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>
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|---|---|---|
| .. | ||
| BaseTraceHubDebugSysTLib.c | ||
| BaseTraceHubDebugSysTLib.inf | ||
| DxeSmmTraceHubDebugSysTLib.c | ||
| DxeSmmTraceHubDebugSysTLib.inf | ||
| InternalTraceHubApi.c | ||
| InternalTraceHubApi.h | ||
| InternalTraceHubApiCommon.c | ||
| InternalTraceHubApiCommon.h | ||
| PeiTraceHubDebugSysTLib.c | ||
| PeiTraceHubDebugSysTLib.inf | ||
| Readme.md | ||
Introduction of TrcaceHubDebugSysTLib
TrcaceHubDebugSysTLib library is a top level library for dumping Trace Hub messages. It provides Trace Hub related APIs to dump Trace Hub message via MIPI SYS-T submodule. User need to properly configure following Trace Hub related PCDs and HOB. (See MdeModulePkg.dec to get detailed definition for PCDs below)
- PcdTraceHubDebugLevel
- PcdEnableTraceHubDebugMsg
- PcdTraceHubDebugMmioAddress (See TraceHubDebugInfoHob.h to get detailed definition for HOB below)
- gTraceHubDebugInfoHobGuid
BaseTraceHubDebugSysTLib.inf
System prints Trace Hub message in SEC/PEI/DXE/SMM based on fixed PCDs. Only support single Trace Hub debug instance.
PeiTraceHubDebugSysTLib.inf
System prints Trace Hub message in PEI based on fixed PCDs and HOB. System applies Trace Hub HOB once it detect gTraceHubDebugInfoHobGuid HOB. Trace Hub PCDs will be applied if no HOB exist.
DxeSmmTraceHubDebugSysTLib.inf
System prints Trace Hub message in DXE/SMM based on fixed PCDs and HOB. Trace Hub PCDs will be applied if no HOB exist.
Note
Trace Hub debug library not support DXE_RUNTIME_DRIVER type of module currently.