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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>
29 lines
997 B
C
29 lines
997 B
C
/** @file
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Provides a library function that can be customized to set the platform to boot
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from USB on the next boot. This allows the test framework to reboot back to
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USB. Since boot managers are not all the same creating a lib to support
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platform customization will make porting to new code base/platform easier.
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Copyright (c) Microsoft Corporation.<BR>
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Copyright (c) 2019 - 2020, 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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/**
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Set the boot manager to boot from a specific device on the next boot. This
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should be set only for the next boot and shouldn't require any manual clean up
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@retval EFI_SUCCESS Boot device for next boot was set.
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@retval EFI_UNSUPPORTED Setting the boot device for the next boot is not
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supportted.
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@retval Other Boot device for next boot can not be set.
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**/
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EFI_STATUS
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EFIAPI
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SetBootNextDevice (
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VOID
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);
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