What causes "This pointer is opaque: " + this" in java-native-access/jna?

Obtain a real, dereferenceable Pointer (e.g. from Memory allocation or a native function returning a typed pointer) instead of an opaque one.

java-native-access/jna · error · UnsupportedOperationException

This pointer is opaque: " + this

Error message

This pointer is opaque: " + this

What it means

Pointer.Opaque represents a native address (typically from NativeLibrary or a NULL/opaque handle) for which JNA disallows ALL memory access. Calling share(offset, size) on such a pointer throws UnsupportedOperationException because JNA cannot guarantee safe or meaningful reads/writes through it.

Source

Thrown at src/com/sun/jna/Pointer.java:1204

    }

    /** Read the native peer value.  Use with caution. */
    public static long nativeValue(Pointer p) {
        return p == null ? 0 : p.peer;
    }

    /** Set the native peer value.  Use with caution. */
    public static void nativeValue(Pointer p, long value) {
        p.peer = value;
    }

    /** Pointer which disallows all read/write access. */
    private static class Opaque extends Pointer {
        private Opaque(long peer) { super(peer); }
        private final String MSG = "This pointer is opaque: " + this;
        @Override
        public Pointer share(long offset, long size) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void clear(long size) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public long indexOf(long offset, byte value) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void read(long bOff, byte[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override
        public void read(long bOff, char[] buf, int index, int length) {
            throw new UnsupportedOperationException(MSG);
        }
        @Override

View on GitHub (pinned to d036ad9781)

Solutions

Obtain a real, dereferenceable Pointer (e.g. from Memory allocation or a native function returning a typed pointer) instead of an opaque one.
If the pointer is genuinely opaque, store/pass it as a raw Pointer or long handle without dereferencing.
Check for NULL/opaque provenance before calling share(): pointer == null or created via Pointer.createOpaque means skip dereference.
Wrap in try-catch for UnsupportedOperationException if opaque pointers can legitimately flow into shared code.

Example fix

// before
Pointer sub = opaquePointer.share(0, size);
// after
if (!(opaquePointer instanceof Pointer.Opaque) && opaquePointer != null) {
    Pointer sub = opaquePointer.share(0, size);
}

Defensive patterns

Strategy: type-guard

Validate before calling

// before share():
if (ptr == null || isOpaque(ptr)) {
    throw new IllegalStateException("Cannot share memory of an opaque pointer");
}
static boolean isOpaque(Pointer p) {
    return p.getClass().getName().equals("com.sun.jna.Pointer$Opaque");
}

Type guard

static boolean isDereferenceable(Pointer p) {
    return p != null && !p.getClass().getName().equals("com.sun.jna.Pointer$Opaque");
}

Try / catch

try {
    Pointer sub = ptr.share(offset, size);
} catch (UnsupportedOperationException e) {
    if (e.getMessage() != null && e.getMessage().startsWith("This pointer is opaque")) {
        // use the pointer as an opaque handle instead
    } else throw e;
}

Prevention

Track pointer provenance; mark handles from createOpaque as non-dereferenceable in your API.
Never call share/read/write on handles the native side documents as opaque context tokens.
Keep opaque handles as long/Pointer values passed back to native calls untouched.
Centralize pointer dereferencing in one utility that checks opacity first.

When it happens

Trigger: Calling opaquePointer.share(offset, size) where the Pointer was obtained via Pointer.createOpaque / opaque peer (e.g. from Native.getValue of an untyped handle).

Common situations: Receiving an opaque pointer from a native API whose memory layout JNA does not model; accidentally passing an opaque/NULL handle into Structure.read/write, memory sharing, or array APIs.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/4fa55a8998a327db. Report an issue: GitHub.