[DPDK/other Bug 1587] lpm: undefined right shift

[DPDK/other Bug 1587] lpm: undefined right shift

[bugzilla]

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https://bugs.dpdk.org/show_bug.cgi?id=1587

            Bug ID: 1587
           Summary: lpm: undefined right shift
           Product: DPDK
           Version: unspecified
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: other
          Assignee: dev@dpdk.org
          Reporter: stephen@networkplumber.org
  Target Milestone: ---

Both rte_lpm.c and rte_lpm6.c are using >> operator on a negative integer.
According to the C standard the result of that is implementation defined (ie
not portable).

Reported by PVS studio as warning:
https://pvs-studio.com/en/docs/warnings/v610/

static uint32_t __rte_pure
depth_to_mask(uint8_t depth)
{
        VERIFY_DEPTH(depth);

        /* To calculate a mask start with a 1 on the left hand side and right
         * shift while populating the left hand side with 1's
         */
        return (int)0x80000000 >> (depth - 1);
}

and

static uint8_t __rte_pure
depth_to_mask_1b(uint8_t depth)
{
        /* To calculate a mask start with a 1 on the left hand side and right
         * shift while populating the left hand side with 1's
         */
        return (signed char)0x80 >> (depth - 1);
}

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