)
|
|
(set-face-foreground face colour)
|
|
(if bold (make-face-bold face))
|
|
)
|
|
|
|
(if (eq window-system 'x)
|
|
(progn
|
|
(my-make-face 'blue "blue")
|
|
(my-make-face 'red "red")
|
|
(my-make-face 'green "dark green")
|
|
(setq font-lock-comment-face 'blue)
|
|
(setq font-lock-string-face 'bold)
|
|
(setq font-lock-type-face 'bold)
|
|
(setq font-lock-keyword-face 'bold)
|
|
(setq font-lock-function-name-face 'red)
|
|
(setq font-lock-doc-string-face 'green)
|
|
(add-hook 'find-file-hooks 'font-lock-auto-mode-select)
|
|
|
|
(setq baud-rate 1000000)
|
|
(global-set-key "\C-cmm" 'menu-bar-mode)
|
|
(global-set-key "\C-cms" 'scroll-bar-mode)
|
|
(global-set-key [backspace] 'backward-delete-char)
|
|
; (global-set-key [delete] 'delete-char)
|
|
(standard-display-european t)
|
|
(load-library "iso-transl")))
|
|
|
|
;; X11 or PC using direct screen writes
|
|
(if window-system
|
|
(progn
|
|
;; (global-set-key [M-f1] 'hilit-repaint-command)
|
|
;; (global-set-key [M-f2] [?\C-u M-f1])
|
|
(setq hilit-mode-enable-list
|
|
'(not text-mode c-mode c++-mode emacs-lisp-mode lisp-mode
|
|
scheme-mode)
|
|
hilit-auto-highlight nil
|
|
hilit-auto-rehighlight 'visible
|
|
hilit-inhibit-hooks nil
|
|
hilit-inhibit-rebinding t)
|
|
(require 'hilit19)
|
|
(require 'paren))
|
|
(setq baud-rate 2400) ; For slow serial connections
|
|
)
|
|
|
|
;; TTY type terminal
|
|
(if (and (not window-system)
|
|
(not (equal system-type 'ms-dos)))
|
|
(progn
|
|
(if first-time
|
|
(progn
|
|
(keyboard-translate ?\C-h ?\C-?)
|
|
(keyboard-translate ?\C-? ?\C-h)))))
|
|
|
|
;; Under UNIX
|
|
(if (not (equal system-type 'ms-dos))
|
|
(progn
|
|
(if first-time
|
|
(server-start))))
|
|
|
|
;; Add any face changes here
|
|
(add-hook 'term-setup-hook 'my-term-setup-hook)
|
|
(defun my-term-setup-hook ()
|
|
(if (eq window-system 'pc)
|
|
(progn
|
|
;; (set-face-background 'default "red")
|
|
)))
|
|
|
|
;; Restore the "desktop" - do this as late as possible
|
|
(if first-time
|
|
(progn
|
|
(desktop-load-default)
|
|
(desktop-read)))
|
|
|
|
;; Indicate that this file has been read at least once
|
|
(setq first-time nil)
|
|
|
|
;; No need to debug anything now
|
|
(setq debug-on-error nil)
|
|
|
|
;; All done
|
|
(message "All done, %s%s" (user-login-name) ".")
|
|
</programlisting>
|
|
</example>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Extending the Range of Languages Emacs Understands</title>
|
|
|
|
<para>Now, this is all very well if you only want to program in
|
|
the languages already catered for in the
|
|
<filename>.emacs</filename> file (C, C++, Perl, Lisp and
|
|
Scheme), but what happens if a new language called
|
|
<quote>whizbang</quote> comes out, full of exciting
|
|
features?</para>
|
|
|
|
<para>The first thing to do is find out if whizbang comes with
|
|
any files that tell Emacs about the language. These usually
|
|
end in <filename>.el</filename>, short for <quote>Emacs
|
|
Lisp</quote>. For example, if whizbang is a FreeBSD port, we
|
|
can locate these files by doing</para>
|
|
|
|
<screen>&prompt.user; <userinput>find /usr/ports/lang/whizbang -name "*.el" -print</userinput>
|
|
</screen>
|
|
|
|
<para>and install them by copying them into the Emacs site Lisp
|
|
directory. On FreeBSD 2.1.0-RELEASE, this is
|
|
<filename>/usr/local/share/emacs/site-lisp</filename>.</para>
|
|
|
|
<para>So for example, if the output from the find command
|
|
was</para>
|
|
|
|
<screen>/usr/ports/lang/whizbang/work/misc/whizbang.el
|
|
</screen>
|
|
|
|
<para>we would do</para>
|
|
|
|
<screen>&prompt.root; <userinput>cp /usr/ports/lang/whizbang/work/misc/whizbang.el /usr/local/share/emacs/site-lisp</userinput>
|
|
</screen>
|
|
|
|
<para>Next, we need to decide what extension whizbang source
|
|
files have. Let's say for the sake of argument that they all
|
|
end in <filename>.wiz</filename>. We need to add an entry to
|
|
our <filename>.emacs</filename> file to make sure Emacs will
|
|
be able to use the information in
|
|
<filename>whizbang.el</filename>.</para>
|
|
|
|
<para>Find the <symbol>auto-mode-alist entry</symbol> in
|
|
<filename>.emacs</filename> and add a line for whizbang, such
|
|
as:</para>
|
|
|
|
<programlisting><lineannotation>…</>
|
|
("\\.lsp$" . lisp-mode)
|
|
("\\.wiz$" . whizbang-mode)
|
|
("\\.scm$" . scheme-mode)
|
|
<lineannotation>…</>
|
|
</programlisting>
|
|
|
|
<para>This means that Emacs will automatically go into
|
|
<function>whizbang-mode</function> when you edit a file ending
|
|
in <filename>.wiz</filename>.</para>
|
|
|
|
<para>Just below this, you'll find the
|
|
<symbol>font-lock-auto-mode-list</symbol> entry. Add
|
|
<function>whizbang-mode</function> to it like so:</para>
|
|
|
|
<programlisting>;; Auto font lock mode
|
|
(defvar font-lock-auto-mode-list
|
|
(list 'c-mode 'c++-mode 'c++-c-mode 'emacs-lisp-mode 'whizbang-mode 'lisp-mode 'perl-mode 'scheme-mode)
|
|
"List of modes to always start in font-lock-mode")
|
|
</programlisting>
|
|
|
|
<para>This means that Emacs will always enable
|
|
<function>font-lock-mode</function> (ie syntax highlighting)
|
|
when editing a <filename>.wiz</filename> file.</para>
|
|
|
|
<para>And that's all that's needed. If there's anything else
|
|
you want done automatically when you open up a
|
|
<filename>.wiz</filename> file, you can add a
|
|
<function>whizbang-mode hook</function> (see
|
|
<function>my-scheme-mode-hook</function> for a simple example
|
|
that adds <function>auto-indent</function>).</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>Further Reading</title>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Brian Harvey and Matthew Wright
|
|
<emphasis>Simply Scheme</emphasis>
|
|
MIT 1994.<!-- <br> -->
|
|
ISBN 0-262-08226-8</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Randall Schwartz
|
|
<emphasis>Learning Perl</emphasis>
|
|
O'Reilly 1993<!-- <br> -->
|
|
ISBN 1-56592-042-2</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Patrick Henry Winston and Berthold Klaus Paul Horn
|
|
<emphasis>Lisp (3rd Edition)</emphasis>
|
|
Addison-Wesley 1989<!-- <br> -->
|
|
ISBN 0-201-08319-1</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Brian W. Kernighan and Rob Pike
|
|
<emphasis>The Unix Programming Environment</emphasis>
|
|
Prentice-Hall 1984<!-- <br> -->
|
|
ISBN 0-13-937681-X</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Brian W. Kernighan and Dennis M. Ritchie
|
|
<emphasis>The C Programming Language (2nd Edition)</emphasis>
|
|
Prentice-Hall 1988<!-- <br> -->
|
|
ISBN 0-13-110362-8</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Bjarne Stroustrup
|
|
<emphasis>The C++ Programming Language</emphasis>
|
|
Addison-Wesley 1991<!-- <br> -->
|
|
ISBN 0-201-53992-6</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>W. Richard Stevens
|
|
<emphasis>Advanced Programming in the Unix Environment</emphasis>
|
|
Addison-Wesley 1992<!-- <br> -->
|
|
ISBN 0-201-56317-7</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>W. Richard Stevens
|
|
<emphasis>Unix Network Programming</emphasis>
|
|
Prentice-Hall 1990<!-- <br> -->
|
|
ISBN 0-13-949876-1</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</sect1>
|
|
</article>
|