1835 lines
72 KiB
Text
1835 lines
72 KiB
Text
<!-- $Id: article.sgml,v 1.5 1999-03-21 16:16:17 wosch Exp $ -->
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<!-- The FreeBSD Documentation Project -->
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<!DOCTYPE BOOK PUBLIC "-//Davenport//DTD DocBook V3.0//EN">
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<book>
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<bookinfo>
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<bookbiblio>
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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></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><para>This document is an introduction to using some of the programming
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tools supplied with FreeBSD, although much of it will be applicable to
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many other versions of Unix. It does <emphasis>not</emphasis> attempt to describe
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coding in any detail. Most of the document assumes little or no
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previous programming knowledge, although it is hoped that most
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programmers will find something of value in it</para></abstract>
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</bookbiblio>
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</bookinfo>
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<chapter>
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<title>Introduction<anchor id=foo></title>
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<para>FreeBSD offers an excellent development environment. Compilers
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for C, C++, and Fortran and an assembler come with the basic system,
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not to mention a Perl interpreter and classic Unix tools such as
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<command>sed</> and <command>awk</>. If that is not enough, there are
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many more compilers and interpreters in the Ports collection. FreeBSD
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is very compatible with standards such as <acronym>POSIX</> and
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<acronym>ANSI</> C, as well with its own BSD heritage, so it is
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possible to write applications that will compile and run with little
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or no modification on a wide range of platforms.</para>
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<para>However, all this power can be rather overwhelming at first if
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you've never written programs on a Unix platform before. This
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document aims to help you get up and running, without getting too
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deeply into more advanced topics. The intention is that this document
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should give you enough of the basics to be able to make some sense of
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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 using
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Unix and a willingness to learn!</para>
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</chapter>
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<chapter>
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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 do
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various things; sometimes the instruction it has to perform depends
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on what happened when it performed a previous instruction. This
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section gives an overview of the two main ways in which you can give
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these instructions, or <quote>commands</quote> as they are usually
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called. One way uses an <firstterm>interpreter</>, the other a
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<firstterm>compiler</>. As human languages are too difficult for a
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computer to understand in an unambiguous way, commands are usually
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written in one or other languages specially designed for the
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purpose.</para>
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<sect1>
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<title>Interpreters</title>
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<para>With an interpreter, the language comes as an environment, where you
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type in commands at a prompt and the environment executes them for
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you. For more complicated programs, you can type the commands into a
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file and get the interpreter to load the file and execute the commands
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in it. If anything goes wrong, many interpreters will drop you into a
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debugger to help you track down the problem.</para>
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<para>The advantage of this is that you can see the results of your
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commands immediately, and mistakes can be corrected readily. The
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biggest disadvantage comes when you want to share your programs with
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someone. They must have the same interpreter, or you must have some
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way of giving it to them, and they need to understand how to use it.
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Also users may not appreciate being thrown into a debugger if they
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press the wrong key! From a performance point of view, interpreters
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can 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 start
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if you have not done any programming before. This kind of environment
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is typically found with languages like Lisp, Smalltalk, Perl and
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Basic. It could also be argued that the Unix shell (<command>sh</>,
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<command>csh</>) is itself an interpreter, and many people do in fact
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write shell <quote>scripts</quote> to help with various
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<quote>housekeeping</> tasks on their machine. Indeed, part of the
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original Unix philosophy was to provide lots of small utility
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programs that could be linked together in shell scripts to perform
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useful tasks.</para>
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</sect1>
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<sect1>
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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 <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 more popular
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interpreted languages. </para>
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<para>To get one of these packages, all you need to do is to click on
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the hotlink for the package, then run
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<screen>$ <userinput>pkg_add <replaceable>package name</></userinput></screen>
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</para>
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<para>as root. Obviously, you will need to have a fully functional FreeBSD
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2.1.0 or later system for the package to work!</para>
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<para>
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<variablelist>
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<varlistentry><term><acronym>BASIC</></term>
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<listitem><para>Short for Beginner's All-purpose Symbolic Instruction
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Code. Developed in the 1950s for teaching University students to
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program and provided with every self-respecting personal computer in
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the 1980s, <acronym>BASIC</> has been the first programming language
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for many programmers. It's also the foundation for <trademark>Visual
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Basic</>.</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 Basic) are
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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><term>Lisp</term>
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<listitem><para>A language that was developed in the late 1950s as an alternative to
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the <quote>number-crunching</quote> languages that were popular at the time.
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Instead of being based on numbers, Lisp is based on lists; in fact
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the name is short for <quote>List Processing</quote>. Very popular in AI
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(Artificial Intelligence) circles.</para>
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<para>Lisp is an extremely powerful and sophisticated language, but
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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><term>Perl</term>
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<listitem><para>Very popular with system administrators for writing
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scripts; also often used on World Wide Web servers for writing <acronym>CGI</>
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scripts.</para>
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<para>Version 4, which is probably still the most widely-used
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version, comes with FreeBSD; the newer <ulink
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URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/perl-5.001.tgz">Perl
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Version 5</ulink> is available as a package.</para>
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</listitem>
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</varlistentry>
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<varlistentry><term>Scheme</term>
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<listitem><para>A dialect of Lisp that is rather more compact and
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cleaner than Common Lisp. Popular in Universities as it is simple
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enough to teach to undergraduates as a first language, while it has a
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high enough level of abstraction to be used in research work.</para>
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<para>FreeBSD has packages of the
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<ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/elk-3.0.tgz">Elk Scheme Interpreter</ulink>, the
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<ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/mit-scheme-7.3.tgz">MIT Scheme Interpreter</ulink> and the
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<ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/scm-4e1.tgz">SCM Scheme Interpreter</ulink>.</para>
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</listitem>
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</varlistentry>
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<varlistentry><term>Icon</term>
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<listitem><para><ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/icon-9.0.tgz">The Icon Programming Language</ulink>.</para>
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</listitem>
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</varlistentry>
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<varlistentry><term>Logo</term>
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<listitem><para><ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/ucblogo-3.3.tgz">Brian Harvey's LOGO Interpreter</ulink>.</para>
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</listitem>
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</varlistentry>
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<varlistentry><term>Python</term>
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<listitem><para><ulink URL="ftp://ftp.freebsd.org:pub/FreeBSD/packages/lang/python-1.2">The Python Object-Oriented Programming Language</ulink></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</sect1>
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<sect1>
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<title>Compilers</title>
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<para>Compilers are rather different. First of all, you write your
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code in a file (or files) using an editor. You then run the compiler
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and see if it accepts your program. If it did not compile, grit your
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teeth and go back to the editor; if it did compile and gave you a
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program, you can run it either at a shell command prompt or in a
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debugger to see if it works properly.<footnote><para>If you run it in
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the shell, you may get a core dump.</para></footnote></para>
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<para>Obviously, this is not quite as direct as using an interpreter.
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However it allows you to do a lot of things which are very difficult
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or even impossible with an interpreter, such as writing code which
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interacts closely with the operating system—or even writing
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your own operating system! It's also useful if you need to write very
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efficient code, as the compiler can take its time and optimise the
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code, 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 can just
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give them a copy of the executable, assuming they have the same
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operating system as you.</para>
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<para>Compiled languages include Pascal, C and C++. C and C++ are rather
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unforgiving languages, and best suited to more experienced
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programmers; Pascal, on the other hand, was designed as an educational
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language, and is quite a good language to start with. Unfortunately,
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FreeBSD doesn't have any Pascal support, except for a Pascal-to-C
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converter in the 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 (<acronym>IDE</acronym>s
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for short). FreeBSD does not have an <acronym>IDE</> as such; however
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it is possible to use Emacs for this purpose. This is discussed in
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<xref linkend="emacs">.</para>
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</sect1>
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</chapter>
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<chapter>
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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 invoked by
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either <command>cc</> or <command>gcc</>. The details of producing a
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program with an interpreter vary considerably between interpreters,
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and are usually well covered in the documentation and on-line help
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for the interpreter.</para>
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<para>Once you've written your masterpiece, the next step is to convert it
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into something that will (hopefully!) run on FreeBSD. This usually
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involves several steps, each of which is done by a separate
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program.</para>
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<procedure>
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<step><para>Pre-process your source code to remove comments and do other
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tricks like expanding macros in C.
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</para></step>
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<step><para>Check the syntax of your code to see if you have obeyed the
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rules of the language. If you have not, it will complain!
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</para></step>
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<step><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.<footnote><para>To be strictly
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accurate, <command>cc</> converts the source code into its own,
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machine-independent <firstterm>p-code</> instead of assembly language
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at this stage.</para></footnote></para></step>
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<step><para>Convert the assembly language into machine
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code—yep, we are talking bits and bytes, ones and zeros
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here.</para></step>
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<step><para>Check that you have used things like functions and global
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variables in a consistent way. For example, if you have called a
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non-existent function, it will complain.</para></step>
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<step><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 together.</para></step>
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<step><para>Work out how to produce something that the system's run-time
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loader will be able to load into memory and run.</para></step>
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<step><para>Finally, write the executable on the file
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system.</para></step>
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</procedure>
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<para>The word <firstterm>compiling</> is often used to refer to just
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steps 1 to 4—the others are referred to as
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<firstterm>linking</>. Sometimes step 1 is referred to as
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<firstterm>pre-processing</> and steps 3-4 as
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<firstterm>assembling</>.</para>
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<para>Fortunately, almost all this detail is hidden from you, as
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<command>cc</> is a front end that manages calling all these programs
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with the right arguments for you; simply typing
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<screen>$ <userinput>cc foobar.c</></screen></para>
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<para>will cause <filename>foobar.c</> 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
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<screen>$ <userinput>cc foo.c bar.c</></screen>
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</para>
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<para>Note that the syntax checking is just that—checking the
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syntax. It will not check for any logical mistakes you may have made,
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like putting the program into an infinite loop, or using a bubble
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sort when you meant to use a binary sort.<footnote><para>In case you
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didn't know, a binary sort is an efficient way of sorting things into
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order and a bubble sort isn't.</para></footnote></para>
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<para>There are lots and lots of options for <command>cc</>, which
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are all in the man page. Here are a few of the most important ones,
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with examples of how to use them.</para>
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<variablelist>
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<varlistentry><term><option>-o <replaceable>filename</replaceable></></term>
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<listitem><para>The output name of the file. If you do not use this
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option, <command>cc</> will produce an executable called
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<filename>a.out</>.<footnote><para>The reasons for this are buried in
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the mists of history.</para></footnote></para>
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<informalexample>
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<screen>$ <userinput>cc foobar.c</> <lineannotation>executable is <filename>a.out</></>
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$ <userinput>cc -o foobar foobar.c</> <lineannotation>executable is <filename>foobar</></></screen>
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</informalexample>
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</listitem>
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</varlistentry>
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<varlistentry><term><option>-c</option></term>
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<listitem><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 you are using
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a <filename>Makefile</filename>.</para>
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<informalexample>
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<screen>$ <userinput>cc -c foobar.c</userinput></screen>
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</informalexample>
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<para>This will produce an <firstterm>object file</> (not an
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executable) called <filename>foobar.o</filename>. This can be linked
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together with other object files into an executable.</para>
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</listitem>
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</varlistentry>
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<varlistentry><term><option>-g</option></term>
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<listitem><para>Create a debug version of the executable. This makes
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the compiler put information into the executable about which line of
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which source file corresponds to which function call. A debugger can
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use this information to show the source code as you step through the
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program, which is <emphasis>very</emphasis> useful; the disadvantage
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is that all this extra information makes the program much bigger.
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Normally, you compile with <option>-g</option> while you are
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developing a program and then compile a <quote>release
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version</quote> without <option>-g</option> when you're satisfied it
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works properly.</para>
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<informalexample>
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<screen>$ <userinput>cc -g foobar.c</userinput></screen>
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</informalexample>
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<para>This will produce a debug version of the
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program.<footnote><para>Note, we didn't use the <option>-o</option>
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flag to specify the executable name, so we will get an executable
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called <filename>a.out</filename>. Producing a debug version called
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<filename>foobar</filename> is left as an exercise for the
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reader!</para></footnote></para>
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</listitem>
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</varlistentry>
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<varlistentry><term><option>-O</option></term>
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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 an
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executable that runs faster than normal. You can add a number after
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the <option>-O</option> to specify a higher level of optimisation,
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but this often exposes bugs in the compiler's optimiser. For
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instance, the version of <command>cc</command> that comes with the
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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 a release
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version.</para>
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<informalexample>
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<screen>$ <userinput>cc -O -o foobar foobar.c</userinput></screen>
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</informalexample>
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<para>This will produce an optimised version of
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<filename>foobar</filename>.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>The following three flags will force <command>cc</command> to
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check that your code complies to the relevant international standard,
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|
often referred to as the <acronym>ANSI</acronym> standard, though
|
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strictly speaking it is an <acronym>ISO</acronym> standard.</para>
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<variablelist>
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<varlistentry><term><option>-Wall</option></term>
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<listitem><para>Enable all the warnings which the authors of
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<command>cc</command> believe are worthwhile. Despite the name, it
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will not enable all the warnings <command>cc</command> is capable
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of.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>-ansi</option></term>
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<listitem>
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<para>Turn off most, but not all, of the non-<acronym>ANSI</> C
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features provided by <command>cc</command>. Despite the name, it does
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not guarantee strictly that your code will comply to the
|
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standard.</para>
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</listitem>
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</varlistentry>
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<varlistentry><term><option>-pedantic</option></term>
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<listitem>
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|
<para>Turn off <emphasis>all</emphasis>
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<command>cc</command>'s non-<acronym>ANSI</> C features.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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|
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<para>Without these flags, <command>cc</command> will allow you to
|
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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>$ <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>$ <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>$ <userinput>cc -o foobar foobar.cc -lg++</userinput> <lineannotation>For FreeBSD 2.1.6 and earlier</>
|
|
$ <userinput>cc -o foobar foobar.cc -lstdc++</userinput> <lineannotation>For FreeBSD 2.2 and later</>
|
|
$ <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>
|
|
|
|
<sect1>
|
|
<title>Common <command>cc</command> Queries and Problems</title>
|
|
|
|
<para>Q. 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?
|
|
<informalexample>
|
|
<screen>/var/tmp/cc0143941.o: Undefined symbol `_sin' referenced from text segment</screen>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<para>A. When using mathematical functions like
|
|
<function>sin()</function>, you have to tell <command>cc</command> to
|
|
link in the math library, like so:
|
|
<informalexample>
|
|
<screen>$ <userinput>cc -o foobar foobar.c -lm</userinput></screen>
|
|
</informalexample></para>
|
|
|
|
<para>Q. 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.
|
|
<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>
|
|
and I compiled it as:
|
|
<informalexample>
|
|
<screen>$ <userinput>cc temp.c -lm</userinput></screen>
|
|
</informalexample>
|
|
like you said I should, but I get this when I run it:
|
|
<informalexample>
|
|
<screen>$ <userinput>./a.out</userinput>
|
|
2.1 ^ 6 = 1023.000000</screen>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<para>This is <emphasis>not</emphasis> the right answer! What is
|
|
going on?</para>
|
|
|
|
<para>A. 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>
|
|
|
|
<para>Q. So how do I fix this?</para>
|
|
|
|
<para>A. 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!
|
|
<informalexample>
|
|
<programlisting>#include <math.h>
|
|
#include <stdio.h>
|
|
|
|
int main() {
|
|
...</programlisting>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<para>After recompiling it as you did before, run it:
|
|
<informalexample>
|
|
<screen>$ <userinput>./a.out</userinput>
|
|
2.1 ^ 6 = 85.766121</screen>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<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>
|
|
|
|
<para>Q. I compiled a file called <filename>foobar.c</filename> and I
|
|
cannot find an executable called <filename>foobar</filename>. Where's
|
|
it gone?</para>
|
|
|
|
<para>A. 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:
|
|
<informalexample>
|
|
<screen>$ <userinput>cc -o foobar foobar.c</userinput></screen>
|
|
</informalexample>
|
|
</para>
|
|
|
|
<para>Q. 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>
|
|
|
|
<para>A. 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
|
|
<informalexample>
|
|
<screen>bin:/usr/bin:/usr/local/bin:.</screen>
|
|
</informalexample>
|
|
The dot at the end means <quote>look in the current directory if it is not in
|
|
any of the others</quote>.</para>
|
|
|
|
<para>Q. I called my executable <filename>test</filename>, but
|
|
nothing happens when I run it. What is going on?</para>
|
|
|
|
<para>A. 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:
|
|
<informalexample>
|
|
<screen>$ <userinput>./test</userinput></screen>
|
|
</informalexample>
|
|
or choose a better name for your program!</para>
|
|
|
|
<para>Q. 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>
|
|
|
|
<para>A. 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>
|
|
|
|
<para>Q. Fascinating stuff, but what I am supposed to do now?</para>
|
|
|
|
<para>A. Use <command>gdb</command> to analyse the core (see <xref
|
|
linkend="debugging">).</para>
|
|
|
|
<para>Q. When my program dumped core, it said something about a
|
|
<errorname>segmentation fault</errorname>. What's that?</para>
|
|
|
|
<para>A. 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:
|
|
<itemizedlist>
|
|
<listitem><para>Trying to write to a <symbol>NULL</symbol> pointer, eg
|
|
<programlisting>char *foo = NULL;
|
|
strcpy(foo, "bang!");</programlisting>
|
|
</para></listitem>
|
|
|
|
<listitem><para>Using a pointer that hasn't been initialised, eg
|
|
<programlisting>char *foo;
|
|
strcpy(foo, "bang!");</programlisting>
|
|
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
|
|
<programlisting>int bar[20];
|
|
bar[27] = 6;</programlisting></para></listitem>
|
|
|
|
<listitem><para> Trying to store something in read-only memory, eg
|
|
<programlisting>char *foo = "My string";
|
|
strcpy(foo, "bang!");</programlisting>
|
|
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
|
|
<programlisting>char bar[80];
|
|
free(bar);</programlisting>
|
|
or
|
|
<programlisting>char *foo = malloc(27);
|
|
free(foo);
|
|
free(foo);</programlisting>
|
|
</para></listitem>
|
|
|
|
</itemizedlist></para>
|
|
|
|
<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>
|
|
|
|
<para>Q. 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>
|
|
|
|
<para>A. 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>
|
|
|
|
<para>Q. 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>
|
|
|
|
<para>A. Yes, just go to another console or xterm, do
|
|
<screen>$ <userinput>ps</userinput></screen>
|
|
to find out the process ID of your program, and do
|
|
<screen>$ <userinput>kill -ABRT <replaceable>pid</replaceable></userinput></screen>
|
|
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>
|
|
|
|
</sect1>
|
|
</chapter>
|
|
|
|
|
|
<chapter>
|
|
<title>Make</title>
|
|
|
|
<sect1>
|
|
<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
|
|
<screen>$ <userinput>cc file1.c file2.c</userinput></screen>
|
|
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:
|
|
<screen>$ <userinput>cc file1.o file2.o</userinput> … <userinput>file37.c</userinput> &hellip</screen>
|
|
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>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<title>Example of using <command>make</command></title>
|
|
|
|
<para>Here's a very simple make file:
|
|
<programlisting>foo: foo.c
|
|
cc -o foo foo.c</programlisting>
|
|
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:
|
|
<programlisting>foo: foo.c
|
|
cc -o foo foo.c
|
|
|
|
install:
|
|
cp foo /home/me</programlisting></para>
|
|
|
|
<para>We can tell make which target we want to make by typing:
|
|
<screen>$ <userinput>make <replaceable>target</replaceable></userinput></screen>
|
|
<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>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<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>:
|
|
<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>
|
|
|
|
<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>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<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
|
|
<screen>$ <userinput>zmore paper.ascii.gz</userinput></screen>
|
|
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
|
|
<programlisting> * Make: (make). The GNU Make utility.</programlisting>
|
|
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>
|
|
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="debugging">
|
|
<title>Debugging</title>
|
|
|
|
<sect1>
|
|
<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
|
|
<screen>$ <userinput>gdb <replaceable>progname</replaceable></userinput></screen>
|
|
although most people prefer to run it inside
|
|
<application>Emacs</application>. You can do this by:
|
|
<screen><userinput>M-x gdb RET <replaceable>progname</replaceable> RET</userinput></screen></para>
|
|
|
|
<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>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<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:
|
|
<screen>… (no debugging symbols found) …</screen>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):
|
|
<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>
|
|
|
|
<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
|
|
<screen>$ <userinput>cc -g -o temp temp.c</userinput>
|
|
$ <userinput>./temp</userinput>
|
|
This is my program
|
|
anint = 4231</screen></para>
|
|
|
|
<para>That wasn't what we expected! Time to see what's going
|
|
on!<screen>$ <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>
|
|
|
|
|
|
<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>
|
|
|
|
<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>
|
|
Oh dear! Looking at the code, we forgot to initialise
|
|
<symbol>i</symbol>. We meant to put
|
|
<programlisting><lineannotation>…</>
|
|
main() {
|
|
int i;
|
|
|
|
i = 5;
|
|
printf("This is my program\n");
|
|
<lineannotation>&hellip</></programlisting>
|
|
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>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<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</>.core</> 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
|
|
<screen>(gdb) <userinput>core <replaceable>progname</replaceable>.core</userinput></screen>
|
|
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:
|
|
<screen>$ <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>
|
|
|
|
<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:
|
|
<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>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>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<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<screen>(gdb) <userinput>attach <replaceable>pid</replaceable></userinput></screen>
|
|
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):
|
|
<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>
|
|
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>
|
|
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="emacs">
|
|
<title>Using Emacs as a Development Environment</title>
|
|
|
|
<sect1>
|
|
<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:
|
|
<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>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>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<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>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<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>
|
|
|
|
<para>
|
|
<itemizedlist>
|
|
|
|
<listitem><para>Everything beginning with a <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
|
|
<screen>$ <userinput>emacsclient <replaceable>filename</replaceable></userinput></screen>
|
|
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>
|
|
</para>
|
|
|
|
<example>
|
|
<title>A sample <filename>.emacs</filename> file</title>
|
|
<screen>;; -*-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") </screen>
|
|
|
|
<screen>(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)))</screen>
|
|
|
|
<screen>;; 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) ".")
|
|
</screen>
|
|
</example>
|
|
|
|
</sect1>
|
|
|
|
<sect1>
|
|
<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
|
|
<screen>$ <userinput>find /usr/ports/lang/whizbang -name "*.el" -print</userinput></screen>
|
|
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
|
|
<screen>/usr/ports/lang/whizbang/work/misc/whizbang.el</screen>
|
|
we would do
|
|
<screen>$ <userinput>cp /usr/ports/lang/whizbang/work/misc/whizbang.el /usr/local/share/emacs/site-lisp</userinput></screen>
|
|
</para>
|
|
|
|
<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:
|
|
<programlisting><lineannotation>…</>
|
|
("\\.lsp$" . lisp-mode)
|
|
("\\.wiz$" . whizbang-mode)
|
|
("\\.scm$" . scheme-mode)
|
|
<lineannotation>…</></programlisting>
|
|
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:
|
|
<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>
|
|
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>
|
|
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter>
|
|
<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>
|
|
|
|
</chapter>
|
|
</book>
|