On Tue, 24 Jun 2025 00:04:54 GMT, Chen Liang <li...@openjdk.org> wrote:
> Unsafe throws IAE for misusing static vs instance fields, and it's revealed > that AtomicXxxFieldUpdaters are using this mechanism to reject static fields. > This is not a good practice, but we can at least document this so we don't > accidentally introduce problems. I noticed that the native implementation of `Unsafe::array(BaseOffset/IndexScale)` refers to the non‑existent class `java.lang.InvalidClassException` instead of `java.lang.IllegalArgumentException` (which results in `java.lang.NoClassDefFoundError` being thrown): https://github.com/openjdk/jdk/blob/1ca008fd02496dc33e2707c102560cae1690fba5/src/hotspot/share/prims/unsafe.cpp#L587-L594 src/hotspot/share/prims/unsafe.cpp line 498: > 496: if (fs.access_flags().is_static()) { > 497: offset = -1; > 498: } else { Since `offset` is initialised to `-1`, this can simply do: Suggestion: if (!fs.access_flags().is_static()) { src/java.base/share/classes/jdk/internal/misc/Unsafe.java line 1070: > 1068: * > 1069: * @throws NullPointerException if the field is {@code null} > 1070: * @throws IllegalArgumentException if the field is static Maybe these checks could be done in **Java** like: // implicit null check: if ((f.getModifiers() & ACC_STATIC) != 0) { throw new IllegalArgumentException("Field is static"); } and for the `staticField(Offset/Base)` methods: // implicit null check: if ((f.getModifiers() & ACC_STATIC) == 0) { throw new IllegalArgumentException("Field is not static"); } src/java.base/share/classes/jdk/internal/misc/Unsafe.java line 1092: > 1090: * in class {@code c}, i.e., if {@code > c.getDeclaredField(name)} > 1091: * would throw {@code java.lang.NoSuchFieldException}, or > if such > 1092: * a field is static This is actually not the case, the native code only checks whether the field exists, not whether it’s also not `static`: https://github.com/openjdk/jdk/blob/cbcf401170e0600e48ef74770eaa47c84c7e50b0/src/hotspot/share/prims/unsafe.cpp#L492-L503 Suggestion: * would throw {@code java.lang.NoSuchFieldException}. ------------- PR Comment: https://git.openjdk.org/jdk/pull/25945#issuecomment-3007131955 PR Review Comment: https://git.openjdk.org/jdk/pull/25945#discussion_r2164661450 PR Review Comment: https://git.openjdk.org/jdk/pull/25945#discussion_r2164571411 PR Review Comment: https://git.openjdk.org/jdk/pull/25945#discussion_r2164571852
