|
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>
|
|
For Arm-based platforms, define and implement an interface for Server
Base Boot Requirements (SBBR) compliance checks. The library is
responsible for validating that all mandatory ACPI tables are installed
on the platform.
Internally, the library maintains a data structure which tracks
instance counts for ACPI tables which are labeled as 'mandatory' in any
SBBR specification version. The provided interface allows:
- resetting all instance counts to 0
- incremementing the instance count for a table with a given signature
- validating the instance counts against the requirements in SBBR
The ACPI table requirements for each SBBR spec version are represented
internally as a list of table signatures.
Every missing mandatory table (for the input SBBR version) is reported
to the user as a separate error. If all requirements are met, an info
message is displayed.
Reference(s):
- Arm Server Base Boot Requirements 1.2, September 2019
- Arm Server Base Boot Requirements 1.1, May 2018
- Arm Server Base Boot Requirements 1.0, March 2016
Signed-off-by: Krzysztof Koch <krzysztof.koch@arm.com>
Reviewed-by: Sami Mujawar <Sami.Mujawar@arm.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>
|
