RTEMS | kern_ntptime.c: Negative Shift Value Warning (#5339)

[Joel Sherrill (@joel)]

Joel Sherrill commented on a discussion: https://gitlab.rtems.org/rtems/rtos/rtems/-/issues/5339#note_132733


This warning is generated on all targets and BSPs. Per Section 6.5.7 Bitwise shift operators in the C11 standard, many of the possible cases are undefined behavior:

> The result of E1 \<\< E2 is E1 left-shifted E2 bit positions; vacated bits are filled with zeros. If E1 has an unsigned type, the value of the result is E1 × 2E2, reduced modulo one more than the maximum value representable in the result type. If E1 has a signed type and nonnegative value, and E1 × 2E2 is representable in the result type, then that is the resulting value; otherwise, the behavior is undefined. 
>
> The result of E1 \>\> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type or if E1 has a signed type and a nonnegative value, the value of the result is the integral part of the quotient of E1 /2E2. I f E1 has a signed type and a negative value, the resulting value is implementation-defined.

-- 
View it on GitLab: https://gitlab.rtems.org/rtems/rtos/rtems/-/issues/5339#note_132733
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