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Very few functions are asynchronous-safe. If a function performs any other operations, it is probably not asynchronous-safe.
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*free-standingfreestanding environment* \[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\] An environment in which C program execution may take place without any benefit of an operating system. Program startup might occur at some function other than {{main()}}, complex types might not be implemented, and only certain minimal library facilities are guaranteed to be available. |
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