The implementation clears the context / state data from memory when it
is finished with it. Prior to this commit, however, it was actually
only clearing the first 4 bytes on x86 or 8 bytes on x86_64.
clang warns:
warning: argument to 'sizeof' in 'memset' call is the same
expression as the destination; did you mean to dereference it?
[-Wsizeof-pointer-memaccess]