RFR: 8347408: Create an internal method handle adapter for system calls with errno

[ExE Boss]

On Tue, 26 Nov 2024 15:04:51 GMT, Per Minborg <pminborg at openjdk.org> wrote:

> Going forward, converting older JDK code to use the relatively new FFM API requires system calls that can provide `errno` and the likes to explicitly allocate a MemorySegment to capture potential error states. This can lead to negative performance implications if not designed carefully and also introduces unnecessary code complexity.
> 
> Hence, this PR proposes to add a _JDK internal_ method handle adapter that can be used to handle system calls with `errno`, `GetLastError`, and `WSAGetLastError`.
> 
> It currently relies on a thread-local cache of MemorySegments to allide allocations. If, in the future, a more efficient thread-associated allocation scheme becomes available, we could easily migrate to that one.
> 
> Tested and passed tiers 1-3.

Since the `returnFilter(…)` methods are only ever invoked reflectively by method handle combinators, they can use `throws Throwable`, which avoids possible double‑wrapping of `Error`s (`StackOverflowError` or `OutOfMemoryError`) and `RuntimeException`s:

src/java.base/share/classes/jdk/internal/foreign/CaptureStateUtil.java line 171:

> 169:             throw new InternalError(t);
> 170:         }
> 171:     }

Suggestion:

    private static int returnFilter(MethodHandle errorHandle, int result) throws Throwable {
        if (result >= 0) {
            return result;
        }

        return -(int) errorHandle.invoke();
    }

src/java.base/share/classes/jdk/internal/foreign/CaptureStateUtil.java line 183:

> 181:             throw new InternalError(t);
> 182:         }
> 183:     }

Suggestion:

    private static long returnFilter(MethodHandle errorHandle, long result) throws Throwable {
        if (result >= 0) {
            return result;
        }

        return -(int) errorHandle.invoke();
    }

src/java.base/share/classes/jdk/internal/foreign/ErrnoUtil.java line 122:

> 120:     }
> 121: 
> 122:     // Used reflectively via RETURN_FILTER_MH

Suggestion:

    // Used reflectively via INT_RETURN_FILTER_MH

src/java.base/share/classes/jdk/internal/foreign/ErrnoUtil.java line 127:

> 125:     }
> 126: 
> 127:     // Used reflectively via RETURN_FILTER_MH

Suggestion:

    // Used reflectively via LONG_RETURN_FILTER_MH

src/java.base/share/classes/jdk/internal/foreign/ResultErrno.java line 30:

> 28:  *
> 29:  * @param result the result returned from the native call
> 30:  * @param errno  the errno (if result <= 0) or 0

Suggestion:

 * @param errno  the errno (if result < 0) or 0

-------------

PR Review: https://git.openjdk.org/jdk/pull/22391#pullrequestreview-2465893687
PR Review Comment: https://git.openjdk.org/jdk/pull/22391#discussion_r1861206877
PR Review Comment: https://git.openjdk.org/jdk/pull/22391#discussion_r1861207179
PR Review Comment: https://git.openjdk.org/jdk/pull/22391#discussion_r1860280069
PR Review Comment: https://git.openjdk.org/jdk/pull/22391#discussion_r1860280510
PR Review Comment: https://git.openjdk.org/jdk/pull/22391#discussion_r1859646876