{"record":{"id":"4fa55a8998a327db","repo":"java-native-access/jna","slug":"this-pointer-is-opaque-this","errorCode":null,"errorMessage":"This pointer is opaque: \" + this","messagePattern":"This pointer is opaque: \" \\+ this","errorType":"exception","errorClass":"UnsupportedOperationException","httpStatus":null,"severity":"error","filePath":"src/com/sun/jna/Pointer.java","lineNumber":1204,"sourceCode":"    }\n\n    /** Read the native peer value.  Use with caution. */\n    public static long nativeValue(Pointer p) {\n        return p == null ? 0 : p.peer;\n    }\n\n    /** Set the native peer value.  Use with caution. */\n    public static void nativeValue(Pointer p, long value) {\n        p.peer = value;\n    }\n\n    /** Pointer which disallows all read/write access. */\n    private static class Opaque extends Pointer {\n        private Opaque(long peer) { super(peer); }\n        private final String MSG = \"This pointer is opaque: \" + this;\n        @Override\n        public Pointer share(long offset, long size) {\n            throw new UnsupportedOperationException(MSG);\n        }\n        @Override\n        public void clear(long size) {\n            throw new UnsupportedOperationException(MSG);\n        }\n        @Override\n        public long indexOf(long offset, byte value) {\n            throw new UnsupportedOperationException(MSG);\n        }\n        @Override\n        public void read(long bOff, byte[] buf, int index, int length) {\n            throw new UnsupportedOperationException(MSG);\n        }\n        @Override\n        public void read(long bOff, char[] buf, int index, int length) {\n            throw new UnsupportedOperationException(MSG);\n        }\n        @Override","sourceCodeStart":1186,"sourceCodeEnd":1222,"githubUrl":"https://github.com/java-native-access/jna/blob/d036ad9781adad4b66693e8fa7098e4ac665e0a3/src/com/sun/jna/Pointer.java#L1186-L1222","documentation":"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.","triggerScenarios":"Calling opaquePointer.share(offset, size) where the Pointer was obtained via Pointer.createOpaque / opaque peer (e.g. from Native.getValue of an untyped handle).","commonSituations":"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.","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."],"exampleFix":"// before\nPointer sub = opaquePointer.share(0, size);\n// after\nif (!(opaquePointer instanceof Pointer.Opaque) && opaquePointer != null) {\n    Pointer sub = opaquePointer.share(0, size);\n}","handlingStrategy":"type-guard","validationCode":"// before share():\nif (ptr == null || isOpaque(ptr)) {\n    throw new IllegalStateException(\"Cannot share memory of an opaque pointer\");\n}\nstatic boolean isOpaque(Pointer p) {\n    return p.getClass().getName().equals(\"com.sun.jna.Pointer$Opaque\");\n}","typeGuard":"static boolean isDereferenceable(Pointer p) {\n    return p != null && !p.getClass().getName().equals(\"com.sun.jna.Pointer$Opaque\");\n}","tryCatchPattern":"try {\n    Pointer sub = ptr.share(offset, size);\n} catch (UnsupportedOperationException e) {\n    if (e.getMessage() != null && e.getMessage().startsWith(\"This pointer is opaque\")) {\n        // use the pointer as an opaque handle instead\n    } else throw e;\n}","preventionTips":["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."],"tags":["java","jna","opaque-pointer","unsupported"],"backgroundTag":"unsupported-operation","analyzedSha":"d036ad9781adad4b66693e8fa7098e4ac665e0a3","analyzedAt":"2026-09-12T06:50:59.239Z","contentChangedAt":"2026-09-12T06:50:59.239Z","schemaVersion":2},"datasetVersion":"2026-09-14T11:17:12.474Z"}