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source: vbox/trunk/doc/VBox-MakefileGuidelines.cpp@ 76627

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1/* $Id: VBox-MakefileGuidelines.cpp 76553 2019-01-01 01:45:53Z vboxsync $ */
2/** @file
3 * VBox - Makefile Guidelines.
4 */
5
6/*
7 * Copyright (C) 2009-2019 Oracle Corporation
8 *
9 * This file is part of VirtualBox Open Source Edition (OSE), as
10 * available from http://www.virtualbox.org. This file is free software;
11 * you can redistribute it and/or modify it under the terms of the GNU
12 * General Public License (GPL) as published by the Free Software
13 * Foundation, in version 2 as it comes in the "COPYING" file of the
14 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
15 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
16 */
17
18/** @page pg_vbox_makefile_guidelines VBox Makefile Guidelines
19 *
20 * These guidelines apply to all the Makefile.kmk files in the tree.
21 * No exceptions.
22 *
23 * All these makefiles are ultimately the responsiblity of bird. Since there
24 * are currently more than three hundred files and the number is growing, they
25 * have to be very kept uniform or it will become very difficult to maintain
26 * them and impossible do bulk refactoring. Thus these guidelines have no bits
27 * that are optional unlike the coding guidelines, and should be thought of as
28 * rules rather than guidelines.
29 *
30 * Note! The guidelines do not apply to the non-kBuild makefiles found in the
31 * source tree, like the ones shipped in the SDK and the ones for the
32 * linux kernel modules.
33 *
34 *
35 * @section sec_vbox_makefile_guidelines_kbuild kBuild
36 *
37 * kBuild is way older than VirtualBox, at least as a concept, but the
38 * VirtualBox project was a push to get something done about it again. It's
39 * maintained by bird in his spare time because: "We don't make buildsystems, we
40 * make virtual machines". So, kBuild makes progress when there is spare time
41 * or when there is an urgent need for something.
42 *
43 * The kBuild docs are in the process of being written. The current items and
44 * their status per 2018-10-29:
45 * - kmk Quick Reference [completed]:
46 * http://svn.netlabs.org/kbuild/wiki/kmk%20Quick%20Reference
47 * - kBuild Quick Reference [just started]:
48 * http://svn.netlabs.org/kbuild/wiki/kBuild%20Quick%20Reference
49 *
50 * Local copies of the docs can be found in kBuild/docs, just keep in mind that
51 * they might be slightly behind the online version.
52 *
53 *
54 * @section sec_vbox_makefile_guidelines_example Example Makefiles
55 *
56 * Let me point to some good sample makefiles:
57 * - src/VBox/Additions/common/VBoxService/Makefile.kmk
58 * - src/VBox/Debugger/Makefile.kmk
59 * - src/VBox/Disassembler/Makefile.kmk
60 *
61 * And some bad ones:
62 * - src/lib/xpcom18a4/Makefile.kmk
63 * - src/recompiler/Makefile.kmk
64 * - src/VBox/Devices/Makefile.kmk
65 * - src/VBox/Main/Makefile.kmk
66 * - src/VBox/Runtime/Makefile.kmk
67 *
68 *
69 * @section sec_vbox_makefile_guidelines Guidelines
70 *
71 * First one really important fact:
72 *
73 * Everything is global because all makefiles
74 * are virtually one single makefile.
75 *
76 * The rules:
77 *
78 * - Using bits defined by a sub-makefile is fine, using anything defined
79 * by a parent, sibling, uncle, cousine, or remoter relatives is not
80 * Okay. It may break sub-tree building which is not acceptable.
81 *
82 * - Template names starts with VBox and are camel cased, no
83 * underscores or other separators. (Note this used to be all upper
84 * case, fixing this incomplete.)
85 *
86 * - Makefile variables shall be prefixed with VBOX or VB to avoid clashes
87 * with environment and kBuild variables.
88 *
89 * - Makefile variables are all upper cased and uses underscores to
90 * separate the words.
91 *
92 * - All variables are global. Make sure they are globally unique, but try
93 * not make them incredible long.
94 *
95 * - Makefile variables goes after the inclusion of the header and
96 * usually after including sub-makefiles.
97 *
98 * - Variables that are used by more than one makefile usually ends up
99 * in the monster file, Config.kmk. However, see if there are any
100 * sub-tree specific Config.kmk files that could do the job first.
101 *
102 * - Targets are lower or camel cased and as a rule the same as the
103 * resulting binary.
104 *
105 * - Install targets frequently have a -inst in their name, and a name that
106 * gives some idea what they install
107 *
108 * - Always use templates (mytarget_TEMPLATE = VBoxSomething).
109 *
110 * - Comment each target with a 3+ line block as seen in
111 * src/VBox/Debugger/Makefile.kmk.
112 *
113 * - No space between the comment block and the target definition.
114 *
115 * - Try fit all the custom recipes after the target they apply to.
116 *
117 * - Custom recipes that apply to more than one target should be placed at
118 * the bottom of the makefile, before the footer inclusion when possible.
119 *
120 * - Do NOT use custom recipes to install stuff, use install targets.
121 * Generate files to inst-target_0_OUTDIR. (Yes, there are a lot places
122 * where we don't do this yet.)
123 *
124 * - Always break SOURCES, LIBS, long target list and other lists the
125 * manner Debugger_SOURCES is broken into multiple lines in
126 * src/VBox/Debugger/Makefile.kmk. I.e. exactly one tab, the file name /
127 * list item, another space, the slash and then the newline.
128 *
129 * - Line continuation slashes shall never ever be aligned vertically (that
130 * always goes crooked sooner or later), but have exactly one space
131 * before them.
132 *
133 * - The last element of an broken list shall not have a slash-newline,
134 * otherwise we risk getting the next variable into the list.
135 *
136 * - When if'ed blocks come into play, we will only indent the conditional
137 * makefile directives (if, ifeq, ifneq, if1of, ifn1of, ifdef, ifndef,
138 * else, endif, ++), one space for each level. (Note! We used to indent
139 * non-directives, which made emacs upset as we'd have both tabs and
140 * spaces on as indentation on the same line. There are a lot of cases
141 * of this still around.)
142 *
143 * - \$(NO_SUCH_VARIABLE) should be when you need to put nothing somewhere,
144 * for instance to prevent inherting an attribute.
145 *
146 * - Always put the defines in the DEFS properties, never use the FLAGS
147 * properties for this. Doing so may screw up depenencies and object
148 * caches.
149 *
150 * - Mark each section and target of the file with a 3+ lines comment
151 * block.
152 *
153 * - Document variables that are not immediately obvious using double hash
154 * comments, doxygen style.
155 *
156 * - Each an every Makefile.kmk shall have a file header with Id, file
157 * description and copyright/license exactly like in the examples. (The
158 * SCM tool will complain if you don't.)
159 *
160 * - Multiple blank lines in a makefile is very seldom there without a
161 * reason and shall be preserved.
162 *
163 * - Inserting blank lines between target properties is all right if the
164 * target definition is long and/or crooked.
165 *
166 * - if1of and ifn1of shall always have a space after the comma, while ifeq
167 * and ifneq shall not. That way they are easier to tell apart.
168 *
169 * - Do a svn diff before committing makefile changes.
170 *
171 *
172 * @section sec_vbox_makefile_guidelines_reminders Helpful reminders
173 *
174 * - Do not be afraid to ask for help on IRC or in the defect you're
175 * working on. There are usually somebody around that know how to best do
176 * something.
177 *
178 * - Watch out for "Heads Up!" bugtracker messages concerning the build
179 * system.
180 *
181 * - To remove bits from a template you're using you have to create a new
182 * template that extends the existing one and creatively use
183 * \$(filter-out) or \$(patsubst).
184 *
185 * - You can build sub-trees.
186 *
187 * - You don't have to cd into sub-trees: kmk -C src/recompiler
188 *
189 * - You can build individual targets: kmk VBoxRT
190 *
191 * - Even install targets: kmk nobin
192 *
193 * - You can compile individual source files: kmk ConsoleImpl.o
194 *
195 * - You can tell kmk to continue on failure: kmk -k
196 *
197 * - You can tell kmk to run at low priority: kmk --nice
198 *
199 * - The --pretty-command-printing option is useful for seeing exactly
200 * what's passed to the tools.
201 *
202 * - You can invoke recipes in the root makefile more efficiently via the
203 * Maintenance.kmk file: kmk -f Maintenance.kmk incs
204 *
205 */
206
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