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__attribute__((nothrow)) function attribute

This attribute asserts that a call to a function never results in a C++ exception being sent from the callee to the caller.

The Arm® library headers automatically add this qualifier to declarations of C functions that, according to the ISO C Standard, can never throw an exception. However, there are some restrictions on the unwinding tables produced for the C library functions that might throw an exception in a C++ context, for example, bsearch and qsort.

If the compiler knows that a function can never throw an exception, it might be able to generate smaller exception-handling tables for callers of that function.