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52 lines
2.1 KiB
Plaintext
52 lines
2.1 KiB
Plaintext
/**
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@defgroup sys_cxx_ctor_guards C++ constructor guards for static instances
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@ingroup cpp
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@brief C++ constructor guards for thread-safe initialization of static
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instances
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@warning This implementation is likely only compatible with `g++`
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# Introduction
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The libstd++ ABI requires implementations of the following functions:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.c}
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int __cxa_guard_acquire(__guard *g);
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void __cxa_guard_release(__guard *g);
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void __cxa_guard_abort(__guard *g);
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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These functions are not intended to be ever used by the programmer, instead
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the C++ compiler will emit code calling them if statically allocated class
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instances are used. In a multi-threaded environment special care needs to be
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taken to prevent race conditions while initializing and using such instances.
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This modules provides them.
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# Usage
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This module is intended to be used by platforms that want to provide C++
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support, but the used standard C++ library does not provide these guards. In
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this case, adding this module will do the trick. The programmer / user should
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never interact with any of the functions.
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Note that on some platforms the type `__guard` is defined differently from the
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"generic" definition, most notably ARM. For those platforms a header named
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`cxx_ctor_guards_arch.h` needs to be created containing the correct `typedef`
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and the preprocessor macro `CXX_CTOR_GUARDS_CUSTOM_TYPE` needs to be defined.
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# Implementation
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This implementation provides the C++ ctor guards as defined by the libstd++ ABI
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used in g++. It will likely not be compatible with other implementations of
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libstd++.
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The libstd++ ABI expects the functions to be implemented as C functions. Most
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implementations will put the code into C++ files and wrap everything into an
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`extern "C" {...}`. This implementation will just use a plain C file for less
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boilerplate.
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The implementation intentionally makes only use of a single byte of the
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`__guard` type. This should result in the implementation being usable on any
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platform, regardless of the actual size of `__guard`.
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*/
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