5038439: Warning message for literal shift amounts outside the canonical domain

[archiecobbs]

When bit shifting an int or long value by an amount X, all but the last 5 or 6 (respectively) bits of X are ignored.

This can create a trap for the unwary, as in this example:

public long readLongBigEndian(byte[] buf, int offset) {
    return ((buf[offset + 0] & 0xff) << 56)   // BUG HERE
         | ((buf[offset + 1] & 0xff) << 48)   // BUG HERE
         | ((buf[offset + 2] & 0xff) << 40)   // BUG HERE
         | ((buf[offset + 3] & 0xff) << 32)   // BUG HERE
         | ((buf[offset + 4] & 0xff) << 24)
         | ((buf[offset + 5] & 0xff) << 16)
         | ((buf[offset + 6] & 0xff) << 8)
         | ((buf[offset + 7] & 0xff);
}

This PR adds a new warning when the compiler detects an out-of-range bit shift, i.e., an int bit shift not in the range [0...31] or a long bit shift not in the range [0...63].

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change requires CSR request JDK-8366919 to be approved

Issues

• JDK-5038439: Warning message for literal shift amounts outside the canonical domain (Enhancement - P4)
• JDK-8366919: Warning message for literal shift amounts outside the canonical domain (CSR)

Reviewing

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[archiecobbs]

/csr

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[openjdk]

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[openjdk]

@archiecobbs has indicated that a compatibility and specification (CSR) request is needed for this pull request.

@archiecobbs please create a CSR request for issue JDK-5038439 with the correct fix version. This pull request cannot be integrated until the CSR request is approved.

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