RFR: 8367129: Move input validation checks to Java for java.lang.StringLatin1 intrinsics [v2]

[Raffaello Giulietti]

On Thu, 12 Feb 2026 16:11:25 GMT, Volkan Yazici <vyazici at openjdk.org> wrote:

>> Moves input validation checks to Java for `java.lang.StringLatin1` intrinsics. While doing so, affected `java.lang.StringUTF16` methods needed to be updated due to relaxed checks at intrinsics. The javadocs of the touched methods are extensively overhauled.
>
> Volkan Yazici has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Apply review feedback

src/java.base/share/classes/java/lang/StringLatin1.java line 174:

> 172:         String.checkOffset(len2, length(other));
> 173:         int lim = Math.min(len1, len2);
> 174:         int k = ArraysSupport.mismatch(value, other, lim);

>From the `mismatch()` doc it isn't clear that the returned index (if not negative) is the _smallest_ one locating a mismatch.
Without this guarantee, this `compareTo()` method might return an incorrect value.

src/java.base/share/classes/java/lang/StringLatin1.java line 199:

> 197:     // inline_string_compareTo
> 198:     @IntrinsicCandidate
> 199:     private static int compareToUTF16_0(byte[] value, byte[] other) {

I guess the `_` is to visually separate the 16 from the conventional 0?
Other intrinsics names, e.g., `compareTo0()` do not use a separator.

src/java.base/share/classes/java/lang/StringLatin1.java line 242:

> 240:     static int compareToCI(byte[] value, byte[] other) {
> 241:         int len1 = value.length;    // Implicit null check on `value`
> 242:         int len2 = other.length;    // Implicit null check on `other`

Alternatively, if you prefer

Suggestion:

        int len1 = value.length;    // fail fast on null
        int len2 = other.length;    // fail fast on null

src/java.base/share/classes/java/lang/StringLatin1.java line 265:

> 263:     static int compareToCI_UTF16(byte[] value, byte[] other) {
> 264:         Objects.requireNonNull(value);
> 265:         Objects.requireNonNull(other);

You could leave these checks out and rely on the following two lines for a fast fail on `null`, similarly to the latin1 case above.
But adding the checks looks cleaner.

src/java.base/share/classes/java/lang/StringLatin1.java line 428:

> 426:      *
> 427:      * @throws NullPointerException if {@code value} is null
> 428:      * @throws StringIndexOutOfBoundsException if the sub-ranges are out of bounds

Suggestion:

     * @throws StringIndexOutOfBoundsException if the sub-range is out of bounds

src/java.base/share/classes/java/lang/StringLatin1.java line 508:

> 506:     @IntrinsicCandidate
> 507:     private static int indexOf0(byte[] value, int valueToIndex, byte[] str, int strToIndex, int valueFromIndex) {
> 508:         byte first = str[0];

There's no protection in the 5 parameter caller agains an empty (0 length) `str`, so this can throw.
I didn't look at the intrinsic to verify whether it assumes `str.length` > 0.

src/java.base/share/classes/java/lang/StringLatin1.java line 1025:

> 1023: 
> 1024:     /**
> 1025:      * Exhaustively copies characters from a Latin-1 string byte array sub-range

Stylistically, why "Exhaustively"?

src/java.base/share/classes/java/lang/StringLatin1.java line 1072:

> 1070:     static void inflate(byte[] src, int srcOff, byte[] dst, int dstOff, int len) {
> 1071:         String.checkBoundsOffCount(srcOff, len, src.length);    // Implicit null check on `src`
> 1072:         Objects.requireNonNull(dst);

As above, you could rely on `StringUTF16.length(dst)` below to fail fast on `null`.
But it looks fine as it is now.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28832#discussion_r2804047503
PR Review Comment: https://git.openjdk.org/jdk/pull/28832#discussion_r2804059770
PR Review Comment: https://git.openjdk.org/jdk/pull/28832#discussion_r2804087560
PR Review Comment: https://git.openjdk.org/jdk/pull/28832#discussion_r2804122486
PR Review Comment: https://git.openjdk.org/jdk/pull/28832#discussion_r2804136126
PR Review Comment: https://git.openjdk.org/jdk/pull/28832#discussion_r2804205561
PR Review Comment: https://git.openjdk.org/jdk/pull/28832#discussion_r2804292351
PR Review Comment: https://git.openjdk.org/jdk/pull/28832#discussion_r2804301436