test_ctypes: test_shorts() of ctypes.test.test_bitfields.C_Test is failing with:

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test_shorts (ctypes.test.test_bitfields.C_Test) ... /home/vstinner/python/main/Modules/_ctypes/cfield.c:554:5: runtime error: shift exponent 18446744073709551614 is too large for 16-bit type 'short'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/vstinner/python/main/Modules/_ctypes/cfield.c:554:5 in 
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It's a test on the "h" format code:
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#define LOW_BIT(x)  ((x) & 0xFFFF)
#define NUM_BITS(x) ((x) >> 16)

#define GET_BITFIELD(v, size)                                           \
    if (NUM_BITS(size)) {                                               \
        v <<= (sizeof(v)*8 - LOW_BIT(size) - NUM_BITS(size));           \
        v >>= (sizeof(v)*8 - NUM_BITS(size));                           \

static PyObject *
h_get(void *ptr, Py_ssize_t size)
{
    short val;
    memcpy(&val, ptr, sizeof(val));
    GET_BITFIELD(val, size); // <==== HERE
    return PyLong_FromLong((long)val);
}

static struct fielddesc formattable[] = {
    ...
    { 'h', h_set, h_get, NULL, h_set_sw, h_get_sw},
    ...
};
----