Tianocore/edk2.git/MdeModulePkg/Include/Guid/MmCommBuffer.h, branch master

MdeModulePkg: Replace include guards with #pragma once

2026-02-23T21:01:28+00:00

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

MdeModulePkg: Update MM buffer structs alignment

2025-04-14T08:44:05+00:00

In general, for all HOB related content, the HOB structures must be designed so that natural alignment across all execution modes and byte-packed alignment are the same. Ensure ReturnStatus is aligned on 64 bit to achieve the same. Signed-off-by: Dhaval Sharma

MdeModulePkg: Add MM Communication Buffer definition

2024-08-28T15:25:27+00:00

The MM communicate buffer facilitates data sharing between non-MM and MM code. The MM IPL code allocates a "fixed" runtime type memory as the MM communication buffer, and communicates its address and size to MM Core via MmCommBuffer GUIDed HOB. Here, "fixed" implies that the buffer's location remains constant throughout the boot process. Data is exchanged between the MM Communication PPI/Protocol and a software MMI handler using this fixed MM communication buffer. Signed-off-by: Hongbin1 Zhang Co-authored-by: Jiaxin Wu Cc: Liming Gao Co-authored-by: Ray Ni Cc: Star Zeng Cc: Wei6 Xu Cc: Dun Tan Cc: Yuanhao Xie