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/* $Id: Docs-CodingGuidelines.cpp $ */
/** @file
* VMM - Coding Guidelines.
*/
/*
* Copyright (C) 2006-2020 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_vmm_guideline VMM Coding Guidelines
*
* The guidelines extends the VBox coding guidelines (@ref pg_vbox_guideline)
* and consists of a compulsory part and an optional part. It is very important
* that the rules of the compulsory part is followed. That will prevent obvious
* bugs, and it will ease porting the code to 32/64 and 64/32 bits setups.
*
*
*
* @section sec_vmm_guideline_compulsory Compulsory
*
* It is of vital importance is to distinguish between addresses - both virtual
* and physical - applying to Guest Context and Host Context. To assist the
* coder in this, a set of types and macros have been created. Another vital
* thing is that structures shared between the two contexts ends up with the
* same size and member offsets in both places. There are types and macros
* for that too.
*
*
* The rules:
*
* - When declaring pointers in shared structures use the RCPTRTYPE(),
* R0PTRTYPE() and R3PTRTYPE() macros.
*
* - Use RTGCPTR and RTHCPTR when dealing with the other context in
* none shared structures, parameter lists, stack variables and such.
*
* - Following the above rules, pointers will in a context other than the
* one a pointer was defined for, appear as unsigned integers.
*
* - It is NOT permitted to subject a pointer from the other context to pointer
* types of the current context by direct cast or by definition.
*
* - When doing pointer arithmetic cast using uintptr_t, intptr_t or char *.
* Never cast a pointer to anything else for this purpose, that will not
* work everywhere! (1)
*
* - Physical addresses are also specific to their context. Use RTGCPHYS
* and RTHCPHYS when dealing when them. Both types are unsigned integers.
*
* - Integers in shared structures should be using a RT integer type or
* any of the [u]int[0-9]+_t types. (2)
*
* - If code is shared between the contexts, GCTYPE() can be used to declare
* things differently. If GCTYPE() usage is extensive, don't share the code.
*
* - The context is part of all public symbols which are specific to a single
* context.
*
*
* (1) Talking about porting between 32-bit and 64-bit architectures and even
* between 64-bit platforms. On 64-bit linux int is 32-bit, long is 64-bit.
* However on 64-bit windows both int and long are 32-bit - there is no
* standard 64 bit type (_int64 is not a standard type, it's an stupid
* extension).
*
* (2) The VBox integer types are RTINT, RTUINT, RTGCINT, RTGCUINT,
* RTGCINTPTR, RTGCUINTPTR, RTHCINT, RTHCUINT, RTHCINTPTR and
* RTHCUINTPTR.
*
*
*
* @section sec_vmm_guideline_optional Optional
*
* There are the general VBox guidelines, see @ref sec_vbox_guideline_optional.
* In addition to these for the following rules applies to the VMM:
*
* - Prefixes GCPtr and HCPtr are preferred over suffixes HC and GC of
* pointers.
*
* - Prefixes GCPhys and HCPhys are generally used for physical addresses,
* types RTGCPHYS and RTHCPHYS respectively.
*
*/
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