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diff --git a/doc/VBox-CodingGuidelines.cpp b/doc/VBox-CodingGuidelines.cpp new file mode 100644 index 00000000..a7117af7 --- /dev/null +++ b/doc/VBox-CodingGuidelines.cpp @@ -0,0 +1,614 @@ +/* $Id: VBox-CodingGuidelines.cpp $ */ +/** @file + * VBox - Coding Guidelines. + */ + +/* + * Copyright (C) 2006-2009 Oracle Corporation + * + * This file is part of VirtualBox Open Source Edition (OSE), as + * available from http://www.virtualbox.org. This file is free software; + * you can redistribute it and/or modify it under the terms of the GNU + * General Public License (GPL) as published by the Free Software + * Foundation, in version 2 as it comes in the "COPYING" file of the + * VirtualBox OSE distribution. VirtualBox OSE is distributed in the + * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind. + */ + +/** @page pg_vbox_guideline VBox Coding Guidelines + * + * The VBox Coding guidelines are followed by all of VBox with the exception of + * qemu. Qemu is using whatever the frenchman does. + * + * There are a few compulsory rules and a bunch of optional ones. The following + * sections will describe these in details. In addition there is a section of + * Subversion 'rules'. + * + * + * + * @section sec_vbox_guideline_compulsory Compulsory + * + * + * - The indentation size is 4 chars. + * + * - Tabs are only ever used in makefiles. + * + * - Use RT and VBOX types. + * + * - Use Runtime functions. + * + * - Use the standard bool, uintptr_t, intptr_t and [u]int[1-9+]_t types. + * + * - Avoid using plain unsigned and int. + * + * - Use static wherever possible. This makes the namespace less polluted + * and avoids nasty name clash problems which can occur, especially on + * Unix-like systems. (1) + * + * - Public names are of the form Domain[Subdomain[]]Method, using mixed + * casing to mark the words. The main domain is all uppercase. + * (Think like java, mapping domain and subdomain to packages/classes.) + * + * - Public names are always declared using the appropriate DECL macro. (2) + * + * - Internal names starts with a lowercased main domain. + * + * - Defines are all uppercase and separate words with underscore. + * This applies to enum values too. + * + * - Typedefs are all uppercase and contain no underscores to distinguish + * them from defines. + * + * - Pointer typedefs start with 'P'. If pointer to const then 'PC'. + * + * - Function typedefs start with 'FN'. If pointer to FN then 'PFN'. + * + * - All files are case sensitive. + * + * - Slashes are unix slashes ('/') runtime converts when necessary. + * + * - char strings are UTF-8. + * + * - All functions return VBox status codes. There are three general + * exceptions from this: + * -# Predicate functions. These are function which are boolean in + * nature and usage. They return bool. The function name will + * include 'Has', 'Is' or similar. + * -# Functions which by nature cannot possibly fail. + * These return void. + * -# "Get"-functions which return what they ask for. + * A get function becomes a "Query" function if there is any + * doubt about getting what is ask for. + * + * - VBox status codes have three subdivisions: + * -# Errors, which are VERR_ prefixed and negative. + * -# Warnings, which are VWRN_ prefixed and positive. + * -# Informational, which are VINF_ prefixed and positive. + * + * - Platform/OS operation are generalized and put in the IPRT. + * + * - Other useful constructs are also put in the IPRT. + * + * - The code shall not cause compiler warnings. Check this on ALL + * the platforms. + * + * - All files have file headers with $Id and a file tag which describes + * the file in a sentence or two. + * Note: Remember to enable keyword expansion when adding files to svn. + * + * - All public functions are fully documented in Doxygen style using the + * javadoc dialect (using the 'at' instead of the 'slash' as + * commandprefix.) + * + * - All structures in header files are described, including all their + * members. + * + * - All modules have a documentation 'page' in the main source file which + * describes the intent and actual implementation. + * + * - Code which is doing things that are not immediately comprehensible + * shall include explanatory comments. + * + * - Documentation and comments are kept up to date. + * + * - Headers in /include/VBox shall not contain any slash-slash C++ + * comments, only ANSI C comments! + * + * - Comments on \#else indicates what begins while the comment on a + * \#endif indicates what ended. + * + * + * (1) It is common practice on Unix to have a single symbol namespace for an + * entire process. If one is careless symbols might be resolved in a + * different way that one expects, leading to weird problems. + * + * (2) This is common practice among most projects dealing with modules in + * shared libraries. The Windows / PE __declspect(import) and + * __declspect(export) constructs are the main reason for this. + * OTOH, we do perhaps have a bit too detailed graining of this in VMM... + * + * + * @subsection sec_vbox_guideline_compulsory_sub64 64-bit and 32-bit + * + * Here are some amendments which address 64-bit vs. 32-bit portability issues. + * + * Some facts first: + * + * - On 64-bit Windows the type long remains 32-bit. On nearly all other + * 64-bit platforms long is 64-bit. + * + * - On all 64-bit platforms we care about, int is 32-bit, short is 16 bit + * and char is 8-bit. + * (I don't know about any platforms yet where this isn't true.) + * + * - size_t, ssize_t, uintptr_t, ptrdiff_t and similar are all 64-bit on + * 64-bit platforms. (These are 32-bit on 32-bit platforms.) + * + * - There is no inline assembly support in the 64-bit Microsoft compilers. + * + * + * Now for the guidelines: + * + * - Never, ever, use int, long, ULONG, LONG, DWORD or similar to cast a + * pointer to integer. Use uintptr_t or intptr_t. If you have to use + * NT/Windows types, there is the choice of ULONG_PTR and DWORD_PTR. + * + * - RT_OS_WINDOWS is defined to indicate Windows. Do not use __WIN32__, + * __WIN64__ and __WIN__ because they are all deprecated and scheduled + * for removal (if not removed already). Do not use the compiler + * defined _WIN32, _WIN64, or similar either. The bitness can be + * determined by testing ARCH_BITS. + * Example: + * @code + * #ifdef RT_OS_WINDOWS + * // call win32/64 api. + * #endif + * #ifdef RT_OS_WINDOWS + * # if ARCH_BITS == 64 + * // call win64 api. + * # else // ARCH_BITS == 32 + * // call win32 api. + * # endif // ARCH_BITS == 32 + * #else // !RT_OS_WINDOWS + * // call posix api + * #endif // !RT_OS_WINDOWS + * @endcode + * + * - There are RT_OS_xxx defines for each OS, just like RT_OS_WINDOWS + * mentioned above. Use these defines instead of any predefined + * compiler stuff or defines from system headers. + * + * - RT_ARCH_X86 is defined when compiling for the x86 the architecture. + * Do not use __x86__, __X86__, __[Ii]386__, __[Ii]586__, or similar + * for this purpose. + * + * - RT_ARCH_AMD64 is defined when compiling for the AMD64 architecture. + * Do not use __AMD64__, __amd64__ or __x64_86__. + * + * - Take care and use size_t when you have to, esp. when passing a pointer + * to a size_t as a parameter. + * + * - Be wary of type promotion to (signed) integer. For example the + * following will cause u8 to be promoted to int in the shift, and then + * sign extended in the assignment 64-bit: + * @code + * uint8_t u8 = 0xfe; + * uint64_t u64 = u8 << 24; + * // u64 == 0xfffffffffe000000 + * @endcode + * + * + * @subsection sec_vbox_guideline_compulsory_cppmain C++ guidelines for Main + * + * Main is currently (2009) full of hard-to-maintain code that uses complicated + * templates. The new mid-term goal for Main is to have less custom templates + * instead of more for the following reasons: + * + * - Template code is harder to read and understand. Custom templates create + * territories which only the code writer understands. + * + * - Errors in using templates create terrible C++ compiler messages. + * + * - Template code is really hard to look at in a debugger. + * + * - Templates slow down the compiler a lot. + * + * In particular, the following bits should be considered deprecated and should + * NOT be used in new code: + * + * - everything in include/iprt/cpputils.h (auto_ref_ptr, exception_trap_base, + * char_auto_ptr and friends) + * + * Generally, in many cases, a simple class with a proper destructor can achieve + * the same effect as a 1,000-line template include file, and the code is + * much more accessible that way. + * + * Using standard STL templates like std::list, std::vector and std::map is OK. + * Exceptions are: + * + * - Guest Additions because we don't want to link against libstdc++ there. + * + * - std::string should not be used because we have iprt::MiniString and + * com::Utf8Str which can convert efficiently with COM's UTF-16 strings. + * + * - std::auto_ptr<> in general; that part of the C++ standard is just broken. + * Write a destructor that calls delete. + * + * + * @subsection sec_vbox_guideline_compulsory_cppqtgui C++ guidelines for the Qt GUI + * + * The Qt GUI is currently (2010) on its way to become more compatible to the + * rest of VirtualBox coding style wise. From now on, all the coding style + * rules described in this file are also mandatory for the Qt GUI. Additionally + * the following rules should be respected: + * + * - GUI classes which correspond to GUI tasks should be prefixed by UI (no VBox anymore) + * + * - Classes which extents some of the Qt classes should be prefix by QI + * + * - General task classes should be prefixed by C + * + * - Slots are prefixed by slt -> sltName + * + * - Signals are prefixed by sig -> sigName + * + * - Use Qt classes for lists, strings and so on, the use of STL classes should + * be avoided + * + * - All files like .cpp, .h, .ui, which belong together are located in the + * same directory and named the same + * + * + * @section sec_vbox_guideline_optional Optional + * + * First part is the actual coding style and all the prefixes. The second part + * is a bunch of good advice. + * + * + * @subsection sec_vbox_guideline_optional_layout The code layout + * + * - Max line length is 130 chars. Exceptions are table-like + * code/initializers and Log*() statements (don't waste unnecessary + * vertical space on debug logging). + * + * - Comments should try stay within the usual 80 columns. + * + * - Curly brackets are not indented. Example: + * @code + * if (true) + * { + * Something1(); + * Something2(); + * } + * else + * { + * SomethingElse1(). + * SomethingElse2(). + * } + * @endcode + * + * - Space before the parentheses when it comes after a C keyword. + * + * - No space between argument and parentheses. Exception for complex + * expression. Example: + * @code + * if (PATMR3IsPatchGCAddr(pVM, GCPtr)) + * @endcode + * + * - The else of an if is always the first statement on a line. (No curly + * stuff before it!) + * + * - else and if go on the same line if no { compound statement } + * follows the if. Example: + * @code + * if (fFlags & MYFLAGS_1) + * fFlags &= ~MYFLAGS_10; + * else if (fFlags & MYFLAGS_2) + * { + * fFlags &= ~MYFLAGS_MASK; + * fFlags |= MYFLAGS_5; + * } + * else if (fFlags & MYFLAGS_3) + * @endcode + * + * + * - Slightly complex boolean expressions are split into multiple lines, + * putting the operators first on the line and indenting it all according + * to the nesting of the expression. The purpose is to make it as easy as + * possible to read. Example: + * @code + * if ( RT_SUCCESS(rc) + * || (fFlags & SOME_FLAG)) + * @endcode + * + * - When 'if' or 'while' statements gets long, the closing parentheses + * goes right below the opening parentheses. This may be applied to + * sub-expression. Example: + * @code + * if ( RT_SUCCESS(rc) + * || ( fSomeStuff + * && fSomeOtherStuff + * && fEvenMoreStuff + * ) + * || SomePredicateFunction() + * ) + * { + * ... + * } + * @endcode + * + * - The case is indented from the switch (to avoid having the braces for + * the 'case' at the same level as the 'switch' statement). + * + * - If a case needs curly brackets they contain the entire case, are not + * indented from the case, and the break or return is placed inside them. + * Example: + * @code + * switch (pCur->eType) + * { + * case PGMMAPPINGTYPE_PAGETABLES: + * { + * unsigned iPDE = pCur->GCPtr >> PGDIR_SHIFT; + * unsigned iPT = (pCur->GCPtrEnd - pCur->GCPtr) >> PGDIR_SHIFT; + * while (iPT-- > 0) + * if (pPD->a[iPDE + iPT].n.u1Present) + * return VERR_HYPERVISOR_CONFLICT; + * break; + * } + * } + * @endcode + * + * - In a do while construction, the while is on the same line as the + * closing "}" if any are used. + * Example: + * @code + * do + * { + * stuff; + * i--; + * } while (i > 0); + * @endcode + * + * - Comments are in C style. C++ style comments are used for temporary + * disabling a few lines of code. + * + * - No unnecessary parentheses in expressions (just don't over do this + * so that gcc / msc starts bitching). Find a correct C/C++ operator + * precedence table if needed. + * + * - 'for (;;)' is preferred over 'while (true)' and 'while (1)'. + * + * - Parameters are indented to the start parentheses when breaking up + * function calls, declarations or prototypes. (This is in line with + * how 'if', 'for' and 'while' statements are done as well.) Example: + * @code + * RTPROCESS hProcess; + * int rc = RTProcCreateEx(papszArgs[0], + * papszArgs, + * RTENV_DEFAULT, + * fFlags, + * NULL, // phStdIn + * NULL, // phStdOut + * NULL, // phStdErr + * NULL, // pszAsUser + * NULL, // pszPassword + * &hProcess); + * @endcode + * + * - That Dijkstra is dead is no excuse for using gotos. + * + * + * + * @subsection sec_vbox_guideline_optional_prefix Variable / Member Prefixes + * + * - The 'g_' (or 'g') prefix means a global variable, either on file or module level. + * + * - The 's_' (or 's') prefix means a static variable inside a function or class. + * + * - The 'm_' (or 'm') prefix means a class data member. + * + * In new code in Main, use "m_" (and common sense). As an exception, + * in Main, if a class encapsulates its member variables in an anonymous + * structure which is declared in the class, but defined only in the + * implementation (like this: 'class X { struct Data; Data *m; }'), then + * the pointer to that struct is called 'm' itself and its members then + * need no prefix, because the members are accessed with 'm->member' + * already which is clear enough. + * + * - The 'a_' prefix means a parameter (argument) variable. This is + * sometimes written 'a' in parts of the source code that does not use + * the array prefix. + * + * - The 'p' prefix means pointer. For instance 'pVM' is pointer to VM. + * + * - The 'r' prefix means that something is passed by reference. + * + * - The 'k' prefix means that something is a constant. For instance + * 'enum { kStuff };'. This is usually not used in combination with + * 'p', 'r' or any such thing, it's main main use is to make enums + * easily identifiable. + * + * - The 'a' prefix means array. For instance 'aPages' could be read as + * array of pages. + * + * - The 'c' prefix means count. For instance 'cbBlock' could be read, + * count of bytes in block. + * + * - The 'off' prefix means offset. + * + * - The 'i' or 'idx' prefixes usually means index. Although the 'i' one + * can sometimes just mean signed integer. + * + * - The 'i[1-9]+' prefix means a fixed bit size variable. Frequently + * used with the int[1-9]+_t types. [type] + * + * - The 'e' (or 'enm') prefix means enum. + * + * - The 'u' prefix usually means unsigned integer. Exceptions follows. + * + * - The 'u[1-9]+' prefix means a fixed bit size variable. Frequently + * used with the uint[1-9]+_t types and with bitfields. [type] + * + * - The 'b' prefix means byte or bytes. [type] + * + * - The 'f' prefix means flags. Flags are unsigned integers of some kind + * or booleans. + * + * - TODO: need prefix for real float. [type] + * + * - The 'rd' prefix means real double and is used for 'double' variables. + * [type] + * + * - The 'lrd' prefix means long real double and is used for 'long double' + * variables. [type] + * + * - The 'ch' prefix means a char, the (signed) char type. [type] + * + * - The 'wc' prefix means a wide/windows char, the RTUTF16 type. [type] + * + * - The 'uc' prefix means a Unicode Code point, the RTUNICP type. [type] + * + * - The 'uch' prefix means unsigned char. It's rarely used. [type] + * + * - The 'sz' prefix means zero terminated character string (array of + * chars). (UTF-8) + * + * - The 'wsz' prefix means zero terminated wide/windows character string + * (array of RTUTF16). + * + * - The 'usz' prefix means zero terminated Unicode string (array of + * RTUNICP). + * + * - The 'str' prefix means C++ string; either a std::string or, in Main, + * a Utf8Str or, in Qt, a QString. When used with 'p', 'r', 'a' or 'c' + * the first letter should be capitalized. + * + * - The 'bstr' prefix, in Main, means a UTF-16 Bstr. When used with 'p', + * 'r', 'a' or 'c' the first letter should be capitalized. + * + * - The 'pfn' prefix means pointer to function. Common usage is 'pfnCallback' + * and such like. + * + * - The 'psz' prefix is a combination of 'p' and 'sz' and thus means + * pointer to a zero terminated character string. (UTF-8) + * + * - The 'pcsz' prefix is used to indicate constant string pointers in + * parts of the code. Most code uses 'psz' for const and non-const + * string pointers. + * + * - The 'l' prefix means (signed) long. We try avoid using this, + * expecially with the 'LONG' types in Main as these are not 'long' on + * 64-bit non-Windows platforms and can cause confusion. Alternatives: + * 'i' or 'i32'. [type] + * + * - The 'ul' prefix means unsigned long. We try avoid using this, + * expecially with the 'ULONG' types in Main as these are not 'unsigned + * long' on 64-bit non-Windows platforms and can cause confusion. + * Alternatives: 'u' or 'u32'. [type] + * + * + * @subsection sec_vbox_guideline_optional_misc Misc / Advice / Stuff + * + * - When writing code think as the reader. + * + * - When writing code think as the compiler. (2) + * + * - When reading code think as if it's full of bugs - find them and fix them. + * + * - Pointer within range tests like: + * @code + * if ((uintptr_t)pv >= (uintptr_t)pvBase && (uintptr_t)pv < (uintptr_t)pvBase + cbRange) + * @endcode + * Can also be written as (assuming cbRange unsigned): + * @code + * if ((uintptr_t)pv - (uintptr_t)pvBase < cbRange) + * @endcode + * Which is shorter and potentially faster. (1) + * + * - Avoid unnecessary casting. All pointers automatically cast down to + * void *, at least for non class instance pointers. + * + * - It's very very bad practise to write a function larger than a + * screen full (1024x768) without any comprehensibility and explaining + * comments. + * + * - More to come.... + * + * + * (1) Important, be very careful with the casting. In particular, note that + * a compiler might treat pointers as signed (IIRC). + * + * (2) "A really advanced hacker comes to understand the true inner workings of + * the machine - he sees through the language he's working in and glimpses + * the secret functioning of the binary code - becomes a Ba'al Shem of + * sorts." (Neal Stephenson "Snow Crash") + * + * + * + * @section sec_vbox_guideline_warnings Compiler Warnings + * + * The code should when possible compile on all platforms and compilers without any + * warnings. That's a nice idea, however, if it means making the code harder to read, + * less portable, unreliable or similar, the warning should not be fixed. + * + * Some of the warnings can seem kind of innocent at first glance. So, let's take the + * most common ones and explain them. + * + * + * @subsection sec_vbox_guideline_warnings_signed_unsigned_compare Signed / Unsigned Compare + * + * GCC says: "warning: comparison between signed and unsigned integer expressions" + * MSC says: "warning C4018: '<|<=|==|>=|>' : signed/unsigned mismatch" + * + * The following example will not output what you expect: +@code +#include <stdio.h> +int main() +{ + signed long a = -1; + unsigned long b = 2294967295; + if (a < b) + printf("%ld < %lu: true\n", a, b); + else + printf("%ld < %lu: false\n", a, b); + return 0; +} +@endcode + * If I understood it correctly, the compiler will convert a to an + * unsigned long before doing the compare. + * + * + * + * @section sec_vbox_guideline_svn Subversion Commit Rules + * + * + * Before checking in: + * + * - Check Tinderbox and make sure the tree is green across all platforms. If it's + * red on a platform, don't check in. If you want, warn in the \#vbox channel and + * help make the responsible person fix it. + * NEVER CHECK IN TO A BROKEN BUILD. + * + * - When checking in keep in mind that a commit is atomic and that the Tinderbox and + * developers are constantly checking out the tree. Therefore do not split up the + * commit unless it's into 100% independent parts. If you need to split it up in order + * to have sensible commit comments, make the sub-commits as rapid as possible. + * + * - If you make a user visible change, such as fixing a reported bug, + * make sure you add an entry to doc/manual/user_ChangeLogImpl.xml. + * + * - If you are adding files make sure set the right attributes. + * svn-ps.sh/cmd was created for this purpose, please make use of it. + * + * + * After checking in: + * + * - After checking-in, you watch Tinderbox until your check-ins clear. You do not + * go home. You do not sleep. You do not log out or experiment with drugs. You do + * not become unavailable. If you break the tree, add a comment saying that you're + * fixing it. If you can't fix it and need help, ask in the \#innotek channel or back + * out the change. + * + * (Inspired by mozilla tree rules.) + */ + |