VBox-CodingGuidelines.cpp@ 76690

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1	/* $Id: VBox-CodingGuidelines.cpp 76553 2019-01-01 01:45:53Z vboxsync $ */
2	/** @file
3	* VBox - Coding Guidelines.
4	*/
5
6	/*
7	* Copyright (C) 2006-2019 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_guideline VBox Coding Guidelines
19	*
20	* The compulsory sections of these guidelines are to be followed in all of the
21	* VBox sources. Please note that local guidelines in parts of the VBox source
22	* tree may promote the optional ones to compulsory status. The VBox tree also
23	* contains some 3rd party sources where it is good to follow the local coding
24	* style while keeping these guidelines in mind.
25	*
26	* Contents:
27	* - @ref sec_vbox_guideline_compulsory
28	* - @ref sec_vbox_guideline_compulsory_sub64
29	* - @ref sec_vbox_guideline_compulsory_cppmain
30	* - @ref sec_vbox_guideline_compulsory_cppqtgui
31	* - @ref sec_vbox_guideline_compulsory_xslt
32	* - @ref sec_vbox_guideline_compulsory_doxygen
33	* - @ref sec_vbox_guideline_compulsory_guest
34	* - @ref sec_vbox_guideline_optional
35	* - @ref sec_vbox_guideline_optional_layout
36	* - @ref sec_vbox_guideline_optional_prefix
37	* - @ref sec_vbox_guideline_optional_misc
38	* - @ref sec_vbox_guideline_warnings
39	* - @ref sec_vbox_guideline_warnings_signed_unsigned_compare
40	* - @ref sec_vbox_guideline_svn
41	*
42	* Local guidelines overrides:
43	* - src/VBox/VMM/: @ref pg_vmm_guideline (src/VBox/VMM/Docs-CodingGuidelines.cpp)
44	* - src/VBox/ValidationKit/: @ref pg_validationkit_guideline (src/VBox/ValidationKit/ValidationKitCodingGuidelines.cpp)
45	* - src/VBox/Runtime/: All of @ref sec_vbox_guideline_optional is mandatory.
46	* - src/VBox/Main/: @ref sec_vbox_guideline_compulsory_cppmain
47	* - src/VBox/Frontends/VirtualBox/: @ref sec_vbox_guideline_compulsory_cppqtgui
48	*
49	*
50	* @section sec_vbox_guideline_compulsory Compulsory
51	*
52	* <ul>
53	*
54	* <li> The indentation size is 4 chars.
55	*
56	* <li> Tabs are only ever used in makefiles.
57	*
58	* <li> Use RT and VBOX types.
59	*
60	* <li> Use Runtime functions.
61	*
62	* <li> Use the standard bool, uintptr_t, intptr_t and [u]int[1-9+]_t types.
63	*
64	* <li> Avoid using plain unsigned and int.
65	*
66	* <li> Use static wherever possible. This makes the namespace less polluted
67	* and avoids nasty name clash problems which can occur, especially on
68	* Unix-like systems. (1) It also simplifies locating callers when
69	* changing it (single source file vs entire VBox tree).
70	*
71	* <li> Public names are of the form Domain[Subdomain[]]Method, using mixed
72	* casing to mark the words. The main domain is all uppercase.
73	* (Think like java, mapping domain and subdomain to packages/classes.)
74	*
75	* <li> Public names are always declared using the appropriate DECL macro. (2)
76	*
77	* <li> Internal names starts with a lowercased main domain.
78	*
79	* <li> Defines are all uppercase and separate words with underscore.
80	* This applies to enum values too.
81	*
82	* <li> Typedefs are all uppercase and contain no underscores to distinguish
83	* them from defines.
84	*
85	* <li> Pointer typedefs start with 'P'. If pointer to const then 'PC'.
86	*
87	* <li> Function typedefs start with 'FN'. If pointer to FN then 'PFN'.
88	*
89	* <li> All files are case sensitive.
90	*
91	* <li> Slashes are unix slashes ('/') runtime converts when necessary.
92	*
93	* <li> char strings are UTF-8.
94	*
95	* <li> Strings from any external source must be treated with utmost care as
96	* they do not have to be valid UTF-8. Only trust internal strings.
97	*
98	* <li> All functions return VBox status codes. There are three general
99	* exceptions from this:
100	*
101	* <ol>
102	* <li>Predicate functions. These are function which are boolean in
103	* nature and usage. They return bool. The function name will
104	* include 'Has', 'Is' or similar.
105	* <li>Functions which by nature cannot possibly fail.
106	* These return void.
107	* <li>"Get"-functions which return what they ask for.
108	* A get function becomes a "Query" function if there is any
109	* doubt about getting what is ask for.
110	* </ol>
111	*
112	* <li> VBox status codes have three subdivisions:
113	* <ol>
114	* <li> Errors, which are VERR_ prefixed and negative.
115	* <li> Warnings, which are VWRN_ prefixed and positive.
116	* <li> Informational, which are VINF_ prefixed and positive.
117	* </ol>
118	*
119	* <li> Platform/OS operation are generalized and put in the IPRT.
120	*
121	* <li> Other useful constructs are also put in the IPRT.
122	*
123	* <li> The code shall not cause compiler warnings. Check this on ALL
124	* the platforms.
125	*
126	* <li> The use of symbols leading with single or double underscores is
127	* forbidden as that intrudes on reserved compiler/system namespace. (3)
128	*
129	* <li> All files have file headers with $Id and a file tag which describes
130	* the file in a sentence or two.
131	* Note: Use the svn-ps.cmd/svn-ps.sh utility with the -a option to add
132	* new sources with keyword expansion and exporting correctly
133	* configured.
134	*
135	* <li> All public functions are fully documented in Doxygen style using the
136	* javadoc dialect (using the 'at' instead of the 'slash' as
137	* commandprefix.)
138	*
139	* <li> All structures in header files are described, including all their
140	* members. (Doxygen style, of course.)
141	*
142	* <li> All modules have a documentation '\@page' in the main source file
143	* which describes the intent and actual implementation.
144	*
145	* <li> Code which is doing things that are not immediately comprehensible
146	* shall include explanatory comments.
147	*
148	* <li> Documentation and comments are kept up to date.
149	*
150	* <li> Headers in /include/VBox shall not contain any slash-slash C++
151	* comments, only ANSI C comments!
152	*
153	* <li> Comments on \#else indicates what begins while the comment on a
154	* \#endif indicates what ended. Only add these when there are more than
155	* a few lines (6-10) of \#ifdef'ed code, otherwise they're just clutter.
156	*
157	* <li> \#ifdefs around a single function shall be tight, i.e. no empty
158	* lines between it and the function documentation and body.
159	*
160	* <li> \#ifdefs around more than one function shall be relaxed, i.e. leave at
161	* least one line before the first function's documentation comment and
162	* one line after the end of the last function.
163	*
164	* <li> No 'else' after if block ending with 'return', 'break', or 'continue'.
165	*
166	* <li> The term 'last' is inclusive, whereas the term 'end' is exclusive.
167	*
168	* <li> Go through all of this: https://www.slideshare.net/olvemaudal/deep-c/
169	*
170	* </ul>
171	*
172	* (1) It is common practice on Unix to have a single symbol namespace for an
173	* entire process. If one is careless symbols might be resolved in a
174	* different way that one expects, leading to weird problems.
175	*
176	* (2) This is common practice among most projects dealing with modules in
177	* shared libraries. The Windows / PE __declspect(import) and
178	* __declspect(export) constructs are the main reason for this.
179	* OTOH, we do perhaps have a bit too detailed graining of this in VMM...
180	*
181	* (3) There are guys out there grepping public sources for symbols leading with
182	* single and double underscores as well as gotos and other things
183	* considered bad practice. They'll post statistics on how bad our sources
184	* are on some mailing list, forum or similar.
185	*
186	*
187	* @subsection sec_vbox_guideline_compulsory_sub64 64-bit and 32-bit
188	*
189	* Here are some amendments which address 64-bit vs. 32-bit portability issues.
190	*
191	* Some facts first:
192	*
193	* <ul>
194	*
195	* <li> On 64-bit Windows the type long remains 32-bit. On nearly all other
196	* 64-bit platforms long is 64-bit.
197	*
198	* <li> On all 64-bit platforms we care about, int is 32-bit, short is 16 bit
199	* and char is 8-bit.
200	* (I don't know about any platforms yet where this isn't true.)
201	*
202	* <li> size_t, ssize_t, uintptr_t, ptrdiff_t and similar are all 64-bit on
203	* 64-bit platforms. (These are 32-bit on 32-bit platforms.)
204	*
205	* <li> There is no inline assembly support in the 64-bit Microsoft compilers.
206	*
207	* </ul>
208	*
209	* Now for the guidelines:
210	*
211	* <ul>
212	*
213	* <li> Never, ever, use int, long, ULONG, LONG, DWORD or similar to cast a
214	* pointer to integer. Use uintptr_t or intptr_t. If you have to use
215	* NT/Windows types, there is the choice of ULONG_PTR and DWORD_PTR.
216	*
217	* <li> Avoid where ever possible the use of the types 'long' and 'unsigned
218	* long' as these differs in size between windows and the other hosts
219	* (see above).
220	*
221	* <li> RT_OS_WINDOWS is defined to indicate Windows. Do not use __WIN32__,
222	* __WIN64__ and __WIN__ because they are all deprecated and scheduled
223	* for removal (if not removed already). Do not use the compiler
224	* defined _WIN32, _WIN64, or similar either. The bitness can be
225	* determined by testing ARCH_BITS.
226	* Example:
227	* @code
228	* #ifdef RT_OS_WINDOWS
229	* // call win32/64 api.
230	* #endif
231	* #ifdef RT_OS_WINDOWS
232	* # if ARCH_BITS == 64
233	* // call win64 api.
234	* # else // ARCH_BITS == 32
235	* // call win32 api.
236	* # endif // ARCH_BITS == 32
237	* #else // !RT_OS_WINDOWS
238	* // call posix api
239	* #endif // !RT_OS_WINDOWS
240	* @endcode
241	*
242	* <li> There are RT_OS_xxx defines for each OS, just like RT_OS_WINDOWS
243	* mentioned above. Use these defines instead of any predefined
244	* compiler stuff or defines from system headers.
245	*
246	* <li> RT_ARCH_X86 is defined when compiling for the x86 the architecture.
247	* Do not use __x86__, __X86__, __[Ii]386__, __[Ii]586__, or similar
248	* for this purpose.
249	*
250	* <li> RT_ARCH_AMD64 is defined when compiling for the AMD64 architecture.
251	* Do not use __AMD64__, __amd64__ or __x64_86__.
252	*
253	* <li> Take care and use size_t when you have to, esp. when passing a pointer
254	* to a size_t as a parameter.
255	*
256	* <li> Be wary of type promotion to (signed) integer. For example the
257	* following will cause u8 to be promoted to int in the shift, and then
258	* sign extended in the assignment 64-bit:
259	* @code
260	* uint8_t u8 = 0xfe;
261	* uint64_t u64 = u8 << 24;
262	* // u64 == 0xfffffffffe000000
263	* @endcode
264	*
265	* </ul>
266	*
267	* @subsection sec_vbox_guideline_compulsory_cppmain C++ guidelines for Main
268	*
269	* Since the Main API code is a large amount of C++ code, it is allowed but
270	* not required to use C++ style comments (as permanent comments, beyond the
271	* temporary use allowed by the general coding guideline). This is a weak
272	* preference, i.e. large scale comment style changes are not encouraged.
273	*
274	* Main is currently (2009) full of hard-to-maintain code that uses complicated
275	* templates. The new mid-term goal for Main is to have less custom templates
276	* instead of more for the following reasons:
277	*
278	* <ul>
279	*
280	* <li> Template code is harder to read and understand. Custom templates create
281	* territories which only the code writer understands.
282	*
283	* <li> Errors in using templates create terrible C++ compiler messages.
284	*
285	* <li> Template code is really hard to look at in a debugger.
286	*
287	* <li> Templates slow down the compiler a lot.
288	*
289	* </ul>
290	*
291	* In particular, the following bits should be considered deprecated and should
292	* NOT be used in new code:
293	*
294	* <ul>
295	*
296	* <li> everything in include/iprt/cpputils.h (auto_ref_ptr, exception_trap_base,
297	* char_auto_ptr and friends)
298	*
299	* </ul>
300	*
301	* Generally, in many cases, a simple class with a proper destructor can achieve
302	* the same effect as a 1,000-line template include file, and the code is
303	* much more accessible that way.
304	*
305	* Using standard STL templates like std::list, std::vector and std::map is OK.
306	* Exceptions are:
307	*
308	* <ul>
309	*
310	* <li> Guest Additions because we don't want to link against libstdc++ there.
311	*
312	* <li> std::string should not be used because we have iprt::MiniString and
313	* com::Utf8Str which can convert efficiently with COM's UTF-16 strings.
314	*
315	* <li> std::auto_ptr<> in general; that part of the C++ standard is just broken.
316	* Write a destructor that calls delete.
317	*
318	* </ul>
319	*
320	* @subsection sec_vbox_guideline_compulsory_cppqtgui C++ guidelines for the Qt GUI
321	*
322	* The Qt GUI is currently (2010) on its way to become more compatible to the
323	* rest of VirtualBox coding style wise. From now on, all the coding style
324	* rules described in this file are also mandatory for the Qt GUI. Additionally
325	* the following rules should be respected:
326	*
327	* <ul>
328	*
329	* <li> GUI classes which correspond to GUI tasks should be prefixed by UI (no VBox anymore)
330	*
331	* <li> Classes which extents some of the Qt classes should be prefix by QI
332	*
333	* <li> General task classes should be prefixed by C
334	*
335	* <li> Slots are prefixed by slt -> sltName
336	*
337	* <li> Signals are prefixed by sig -> sigName
338	*
339	* <li> Use Qt classes for lists, strings and so on, the use of STL classes should
340	* be avoided
341	*
342	* <li> All files like .cpp, .h, .ui, which belong together are located in the
343	* same directory and named the same
344	*
345	* </ul>
346	*
347	*
348	* @subsection sec_vbox_guideline_compulsory_xslt XSLT
349	*
350	* XSLT (eXtensible Stylesheet Language Transformations) is used quite a bit in
351	* the Main API area of VirtualBox to generate sources and bindings to that API.
352	* There are a couple of common pitfalls worth mentioning:
353	*
354	* <ul>
355	*
356	* <li> Never do repeated //interface[\@name=...] and //enum[\@name=...] lookups
357	* because they are expensive. Instead delcare xsl:key elements for these
358	* searches and do the lookup using the key() function. xsltproc uses
359	* (per current document) hash tables for each xsl:key, i.e. very fast.
360	*
361	* <li> When output type is 'text' make sure to call xsltprocNewlineOutputHack
362	* from typemap-shared.inc.xsl every few KB of output, or xsltproc will
363	* end up wasting all the time reallocating the output buffer.
364	*
365	* </ul>
366	*
367	*
368	* @subsection sec_vbox_guideline_compulsory_doxygen Doxygen Comments
369	*
370	* As mentioned above, we shall use doxygen/javadoc style commenting of public
371	* functions, typedefs, classes and such. It is mandatory to use this style
372	* everywhere!
373	*
374	* A couple of hints on how to best write doxygen comments:
375	*
376	* <ul>
377	*
378	* <li> A good class, method, function, structure or enum doxygen comment
379	* starts with a one line sentence giving a brief description of the
380	* item. Details comes in a new paragraph (after blank line).
381	*
382	* <li> Except for list generators like \@todo, \@cfgm, \@gcfgm and others,
383	* all doxygen comments are related to things in the code. So, for
384	* instance you DO NOT add a doxygen \@note comment in the middle of a
385	* because you've got something important to note, you add a normal
386	* comment like 'Note! blah, very importan blah!'
387	*
388	* <li> We do NOT use TODO/XXX/BUGBUG or similar markers in the code to flag
389	* things needing fixing later, we always use \@todo doxygen comments.
390	*
391	* <li> There is no colon after the \@todo. And it is ALWAYS in a doxygen
392	* comment.
393	*
394	* <li> The \@retval tag is used to explain status codes a method/function may
395	* returns. It is not used to describe output parameters, that is done
396	* using the \@param or \@param[out] tag.
397	*
398	* </ul>
399	*
400	* See https://www.stack.nl/~dimitri/doxygen/manual/index.html for the official
401	* doxygen documention.
402	*
403	*
404	*
405	* @subsection sec_vbox_guideline_compulsory_guest Handling of guest input
406	*
407	* First, guest input should ALWAYS be consider to be TOXIC and constructed with
408	* MALICIOUS intent! Max paranoia level!
409	*
410	* Second, when getting inputs from memory shared with the guest, be EXTREMELY
411	* careful to not re-read input from shared memory after validating it, because
412	* that will create TOCTOU problems. So, after reading input from shared memory
413	* always use the RT_UNTRUSTED_NONVOLATILE_COPY_FENCE() macro. For more details
414	* on TOCTOU: https://en.wikipedia.org/wiki/Time_of_check_to_time_of_use
415	*
416	* Thirdly, considering the recent speculation side channel issues, spectre v1
417	* in particular, we would like to be ready for future screwups. This means
418	* having input validation in a separate block of code that ends with one (or
419	* more) RT_UNTRUSTED_VALIDATED_FENCE().
420	*
421	* So the rules:
422	*
423	* <ul>
424	*
425	* <li> Mark all pointers to shared memory with RT_UNTRUSTED_VOLATILE_GUEST.
426	*
427	* <li> Copy volatile data into local variables or heap before validating
428	* them (see RT_COPY_VOLATILE() and RT_BCOPY_VOLATILE().
429	*
430	* <li> Place RT_UNTRUSTED_NONVOLATILE_COPY_FENCE() after a block copying
431	* volatile data.
432	*
433	* <li> Always validate untrusted inputs in a block ending with a
434	* RT_UNTRUSTED_VALIDATED_FENCE().
435	*
436	* <li> Use the ASSERT_GUEST_XXXX macros from VBox/AssertGuest.h to validate
437	* guest input. (Do NOT use iprt/assert.h macros.)
438	*
439	* <li> Validation of an input B may require using another input A to look up
440	* some data, in which case its necessary to insert an
441	* RT_UNTRUSTED_VALIDATED_FENCE() after validating A and before A is used
442	* for the lookup.
443	*
444	* For example A is a view identifier, idView, and B is an offset into
445	* the view's framebuffer area, offView. To validate offView (B) it is
446	* necessary to get the size of the views framebuffer region:
447	* @code
448	* uint32_t const idView = pReq->idView; // A
449	* uint32_t const offView = pReq->offView; // B
450	* RT_UNTRUSTED_NONVOLATILE_COPY_FENCE();
451	*
452	* ASSERT_GUEST_RETURN(idView < pThis->cView,
453	* VERR_INVALID_PARAMETER);
454	* RT_UNTRUSTED_VALIDATED_FENCE();
455	* const MYVIEW *pView = &pThis->aViews[idView];
456	* ASSERT_GUEST_RETURN(offView < pView->cbFramebufferArea,
457	* VERR_OUT_OF_RANGE);
458	* RT_UNTRUSTED_VALIDATED_FENCE();
459	* @endcode
460	*
461	* <li> Take care to make sure input check are not subject to integer overflow problems.
462	*
463	* For instance when validating an area, you must not just add cbDst + offDst
464	* and check against pThis->offEnd or something like that. Rather do:
465	* @code
466	* uint32_t const offDst = pReq->offDst;
467	* uint32_t const cbDst = pReq->cbDst;
468	* RT_UNTRUSTED_NONVOLATILE_COPY_FENCE();
469	*
470	* ASSERT_GUEST_RETURN( cbDst <= pThis->cbSrc
471	* && offDst < pThis->cbSrc - cbDst,
472	* VERR_OUT_OF_RANGE);
473	* RT_UNTRUSTED_VALIDATED_FENCE();
474	* @endcode
475	*
476	* <li> Input validation does not only apply to shared data cases, but also to
477	* I/O port and MMIO handlers.
478	*
479	* <li> Ditto for kernel drivers working with usermode inputs.
480	*
481	* </ul>
482	*
483	*
484	* Problem patterns:
485	* - https://en.wikipedia.org/wiki/Time_of_check_to_time_of_use
486	* - https://googleprojectzero.blogspot.de/2018/01/reading-privileged-memory-with-side.html
487	* (Variant 1 only).
488	* - https://en.wikipedia.org/wiki/Integer_overflow
489	*
490	*
491	*
492	* @section sec_vbox_guideline_optional Optional
493	*
494	* First part is the actual coding style and all the prefixes. The second part
495	* is a bunch of good advice.
496	*
497	*
498	* @subsection sec_vbox_guideline_optional_layout The code layout
499	*
500	* <ul>
501	*
502	* <li> Max line length is 130 chars. Exceptions are table-like
503	* code/initializers and Log*() statements (don't waste unnecessary
504	* vertical space on debug logging).
505	*
506	* <li> Comments should try stay within the usual 80 columns as these are
507	* denser and too long lines may be harder to read.
508	*
509	* <li> Curly brackets are not indented. Example:
510	* @code
511	* if (true)
512	* {
513	* Something1();
514	* Something2();
515	* }
516	* else
517	* {
518	* SomethingElse1().
519	* SomethingElse2().
520	* }
521	* @endcode
522	*
523	* <li> Space before the parentheses when it comes after a C keyword.
524	*
525	* <li> No space between argument and parentheses. Exception for complex
526	* expression. Example:
527	* @code
528	* if (PATMR3IsPatchGCAddr(pVM, GCPtr))
529	* @endcode
530	*
531	* <li> The else of an if is always the first statement on a line. (No curly
532	* stuff before it!)
533	*
534	* <li> else and if go on the same line if no { compound statement }
535	* follows the if. Example:
536	* @code
537	* if (fFlags & MYFLAGS_1)
538	* fFlags &= ~MYFLAGS_10;
539	* else if (fFlags & MYFLAGS_2)
540	* {
541	* fFlags &= ~MYFLAGS_MASK;
542	* fFlags \|= MYFLAGS_5;
543	* }
544	* else if (fFlags & MYFLAGS_3)
545	* @endcode
546	*
547	* <li> Slightly complex boolean expressions are split into multiple lines,
548	* putting the operators first on the line and indenting it all according
549	* to the nesting of the expression. The purpose is to make it as easy as
550	* possible to read. Example:
551	* @code
552	* if ( RT_SUCCESS(rc)
553	* \|\| (fFlags & SOME_FLAG))
554	* @endcode
555	*
556	* <li> When 'if' or 'while' statements gets long, the closing parentheses
557	* goes right below the opening parentheses. This may be applied to
558	* sub-expression. Example:
559	* @code
560	* if ( RT_SUCCESS(rc)
561	* \|\| ( fSomeStuff
562	* && fSomeOtherStuff
563	* && fEvenMoreStuff
564	* )
565	* \|\| SomePredicateFunction()
566	* )
567	* {
568	* ...
569	* }
570	* @endcode
571	*
572	* <li> The case is indented from the switch (to avoid having the braces for
573	* the 'case' at the same level as the 'switch' statement).
574	*
575	* <li> If a case needs curly brackets they contain the entire case, are not
576	* indented from the case, and the break or return is placed inside them.
577	* Example:
578	* @code
579	* switch (pCur->eType)
580	* {
581	* case PGMMAPPINGTYPE_PAGETABLES:
582	* {
583	* unsigned iPDE = pCur->GCPtr >> PGDIR_SHIFT;
584	* unsigned iPT = (pCur->GCPtrEnd - pCur->GCPtr) >> PGDIR_SHIFT;
585	* while (iPT-- > 0)
586	* if (pPD->a[iPDE + iPT].n.u1Present)
587	* return VERR_HYPERVISOR_CONFLICT;
588	* break;
589	* }
590	* }
591	* @endcode
592	*
593	* <li> In a do while construction, the while is on the same line as the
594	* closing "}" if any are used.
595	* Example:
596	* @code
597	* do
598	* {
599	* stuff;
600	* i--;
601	* } while (i > 0);
602	* @endcode
603	*
604	* <li> Comments are in C style. C++ style comments are used for temporary
605	* disabling a few lines of code.
606	*
607	* <li> No unnecessary parentheses in expressions (just don't over do this
608	* so that gcc / msc starts bitching). Find a correct C/C++ operator
609	* precedence table if needed.
610	*
611	* <li> 'for (;;)' is preferred over 'while (true)' and 'while (1)'.
612	*
613	* <li> Parameters are indented to the start parentheses when breaking up
614	* function calls, declarations or prototypes. (This is in line with
615	* how 'if', 'for' and 'while' statements are done as well.) Example:
616	* @code
617	* RTPROCESS hProcess;
618	* int rc = RTProcCreateEx(papszArgs[0],
619	* papszArgs,
620	* RTENV_DEFAULT,
621	* fFlags,
622	* NULL, // phStdIn
623	* NULL, // phStdOut
624	* NULL, // phStdErr
625	* NULL, // pszAsUser
626	* NULL, // pszPassword
627	* &hProcess);
628	* @endcode
629	*
630	* <li> That Dijkstra is dead is no excuse for using gotos.
631	*
632	* <li> Using do-while-false loops to avoid gotos is considered very bad form.
633	* They create hard to read code. They tend to be either too short (i.e.
634	* pointless) or way to long (split up the function already), making
635	* tracking the state is difficult and prone to bugs. Also, they cause
636	* the compiler to generate suboptimal code, because the break branches
637	* are by preferred over the main code flow (MSC has no branch hinting!).
638	* Instead, do make use the 130 columns (i.e. nested ifs) and split
639	* the code up into more functions!
640	*
641	* <li> Avoid code like
642	* @code
643	* int foo;
644	* int rc;
645	* ...
646	* rc = FooBar();
647	* if (RT_SUCCESS(rc))
648	* {
649	* foo = getFoo();
650	* ...
651	* pvBar = RTMemAlloc(sizeof(*pvBar));
652	* if (!pvBar)
653	* rc = VERR_NO_MEMORY;
654	* }
655	* if (RT_SUCCESS(rc))
656	* {
657	* buzz = foo;
658	* ...
659	* }
660	* @endcode
661	* The intention of such code is probably to save some horizontal space
662	* but unfortunately it's hard to read and the scope of certain varables
663	* (e.g. foo in this example) is not optimal. Better use the following
664	* style:
665	* @code
666	* int rc;
667	* ...
668	* rc = FooBar();
669	* if (RT_SUCCESS(rc))
670	* {
671	* int foo = getFoo();
672	* ...
673	* pvBar = RTMemAlloc(sizeof(*pvBar));
674	* if (pvBar)
675	* {
676	* buzz = foo;
677	* ...
678	* }
679	* else
680	* rc = VERR_NO_MEMORY;
681	* }
682	* @endcode
683	*
684	* </ul>
685	*
686	* @subsection sec_vbox_guideline_optional_prefix Variable / Member Prefixes
687	*
688	* Prefixes are meant to provide extra context clues to a variable/member, we
689	* therefore avoid using prefixes that just indicating the type if a better
690	* choice is available.
691	*
692	*
693	* The prefixes:
694	*
695	* <ul>
696	*
697	* <li> The 'g_' (or 'g') prefix means a global variable, either on file or module level.
698	*
699	* <li> The 's_' (or 's') prefix means a static variable inside a function or
700	* class. This is not used for static variables on file level, use 'g_'
701	* for those (logical, right).
702	*
703	* <li> The 'm_' (or 'm') prefix means a class data member.
704	*
705	* In new code in Main, use "m_" (and common sense). As an exception,
706	* in Main, if a class encapsulates its member variables in an anonymous
707	* structure which is declared in the class, but defined only in the
708	* implementation (like this: 'class X { struct Data; Data *m; }'), then
709	* the pointer to that struct is called 'm' itself and its members then
710	* need no prefix, because the members are accessed with 'm->member'
711	* already which is clear enough.
712	*
713	* <li> The 'a_' prefix means a parameter (argument) variable. This is
714	* sometimes written 'a' in parts of the source code that does not use
715	* the array prefix.
716	*
717	* <li> The 'p' prefix means pointer. For instance 'pVM' is pointer to VM.
718	*
719	* <li> The 'r' prefix means that something is passed by reference.
720	*
721	* <li> The 'k' prefix means that something is a constant. For instance
722	* 'enum { kStuff };'. This is usually not used in combination with
723	* 'p', 'r' or any such thing, it's main main use is to make enums
724	* easily identifiable.
725	*
726	* <li> The 'a' prefix means array. For instance 'aPages' could be read as
727	* array of pages.
728	*
729	* <li> The 'c' prefix means count. For instance 'cbBlock' could be read,
730	* count of bytes in block. (1)
731	*
732	* <li> The 'cx' prefix means width (count of 'x' units).
733	*
734	* <li> The 'cy' prefix means height (count of 'y' units).
735	*
736	* <li> The 'x', 'y' and 'z' prefix refers to the x-, y- , and z-axis
737	* respectively.
738	*
739	* <li> The 'off' prefix means offset.
740	*
741	* <li> The 'i' or 'idx' prefixes usually means index. Although the 'i' one
742	* can sometimes just mean signed integer.
743	*
744	* <li> The 'i[1-9]+' prefix means a fixed bit size variable. Frequently
745	* used with the int[1-9]+_t types where the width is really important.
746	* In most cases 'i' is more appropriate. [type]
747	*
748	* <li> The 'e' (or 'enm') prefix means enum.
749	*
750	* <li> The 'u' prefix usually means unsigned integer. Exceptions follows.
751	*
752	* <li> The 'u[1-9]+' prefix means a fixed bit size variable. Frequently
753	* used with the uint[1-9]+_t types and with bitfields where the width is
754	* really important. In most cases 'u' or 'b' (byte) would be more
755	* appropriate. [type]
756	*
757	* <li> The 'b' prefix means byte or bytes. [type]
758	*
759	* <li> The 'f' prefix means flags. Flags are unsigned integers of some kind
760	* or booleans.
761	*
762	* <li> TODO: need prefix for real float. [type]
763	*
764	* <li> The 'rd' prefix means real double and is used for 'double' variables.
765	* [type]
766	*
767	* <li> The 'lrd' prefix means long real double and is used for 'long double'
768	* variables. [type]
769	*
770	* <li> The 'ch' prefix means a char, the (signed) char type. [type]
771	*
772	* <li> The 'wc' prefix means a wide/windows char, the RTUTF16 type. [type]
773	*
774	* <li> The 'uc' prefix means a Unicode Code point, the RTUNICP type. [type]
775	*
776	* <li> The 'uch' prefix means unsigned char. It's rarely used. [type]
777	*
778	* <li> The 'sz' prefix means zero terminated character string (array of
779	* chars). (UTF-8)
780	*
781	* <li> The 'wsz' prefix means zero terminated wide/windows character string
782	* (array of RTUTF16).
783	*
784	* <li> The 'usz' prefix means zero terminated Unicode string (array of
785	* RTUNICP).
786	*
787	* <li> The 'str' prefix means C++ string; either a std::string or, in Main,
788	* a Utf8Str or, in Qt, a QString. When used with 'p', 'r', 'a' or 'c'
789	* the first letter should be capitalized.
790	*
791	* <li> The 'bstr' prefix, in Main, means a UTF-16 Bstr. When used with 'p',
792	* 'r', 'a' or 'c' the first letter should be capitalized.
793	*
794	* <li> The 'pfn' prefix means pointer to function. Common usage is 'pfnCallback'
795	* and such like.
796	*
797	* <li> The 'psz' prefix is a combination of 'p' and 'sz' and thus means
798	* pointer to a zero terminated character string. (UTF-8)
799	*
800	* <li> The 'pcsz' prefix is used to indicate constant string pointers in
801	* parts of the code. Most code uses 'psz' for const and non-const
802	* string pointers, so please ignore this one.
803	*
804	* <li> The 'l' prefix means (signed) long. We try avoid using this,
805	* expecially with the 'LONG' types in Main as these are not 'long' on
806	* 64-bit non-Windows platforms and can cause confusion. Alternatives:
807	* 'i' or 'i32'. [type]
808	*
809	* <li> The 'ul' prefix means unsigned long. We try avoid using this,
810	* expecially with the 'ULONG' types in Main as these are not 'unsigned
811	* long' on 64-bit non-Windows platforms and can cause confusion.
812	* Alternatives: 'u' or 'u32'. [type]
813	*
814	* </ul>
815	*
816	* (1) Except in the occasional 'pcsz' prefix, the 'c' prefix is never ever
817	* used in the meaning 'const'.
818	*
819	*
820	* @subsection sec_vbox_guideline_optional_misc Misc / Advice / Stuff
821	*
822	* <ul>
823	*
824	* <li> When writing code think as the reader.
825	*
826	* <li> When writing code think as the compiler. (2)
827	*
828	* <li> When reading code think as if it's full of bugs - find them and fix them.
829	*
830	* <li> Pointer within range tests like:
831	* @code
832	* if ((uintptr_t)pv >= (uintptr_t)pvBase && (uintptr_t)pv < (uintptr_t)pvBase + cbRange)
833	* @endcode
834	* Can also be written as (assuming cbRange unsigned):
835	* @code
836	* if ((uintptr_t)pv - (uintptr_t)pvBase < cbRange)
837	* @endcode
838	* Which is shorter and potentially faster. (1)
839	*
840	* <li> Avoid unnecessary casting. All pointers automatically cast down to
841	* void *, at least for non class instance pointers.
842	*
843	* <li> It's very very bad practise to write a function larger than a
844	* screen full (1024x768) without any comprehensibility and explaining
845	* comments.
846	*
847	* <li> More to come....
848	*
849	* </ul>
850	*
851	* (1) Important, be very careful with the casting. In particular, note that
852	* a compiler might treat pointers as signed (IIRC).
853	*
854	* (2) "A really advanced hacker comes to understand the true inner workings of
855	* the machine - he sees through the language he's working in and glimpses
856	* the secret functioning of the binary code - becomes a Ba'al Shem of
857	* sorts." (Neal Stephenson "Snow Crash")
858	*
859	*
860	*
861	* @section sec_vbox_guideline_warnings Compiler Warnings
862	*
863	* The code should when possible compile on all platforms and compilers without any
864	* warnings. That's a nice idea, however, if it means making the code harder to read,
865	* less portable, unreliable or similar, the warning should not be fixed.
866	*
867	* Some of the warnings can seem kind of innocent at first glance. So, let's take the
868	* most common ones and explain them.
869	*
870	*
871	* @subsection sec_vbox_guideline_warnings_signed_unsigned_compare Signed / Unsigned Compare
872	*
873	* GCC says: "warning: comparison between signed and unsigned integer expressions"
874	* MSC says: "warning C4018: '<\|<=\|==\|>=\|>' : signed/unsigned mismatch"
875	*
876	* The following example will not output what you expect:
877	@code
878	#include <stdio.h>
879	int main()
880	{
881	signed long a = -1;
882	unsigned long b = 2294967295;
883	if (a < b)
884	printf("%ld < %lu: true\n", a, b);
885	else
886	printf("%ld < %lu: false\n", a, b);
887	return 0;
888	}
889	@endcode
890	* If I understood it correctly, the compiler will convert a to an
891	* unsigned long before doing the compare.
892	*
893	*
894	*
895	* @section sec_vbox_guideline_svn Subversion Commit Rules
896	*
897	*
898	* Before checking in:
899	*
900	* <ul>
901	*
902	* <li> Check Tinderbox and make sure the tree is green across all platforms. If it's
903	* red on a platform, don't check in. If you want, warn in the \#vbox channel and
904	* help make the responsible person fix it.
905	* NEVER CHECK IN TO A BROKEN BUILD.
906	*
907	* <li> When checking in keep in mind that a commit is atomic and that the Tinderbox and
908	* developers are constantly checking out the tree. Therefore do not split up the
909	* commit unless it's into 100% independent parts. If you need to split it up in order
910	* to have sensible commit comments, make the sub-commits as rapid as possible.
911	*
912	* <li> If you make a user visible change, such as fixing a reported bug,
913	* make sure you add an entry to doc/manual/user_ChangeLogImpl.xml.
914	*
915	* <li> If you are adding files make sure set the right attributes.
916	* svn-ps.sh/cmd was created for this purpose, please make use of it.
917	*
918	* </ul>
919	*
920	* After checking in:
921	*
922	* <ul>
923	*
924	* <li> After checking-in, you watch Tinderbox until your check-ins clear. You do not
925	* go home. You do not sleep. You do not log out or experiment with drugs. You do
926	* not become unavailable. If you break the tree, add a comment saying that you're
927	* fixing it. If you can't fix it and need help, ask in the \#innotek channel or back
928	* out the change.
929	*
930	* </ul>
931	*
932	* (Inspired by mozilla tree rules.)
933	*
934	*
935	*/
936

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