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GCC 17 (upcoming release) is updating the type of
__stack_chk_guard from a void * to a uintptr_t.
This is only a type change, not a size change. However,
it does cause the GCC 17 build to fail because of the
type mismatch.
uintptr_t is defined as unsigned long, which is not
a type edk2 defines. It has the same size as UINTN
on a given system, but on 64 bit systems we have the
same type issue because UINTN is defined as unsigned long long,
not unsigned long.
To work around this and avoid defining a new type in edk2,
use the compiler built in __UINTPTR_TYPE__ which is the
underlying definition in GCC.
This is a backwards compatible change with previous versions
of GCC and CLANGDWARF but also fixes the upcoming definition
change for GCC 17.
Signed-off-by: Oliver Smith-Denny <osde@microsoft.com>
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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>
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StackCheckLib defines the interface between a compiler
and the stack checking code. It is being converted from
a NULL library class to an actual library class to make
it easier to use for a platform and be easier to define
the expected interface with a compiler, so if there is
a compiler change it can be tracked and caught.
Signed-off-by: Oliver Smith-Denny <osde@microsoft.com>
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