On Fri, 30 Oct 2026 15:04:31 GMT, Jorn Vernee <[email protected]> wrote:
>> Currently we do not directly support unsigned types in the Linker. The >> javadoc has this to say about it: >> >>> A native linker typically does not provide canonical layouts for C's >>> unsigned integral >> types. Instead, they are modeled using the canonical layouts associated >> with their >> corresponding signed integral types. For instance, the C type `unsigned >> long` >> maps to the canonical layout for `code long`. >> >> This was done under the earlier assumption that ABIs treat signed and >> unsigned types the same. However, it turns out that we missed certain cases >> where this does matter for some ABIs. More concretely: >> >> - Mac x64 and AArch64 ABIs require integral types smaller than `int` to be >> widened to `int` before being passed to a function >> [1](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms), >> >> [2](https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms). >> Clang even extends this behavior to Linux x64 (although this appears to be >> a bug) >> [3](https://mail.openjdk.org/archives/list/[email protected]/message/RJNMKNUXN7R5PSJETZKX3PMBJ7P6GYJG/). >> - RISCV requires arguments smaller than XLEN to be extended to 32 bits >> according to their sign, and then sign extended to XLEN >> [4](https://docs.riscv.org/reference/abi/v1.0/riscv-cc-procedure-calling-convention.html). >> - PowerPC requires small integer types (char, short, int, long, enum) to be >> extended to long >> [5](https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html#PARAM-PASS). >> >> In order to address these use cases we need to attach a bit of extra >> information to a linkage request that indicates the signedness of certain >> arguments. For this patch, we've chosen to attach that information directly >> to the argument layouts through a newly introduced `boolean isSigned()` >> method on a new `ValueLayout` subclass `OfIntegral` that is implemented by >> `OfByte`, `OfShort`, `OfInt`, and `OfLong`. >> >> This information is potentially used by the linker to implement the correct >> extension. In cases where it doesn't affect the way functions are linker the >> information is erased in order to provide more efficient caching, since >> signed and unsigned types can share the same downcall handle in that case. >> >> Testing: `jdk_foreign` test suite on Windows/Linux/Mac-x64, >> Mac/Linux-AArch64, Linux-x64 using the fallback linker. >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](http... > > Jorn Vernee has updated the pull request incrementally with one additional > commit since the last revision: > > re-add requires tag I have seen test errors while running tools/sincechecker/modules/java.base/JavaBaseCheckSince.java: src/java.base/java/lang/foreign/ValueLayout.java:255 method: java.lang.foreign.ValueLayout.OfByte java.lang.foreign.ValueLayout.OfByte.withSignedness(boolean): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:333 method: java.lang.foreign.ValueLayout.OfShort java.lang.foreign.ValueLayout.OfShort.withSignedness(boolean): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:375 method: java.lang.foreign.ValueLayout.OfInt java.lang.foreign.ValueLayout.OfInt.withSignedness(boolean): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:452 method: java.lang.foreign.ValueLayout.OfLong java.lang.foreign.ValueLayout.OfLong.withSignedness(boolean): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:142 class: java.lang.foreign.ValueLayout.OfIntegral: `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:147 method: boolean java.lang.foreign.ValueLayout.OfIntegral.isSigned(): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:155 method: java.lang.foreign.ValueLayout.OfIntegral java.lang.foreign.ValueLayout.OfIntegral.withSignedness(boolean): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:160 method: java.lang.foreign.ValueLayout.OfIntegral java.lang.foreign.ValueLayout.OfIntegral.withName(java.lang.String): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:166 method: java.lang.foreign.ValueLayout.OfIntegral java.lang.foreign.ValueLayout.OfIntegral.withoutName(): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:173 method: java.lang.foreign.ValueLayout.OfIntegral java.lang.foreign.ValueLayout.OfIntegral.withByteAlignment(long): `@since` version: 22; should be: 28 src/java.base/java/lang/foreign/ValueLayout.java:179 method: java.lang.foreign.ValueLayout.OfIntegral java.lang.foreign.ValueLayout.OfIntegral.withOrder(java.nio.ByteOrder): `@since` version: 22; should be: 28 ------------- PR Comment: https://git.openjdk.org/jdk/pull/33417#issuecomment-6574130855
