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Try to avoid a JNA invalid memory error by avoiding the Memory finalizer
That finalizer is known to prematurely free memory, in at least one case[1]. I noticed a non-reproducible "Invalid memory error" from a call to winpty_open that I speculate is a similar problem. [1] java-native-access/jna#664
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|---|---|---|
| @@ -0,0 +1,98 @@ | ||
| package com.pty4j.windows; | ||
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| import com.sun.jna.Memory; | ||
| import com.sun.jna.Pointer; | ||
| import com.sun.jna.platform.win32.WinNT; | ||
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| class ManualAllocation { | ||
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| // Expose the Memory class' protected malloc/free functions. The JNA Memory | ||
| // class' finalizer is capable of freeing memory prematurely[1]. I saw the | ||
| // winpty_open call produce an "Invalid memory access" error (only once, | ||
| // non-reproducibly) when it used a PointerByReference object for its error | ||
| // output parameter. Perhaps the PointerByReference object was somehow | ||
| // finalized too soon? I'm skeptical, but avoiding the Memory finalizer | ||
| // seems prudent. | ||
| // | ||
| // The Manual{Int,HANDLE}ByReferences classes in this module must be | ||
| // explicitly closed. The Java 7 try-with-resources pattern works. | ||
| // | ||
| // [1] https://github.com/java-native-access/jna/issues/664 | ||
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| static class ManualMemory extends Memory { | ||
| static Pointer alloc(long size) { | ||
| long rawPtr = Memory.malloc(size); | ||
| if (rawPtr == 0) { | ||
| throw new OutOfMemoryError("Cannot allocate " + size + " bytes"); | ||
| } | ||
| try { | ||
| Pointer ret = new Pointer(rawPtr); | ||
| rawPtr = 0; | ||
| return ret; | ||
| } finally { | ||
| if (rawPtr != 0) { | ||
| Memory.free(rawPtr); | ||
| } | ||
| } | ||
| } | ||
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| static void free(Pointer ptr) { | ||
| Memory.free(Pointer.nativeValue(ptr)); | ||
| } | ||
| } | ||
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| static class ManualByReference implements AutoCloseable { | ||
| private Pointer ptr; | ||
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| ManualByReference() { | ||
| ptr = ManualMemory.alloc(Pointer.SIZE); | ||
| } | ||
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| Pointer byRef() { | ||
| return ptr; | ||
| } | ||
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| @Override | ||
| public void close() { | ||
| ManualMemory.free(ptr); | ||
| ptr = null; | ||
| } | ||
| } | ||
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| static class ManualHANDLEByReference extends ManualByReference { | ||
| ManualHANDLEByReference() { | ||
| this(null); | ||
| } | ||
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| ManualHANDLEByReference(WinNT.HANDLE value) { | ||
| setValue(value); | ||
| } | ||
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| void setValue(WinNT.HANDLE value) { | ||
| byRef().setPointer(0, value == null ? null : value.getPointer()); | ||
| } | ||
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| WinNT.HANDLE getValue() { | ||
| Pointer value = byRef().getPointer(0); | ||
| return value == null ? null : new WinNT.HANDLE(value); | ||
| } | ||
| } | ||
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| static class ManualIntByReference extends ManualByReference { | ||
| ManualIntByReference() { | ||
| this(0); | ||
| } | ||
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| ManualIntByReference(int value) { | ||
| setValue(value); | ||
| } | ||
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| void setValue(int value) { | ||
| byRef().setInt(0, value); | ||
| } | ||
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| int getValue() { | ||
| return byRef().getInt(0); | ||
| } | ||
| } | ||
| } |
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