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*asynchronous-safe* \[[GNU Pth|AA. C References#GNU Pth]\]
A function is "async-safe" if it can called safely and without side effects from within a signal handler context. That is, it must be able to be interrupted at any point and run linearly out of sequence without causing an inconsistent state. Very few functions are asynchronous-safe. The list below lists async-safe operations. If a function does anything not on the list, it is probably not asynchronous-safe: |
- call the
signal()function to reinstall a signal handler - unconditionally modify a
volatile sig_atomic_tvariable (as modification to this type is atomic) - call the
_Exit()function to immediately terminate program execution - use a function from the extremely small subset of library functions listed in your
signal()documentation as async-safe
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*free-standing environment* \[[Banahan 03|AA. C References#Banahan 03]\]
An environment without the C standard libraries. Common for stand-alone programs, such as operating systems or firmware. |
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*hosted environment* \[[Banahan 03|AA. C References#Banahan 03]\]
An environment that supplies the C standard libraries. |
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*verification* \[[IEC 61508-4|AA. C References#IEC 61508-4]\]
Confirmation by examination and provision of objective evidence that the requirements have been fulfilled. |