MdePkg: 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

MdePkg: Create Stack Check Null Libs

2024-09-13T03:58:46+00:00

Add Null libs for Stack Check and Stack Check Failure Hook Lib that allow a platform to opt out of stack checks and the stack check failure hook lib. StackCheckLib allows implementation (or in this case null implementation) of stack checks on binaries. There is a Host Application specific version of this null lib because MSVC host applications must not be linked against our lib (so the file here is a no-op but that doesn't cause the build system to fail the build for not building a file for MSVC) as it links against the MSVC C runtime lib that provides the stack cookie definitions. GCC host applications do not link against such a C runtime lib and must be linked against our version. StackCheckFailureHookLib lets a platform do custom functionality when a stack check failure occurs (such as log it to a platform defined mechanism). The null lib simply returns. Signed-off-by: Oliver Smith-Denny

Tianocore/edk2.git/MdePkg/Include/Library/StackCheckFailureHookLib.h, branch master

MdePkg: Replace include guards with #pragma once

MdePkg: Create Stack Check Null Libs