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diff --git a/www/code.html b/www/code.html index 45822b1f..ad2a7a8b 100644 --- a/www/code.html +++ b/www/code.html @@ -1,5 +1,40 @@ <!--#include file="header.html" --> +<h1>Simplicity first: spending your complexity budget wisely.</h1> + +<p>The primary goal of toybox is _simple_ code. Keeping the code small is +second, with speed and lots of features coming in somewhere after that.</p> + +<p>These goals are usually complementary: simplifying code generally reduces +its size (both in terms of binary size and runtime memory usage), and avoiding +unnecessary work makes code run faster. Smaller code also tends to run faster +on modern hardware due to CPU cacheing: fitting your code into L1 cache is +great, and staying in L2 cache is still pretty good.</p> + +<p>A simple implementation usually takes up fewer lines of source code, +meaning more code can fit on the screen at once, meaning the programmer can +see more of it on the screen and thus keep more if in their head at once. +This helps code auditing and thus reduces bugs.</p> + +<p>Ken Thompson's maximum "when in doubt, use brute force" is an admonishment +to start with the simplest possible approach and only optimize as needed. +Although implementing a given set of features is the eventual purpose of +toybox, we choose to weight simplicity more heavily than anything else. +Complexity is what we spend to get features (and occasionally smaller size +or faster running time than the simplest possible implementation). Sometimes +a feature, speedup, or code shrink isn't worth the complexity cost. We want to +get "the best bang for the byte" we can, but sometimes being more explicit +is preferable to being clever enough to outsmart yourself. (Even the best +programmers are only human.)</p> + +<p>Environmental dependencies are a type of complexity, so needing other +packages to build or run is a big downside. For example, we don't use curses +when we can simply output ansi escape sequences and trust all terminal +programs written in the past 30 years to be able to support them. (A common +use case is to download a statically linked toybox binary to an arbitrary +Linux system, and use it in an otherwise unknown environment. It _must_ be +completely self-contained to support this.)</p> + <p><h1>Code style</h1></p> <p>Toybox source is formatted to be read with 4-space tab stops. Each file @@ -15,11 +50,37 @@ at the end of the function. Goto labels are never indented: they override the block structure of the file. Putting them at the left edge makes them easy to spot as overrides to the normal flow of control, which they are.</p> -<p>The primary goal of toybox is _simple_ code. Small is second, -speed and lots of features come in somewhere after that. Note that -environmental dependencies are a type of complexity, so needing other packages -to build or run is a big downside. For example, don't use curses when you can -output ansi escape sequences instead.</p> +<p><h1>Building Toybox:</h1></p> + +<p>Toybox is configured using the Kconfig language pioneered by the Linux +kernel, and adopted by many other projects (uClibc, OpenEmbedded, etc). +This generates a ".config" file containing the selected options, which +controls which features to enable when building toybox.</p> + +<p>Each configuration option has a default value. The defaults indicate the +"maximum sane configuration", I.E. if the feature defaults to "n" then it +either isn't complete or is a special-purpose option (such as debugging +code) that isn't intended for general purpose use.</p> + +<p>The standard build invocation is:</p> + +<ul> +<li>make defconfig #(or menuconfig)</li> +<li>make</li> +<li>make install</li> +</ul> + +<p>Type "make help" to see all available build options.</p> + +<p>The file "configure" contains a number of environment variable definitions +which influence the build, such as specifying which compiler to use or where +to install the resulting binaries. This file is included by the build, but +accepts existing definitions of the environment variables, so it may be sourced +or modified by the developer before building and the definitions exported +to the environment will take precedence.</p> + +<p>(To clarify: "configure" describes the build and installation environment, +".config" lists the features selected by defconfig/menuconfig.)</p> <p><h1>Infrastructure:</h1></p> @@ -46,7 +107,7 @@ files generated from other parts of the source code.</li> the toys directory. No other files need to be modified; the build extracts all the information it needs (such as command line arguments) from specially formatted comments and macros in the C file. (See the description of the -<a href="#generated">generated directory</a> for details.)</p> +<a href="#generated">"generated" directory</a> for details.)</p> <p>An easy way to start a new command is copy the file "hello.c" to the name of the new command, and modify this copy to implement the new command. @@ -341,6 +402,7 @@ instructions</a>.</p> </li> </ul> +<a name="generated" /> <p>The "generated/" directory contains files generated from other source code in toybox. All of these files can be recreated by the build system, although some (such as generated/help.h) are shipped in release versions to reduce |