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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>
94 lines
3 KiB
C
94 lines
3 KiB
C
/** @file
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Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
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Copyright (c) 2013 - 2021, Arm Limited. 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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CHAR8 *FileName;
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UINTN Mode;
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UINTN NameLength;
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} SEMIHOST_FILE_OPEN_BLOCK;
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typedef struct {
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UINTN Handle;
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VOID *Buffer;
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UINTN Length;
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} SEMIHOST_FILE_READ_WRITE_BLOCK;
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typedef struct {
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UINTN Handle;
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UINTN Location;
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} SEMIHOST_FILE_SEEK_BLOCK;
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typedef struct {
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VOID *Buffer;
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UINTN Identifier;
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UINTN Length;
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} SEMIHOST_FILE_TMPNAME_BLOCK;
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typedef struct {
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CHAR8 *FileName;
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UINTN NameLength;
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} SEMIHOST_FILE_REMOVE_BLOCK;
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typedef struct {
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CHAR8 *FileName;
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UINTN FileNameLength;
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CHAR8 *NewFileName;
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UINTN NewFileNameLength;
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} SEMIHOST_FILE_RENAME_BLOCK;
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typedef struct {
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CHAR8 *CommandLine;
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UINTN CommandLength;
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} SEMIHOST_SYSTEM_BLOCK;
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#if defined (__GNUC__)
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#define SEMIHOST_SUPPORTED TRUE
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UINT32
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GccSemihostCall (
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IN UINT32 Operation,
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IN UINTN SystemBlockAddress
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); // __attribute__ ((interrupt ("SVC")));
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#define SEMIHOST_SYS_OPEN(OpenBlock) GccSemihostCall(0x01, (UINTN)(OpenBlock))
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#define SEMIHOST_SYS_CLOSE(Handle) GccSemihostCall(0x02, (UINTN)(Handle))
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#define SEMIHOST_SYS_WRITE0(String) GccSemihostCall(0x04, (UINTN)(String))
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#define SEMIHOST_SYS_WRITEC(Character) GccSemihostCall(0x03, (UINTN)(Character))
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#define SEMIHOST_SYS_WRITE(WriteBlock) GccSemihostCall(0x05, (UINTN)(WriteBlock))
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#define SEMIHOST_SYS_READ(ReadBlock) GccSemihostCall(0x06, (UINTN)(ReadBlock))
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#define SEMIHOST_SYS_READC() GccSemihostCall(0x07, (UINTN)(0))
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#define SEMIHOST_SYS_SEEK(SeekBlock) GccSemihostCall(0x0A, (UINTN)(SeekBlock))
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#define SEMIHOST_SYS_FLEN(Handle) GccSemihostCall(0x0C, (UINTN)(Handle))
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#define SEMIHOST_SYS_TMPNAME(TmpNameBlock) GccSemihostCall(0x0D, (UINTN)(TmpNameBlock))
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#define SEMIHOST_SYS_REMOVE(RemoveBlock) GccSemihostCall(0x0E, (UINTN)(RemoveBlock))
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#define SEMIHOST_SYS_RENAME(RenameBlock) GccSemihostCall(0x0F, (UINTN)(RenameBlock))
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#define SEMIHOST_SYS_SYSTEM(SystemBlock) GccSemihostCall(0x12, (UINTN)(SystemBlock))
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#else // __GNUC__
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#define SEMIHOST_SUPPORTED FALSE
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#define SEMIHOST_SYS_OPEN(OpenBlock) (-1)
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#define SEMIHOST_SYS_CLOSE(Handle) (-1)
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#define SEMIHOST_SYS_WRITE0(String)
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#define SEMIHOST_SYS_WRITEC(Character)
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#define SEMIHOST_SYS_WRITE(WriteBlock) (0)
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#define SEMIHOST_SYS_READ(ReadBlock) ((ReadBlock)->Length)
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#define SEMIHOST_SYS_READC() ('x')
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#define SEMIHOST_SYS_SEEK(SeekBlock) (-1)
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#define SEMIHOST_SYS_FLEN(Handle) (-1)
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#define SEMIHOST_SYS_TMPNAME(TmpNameBlock) (-1)
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#define SEMIHOST_SYS_REMOVE(RemoveBlock) (-1)
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#define SEMIHOST_SYS_RENAME(RenameBlock) (-1)
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#define SEMIHOST_SYS_SYSTEM(SystemBlock) (-1)
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#endif // __GNUC__
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