On Fri, 30 Aug 2024 05:21:54 GMT, David Holmes <dhol...@openjdk.org> wrote:
>> This is the implementation of a new method added to the JNI specification. >> >> From the CSR request: >> >> The `GetStringUTFLength` function returns the length as a `jint` (`jsize`) >> value and so is limited to returning at most `Integer.MAX_VALUE`. But a Java >> string can itself consist of `Integer.MAX_VALUE` characters, each of which >> may require more than one byte to represent them in modified UTF-8 format.** >> It follows then that this function cannot return the correct answer for all >> String values and yet the specification makes no mention of this, nor of any >> possible error to report if this situation is encountered. >> >> **The modified UTF-8 format used by the VM can require up to six bytes to >> represent one unicode character, but six byte characters are stored as UTF16 >> surrogate pairs. Hence the most bytes per character is 3, and so the maximum >> length is 3*`Integer.MAX_VALUE`. With compact strings this reduces to >> 2*`Integer.MAX_VALUE`. >> >> Solution >> >> Deprecate the existing JNI `GetStringUTFLength` method noting that it may >> return a truncated length, and add a new method, JNI >> `GetStringUTFLengthAsLong` that returns the string length as a `jlong` value. >> >> --- >> >> We also add a truncation warning to `GetStringUTFLength` under -Xcheck:jni >> >> There are some incidental whitespace changes in >> `src/hotspot/os/posix/dtrace/hotspot_jni.d` along with the new method >> entries. >> >> Testing: >> - new test added >> - tiers 1-3 sanity >> >> Thanks > > David Holmes has updated the pull request incrementally with one additional > commit since the last revision: > > Exclude test on 32-bit Deprecating the existing function and introducing the new function looks okay. The test is really 3 tests in one (GetStringUTFLength returning a truncated size, GetStringUTFLength with -Xcheck:jni prints a warning, and GetStringUTFLengthAsLong returns the long size). Personally I would have done this as 3 test cases rather in one launch with -Xcheck:jni but that's your choice. ------------- Marked as reviewed by alanb (Reviewer). PR Review: https://git.openjdk.org/jdk/pull/20784#pullrequestreview-2275089037
