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Describes implementation-defined aspects of the ARM C compiler and C library relating to qualifiers, as required by the ISO C standard.
An object that has a volatile-qualified type is accessed as a word, halfword, or byte as determined by its size and alignment. For volatile objects larger than a word, the order of accesses to the parts of the object is undefined. Updates to volatile bitfields generally require a read-modify-write. Accesses to aligned word, halfword and byte types are atomic. Other volatile accesses are not necessarily atomic.
Otherwise, reads and writes to volatile qualified objects occur as directly implied by the source code, in the order implied by the source code.