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The C++ Standard, [support.runtime], paragraph 10 [ISO/IEC 14882-2014], states the following:
The common subset of the C and C++ languages consists of all declarations, definitions, and expressions that may appear in a well-formed C++ program and also in a conforming C program. A POF (“plain old function”) is a function that uses only features from this common subset, and that does not directly or indirectly use any function that is not a POF, except that it may use plain lock-free atomic operations.
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A plain lock-free atomic operation is an invocation of a function f from Clause 29, such that f is not a member function, and either f is the function atomic_is_lock_free, or for every atomic argument
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A passed to f, atomic_is_lock_free(A) yields true. All signal handlers shall have C linkage. The behavior of any function other than a POF used as a signal handler in a C++ program is implementation-defined.228
Footnote 228 states the following:
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