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py: Fix compiling and decoding of args at large arg positions. There were two issues with the existing code: 1. "1 << i" is computed as a 32-bit number so would overflow when executed on 64-bit machines (when mp_uint_t is 64-bit). This meant that args beyond 32 positions would not be handled correctly. 2. star_args must fit as a positive small int so that it is encoded correctly in the emitted code. MP_SMALL_INT_BITS is too big because it overflows a small int by 1 bit. MP_SMALL_INT_BITS - 1 does not work because it produces a signed small int which is then sign extended when extracted (even by mp_obj_get_int_truncated), and this sign extension means that any position arg after *args is also treated as a star-arg. So the maximum bit position is MP_SMALL_INT_BITS - 2. This means that MP_OBJ_SMALL_INT_VALUE() can be used instead of mp_obj_get_int_truncated() to get the value of star_args. These issues are fixed by this commit, and a test added. Signed-off-by: Damien George <damien@micropython.org> 2022-03-31 15:00:58 +02:00			`33`
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