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__attribute__((const)) function attribute

The const function attribute specifies that a function examines only its arguments, and has no effect except for the return value. That is, the function does not read or modify any global memory.

If a function is known to operate only on its arguments then it can be subject to common sub-expression elimination and loop optimizations.

This is a much stricter class than __attribute__((pure)) because functions are not permitted to read global memory.

Note: This function attribute is a GNU compiler extension that the ARM compiler supports. It has the keyword equivalent __pure.