Mu - linux/bootstrap/000organization.cc

From 3350c34a74844e21ea69077e01efff3bae64bdcd Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Tue, 23 Mar 2021 17:31:08 -0700 Subject: . --- html/linux/bootstrap/000organization.cc.html | 227 +++++++++++++++++++++++++++ 1 file changed, 227 insertions(+) create mode 100644 html/linux/bootstrap/000organization.cc.html (limited to 'html/linux/bootstrap/000organization.cc.html') diff --git a/html/linux/bootstrap/000organization.cc.html b/html/linux/bootstrap/000organization.cc.html new file mode 100644 index 00000000..56125b37 --- /dev/null +++ b/html/linux/bootstrap/000organization.cc.html @@ -0,0 +1,227 @@ + + + + +Mu - linux/bootstrap/000organization.cc + + + + + + + + + + +https://github.com/akkartik/mu/blob/main/linux/bootstrap/000organization.cc +
+  1 //: You guessed right: the '000' prefix means you should start reading here.
+  2 //:
+  3 //: This project is set up to load all files with a numeric prefix. Just
+  4 //: create a new file and start hacking.
+  5 //:
+  6 //: The first few files (00*) are independent of what this program does, an
+  7 //: experimental skeleton that will hopefully make it both easier for others to
+  8 //: understand and more malleable, easier to rewrite and remould into radically
+  9 //: different shapes without breaking in subtle corner cases. The premise is
+ 10 //: that understandability and rewrite-friendliness are related in a virtuous
+ 11 //: cycle. Doing one well makes it easier to do the other.
+ 12 //:
+ 13 //: Lower down, this file contains a legal, bare-bones C++ program. It doesn't
+ 14 //: do anything yet; subsequent files will contain :(...) directives to insert
+ 15 //: lines into it. For example:
+ 16 //:   :(after "more events")
+ 17 //: This directive means: insert the following lines after a line in the
+ 18 //: program containing the words "more events".
+ 19 //:
+ 20 //: A simple tool is included to 'tangle' all the files together in sequence
+ 21 //: according to their directives into a single source file containing all the
+ 22 //: code for the project, and then feed the source file to the compiler.
+ 23 //: (It'll drop these comments starting with a '//:' prefix that only make
+ 24 //: sense before tangling.)
+ 25 //:
+ 26 //: Directives free up the programmer to order code for others to read rather
+ 27 //: than as forced by the computer or compiler. Each individual feature can be
+ 28 //: organized in a self-contained 'layer' that adds code to many different data
+ 29 //: structures and functions all over the program. The right decomposition into
+ 30 //: layers will let each layer make sense in isolation.
+ 31 //:
+ 32 //:   "If I look at any small part of it, I can see what is going on -- I don't
+ 33 //:   need to refer to other parts to understand what something is doing.
+ 34 //:
+ 35 //:   If I look at any large part in overview, I can see what is going on -- I
+ 36 //:   don't need to know all the details to get it.
+ 37 //:
+ 38 //:   Every level of detail is as locally coherent and as well thought-out as
+ 39 //:   any other level."
+ 40 //:
+ 41 //:       -- Richard Gabriel, "The Quality Without A Name"
+ 42 //:          (http://dreamsongs.com/Files/PatternsOfSoftware.pdf, page 42)
+ 43 //:
+ 44 //: Directives are powerful; they permit inserting or modifying any point in
+ 45 //: the program. Using them tastefully requires mapping out specific lines as
+ 46 //: waypoints for future layers to hook into. Often such waypoints will be in
+ 47 //: comments, capitalized to hint that other layers rely on their presence.
+ 48 //:
+ 49 //: A single waypoint might have many different code fragments hooking into
+ 50 //: it from all over the codebase. Use 'before' directives to insert
+ 51 //: code at a location in order, top to bottom, and 'after' directives to
+ 52 //: insert code in reverse order. By convention waypoints intended for insertion
+ 53 //: before begin with 'End'. Notice below how the layers line up above the "End
+ 54 //: Foo" waypoint.
+ 55 //:
+ 56 //:   File 001          File 002                File 003
+ 57 //:   ============      ===================     ===================
+ 58 //:   // Foo
+ 59 //:   ------------
+ 60 //:              <----  :(before "End Foo")
+ 61 //:                     ....
+ 62 //:                     ...
+ 63 //:   ------------
+ 64 //:              <----------------------------  :(before "End Foo")
+ 65 //:                                             ....
+ 66 //:                                             ...
+ 67 //:   // End Foo
+ 68 //:   ============
+ 69 //:
+ 70 //: Here's part of a layer in color: http://i.imgur.com/0eONnyX.png. Directives
+ 71 //: are shaded dark.
+ 72 //:
+ 73 //: Layers do more than just shuffle code around. In a well-organized codebase
+ 74 //: it should be possible to stop loading after any file/layer, build and run
+ 75 //: the program, and pass all tests for loaded features. (Relevant is
+ 76 //: http://youtube.com/watch?v=c8N72t7aScY, a scene from "2001: A Space
+ 77 //: Odyssey".) Get into the habit of running the included script called
+ 78 //: 'test_layers' before you commit any changes.
+ 79 //:
+ 80 //: This 'subsetting guarantee' ensures that this directory contains a
+ 81 //: cleaned-up narrative of the evolution of this codebase. Organizing
+ 82 //: autobiographically allows newcomers to rapidly orient themselves, reading
+ 83 //: the first few files to understand a simple gestalt of a program's core
+ 84 //: purpose and features, and later gradually working their way through other
+ 85 //: features as the need arises.
+ 86 //:
+ 87 //: Programmers shouldn't need to understand everything about a program to
+ 88 //: hack on it. But they shouldn't be prevented from a thorough understanding
+ 89 //: of each aspect either. The goal of layers is to reward curiosity.
+ 90 //:
+ 91 //: More information: http://akkartik.name/post/wart-layers
+ 92 
+ 93 // Includes
+ 94 // End Includes
+ 95 
+ 96 // Types
+ 97 // End Types
+ 98 
+ 99 // Function prototypes are auto-generated in the 'build' script; define your
+100 // functions in any order. Just be sure to declare each function header all on
+101 // one line, ending with the '{'. Our auto-generation scripts are too minimal
+102 // and simple-minded to handle anything else.
+103 #include "function_list"  // by convention, files ending with '_list' are auto-generated
+104 
+105 // Globals
+106 //
+107 // All statements in this section should always define a single variable on a
+108 // single line. The 'build' script will simple-mindedly auto-generate extern
+109 // declarations for them. Remember to define (not just declare) constants with
+110 // extern linkage in this section, since C++ global constants have internal
+111 // linkage by default.
+112 //
+113 // End Globals
+114 
+115 int main(int argc, char* argv[]) {
+116   atexit(reset);
+117   // we require a 32-bit little-endian system
+118   assert(sizeof(int) == 4);
+119   assert(sizeof(float) == 4);
+120   assert_little_endian();
+121 
+122   // End One-time Setup
+123 
+124   // Commandline Parsing
+125   // End Commandline Parsing
+126 
+127   // End Main
+128 
+129   return 0;
+130 }
+131 
+132 // Unit Tests
+133 // End Unit Tests
+134 
+135 //: our first directive; insert the following headers at the start of the program
+136 :(before "End Includes")
+137 #include <assert.h>
+138 #include <stdlib.h>
+139 
+140 //: Without directives or with the :(code) directive, lines get added at the
+141 //: end.
+142 //:
+143 //: Regardless of where functions are defined, we can call them anywhere we
+144 //: like as long as we format the function header in a specific way: put it
+145 //: all on a single line without indent, end the line with ') {' and no
+146 //: trailing whitespace. As long as functions uniformly start this way, our
+147 //: 'build' script contains a little command to automatically generate
+148 //: declarations for them.
+149 :(code)
+150 void reset() {
+151   // End Reset
+152 }
+153 
+154 void assert_little_endian() {
+155   const int x = 1;
+156   const char* y = reinterpret_cast<const char*>(&x);
+157   if (*y != 1) {
+158     cerr << "SubX requires a little-endian processor. Do you have Intel (or AMD or Atom) inside?\n";
+159     exit(1);
+160   }
+161 }
+162 :(before "End Includes")
+163 #include<iostream>
+164 using std::cerr;
+
+ + + -- cgit 1.4.1-2-gfad0