Running with UBSan throws runtime error regarding bitshift

[Daniel Gröber (dxld)]

When running theft with ubsan enabled (-fsanitize=undefined) I get the following error:

.src/theft_random.c:79:21: runtime error: shift exponent 64 is too large for 64-bit type 'long unsigned int'

At the mentioned source location we have:

    uint8_t shift = 0;
[...]
        uint8_t take = 64 - shift;
[...]
        t->prng.buf >>= take;

According to the C standard shifting by more than the types size is undefined behaviour:

The behavior is undefined in the following circumstances:
[...]

• An expression is shifted by a negative number or by an amount greater than or equal
  to the width of the promoted expression (6.5.7).