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7a934d0bef
Replace traditional `#ifndef`/`#define`/`#endif` include guards with
`#pragma` once.
`#pragma once` is a widely supported preprocessor directive that
prevents header files from being included multiple times. It is
supported by all toolchains used to build edk2: GCC, Clang/LLVM, and
MSVC.
Compared to macro-based include guards, `#pragma once`:
- Eliminates the risk of macro name collisions or copy/paste errors
where two headers inadvertently use the same guard macro.
- Eliminate inconsistency in the way include guard macros are named
(e.g., some files use `__FILE_H__`, others use `FILE_H_`, etc.).
- Reduces boilerplate (three lines replaced by one).
- Avoids polluting the macro namespace with guard symbols.
- Can improve build times as the preprocessor can skip re-opening the
file entirely, rather than re-reading it to find the matching
`#endif` ("multiple-include optimization").
- Note that some compilers may already optimize traditional include
guards, by recognzining the idiomatic pattern.
This change is made acknowledging that overall portability of the
code will technically be reduced, as `#pragma once` is not part of the
C/C++ standards.
However, this is considered acceptable given:
1. edk2 already defines a subset of supported compilers in
BaseTools/Conf/tools_def.template, all of which have supported
`#pragma once` for over two decades.
2. There have been concerns raised to the project about inconsistent
include guard naming and potential macro collisions.
Approximate compiler support dates:
- MSVC: Supported since Visual C++ 4.2 (1996)
- GCC: Supported since 3.4 (2004)
(http://gnu.ist.utl.pt/software/gcc/gcc-3.4/changes.html)
- Clang (LLVM based): Since initial release in 2007
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
38 lines
1.2 KiB
C
38 lines
1.2 KiB
C
/** @file
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The variable data structures are related to EDK II-specific implementation of UEFI variables.
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VariableFormat.h defines variable data headers and variable storage region headers.
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Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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#pragma once
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typedef struct {
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VARIABLE_HEADER *CurrPtr;
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VARIABLE_HEADER *EndPtr;
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VARIABLE_HEADER *StartPtr;
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} VARIABLE_POINTER_TRACK;
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#define VARIABLE_INDEX_TABLE_VOLUME 122
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#define EFI_VARIABLE_INDEX_TABLE_GUID \
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{ 0x8cfdb8c8, 0xd6b2, 0x40f3, { 0x8e, 0x97, 0x02, 0x30, 0x7c, 0xc9, 0x8b, 0x7c } }
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extern EFI_GUID gEfiVariableIndexTableGuid;
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///
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/// Use this data structure to store variable-related info, which can decrease
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/// the cost of access to NV.
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///
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typedef struct {
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UINT16 Length;
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UINT16 GoneThrough;
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VARIABLE_HEADER *EndPtr;
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VARIABLE_HEADER *StartPtr;
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///
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/// This field is used to store the distance of two neighbouring VAR_ADDED type variables.
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/// The meaning of the field is implement-dependent.
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UINT16 Index[VARIABLE_INDEX_TABLE_VOLUME];
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} VARIABLE_INDEX_TABLE;
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