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Merged
ktoso merged 2 commits into from
May 20, 2026
Merged

Detect double destruction and generalize $createDestroyFunction #760

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4cd8c16
Add generic createDestroyFunction impl and add double free check
sidepelican May 20, 2026
ca07baf
Fix tests
sidepelican May 20, 2026
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54 changes: 0 additions & 54 deletions Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -383,8 +383,6 @@ extension JNISwift2JavaGenerator {
"""
)
printer.println()

printDestroyFunction(&printer, decl)
}
}

Expand Down Expand Up @@ -876,58 +874,6 @@ extension JNISwift2JavaGenerator {
}
}

/// Prints the destroy function for a `JNISwiftInstance`
private func printDestroyFunction(_ printer: inout CodePrinter, _ type: ImportedNominalType) {
let funcName = "$createDestroyFunction"
let isEffectivelyGeneric = type.swiftNominal.isGeneric && !type.isSpecialization
let typeName = type.effectiveJavaSimpleName
printer.print("@Override")
printer.printBraceBlock("public Runnable \(funcName)()") { printer in
printer.print("long self$ = this.$memoryAddress();")
printer.print("long selfType$ = this.$typeMetadataAddress();")
if isEffectivelyGeneric {
printer.print(
"""
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("\(typeName).\(funcName)",
"this", this,
"self", self$,
"selfType", selfType$);
}
return new Runnable() {
@Override
public void run() {
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("\(typeName).$destroy", "self", self$, "selfType", selfType$);
}
SwiftObjects.destroy(self$, selfType$);
}
};
"""
)
} else {
printer.print(
"""
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("\(typeName).\(funcName)",
"this", this,
"self", self$);
}
return new Runnable() {
@Override
public void run() {
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("\(typeName).$destroy", "self", self$);
}
SwiftObjects.destroy(self$, selfType$);
}
};
"""
)
}
}
}

private func printFoundationDateHelpers(_ printer: inout CodePrinter, _ decl: ImportedNominalType) {
printer.print(
"""
Expand Down
9 changes: 9 additions & 0 deletions Sources/SwiftJava/SwiftObjects.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -89,4 +89,13 @@ extension SwiftObjects {
}
return perform(as: typeMetadata)
}

@JavaMethod
public static func typeDescription(environment: UnsafeMutablePointer<JNIEnv?>!, selfTypePointer: Int64) -> String {
guard let selfType$ = UnsafeRawPointer(bitPattern: Int(selfTypePointer)) else {
fatalError("selfType metadata address was null")
}
let typeMetadata = unsafeBitCast(selfType$, to: Any.Type.self)
return String(describing: typeMetadata)
}
}
33 changes: 28 additions & 5 deletions SwiftKitCore/src/main/java/org/swift/swiftkit/core/JNISwiftInstance.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,15 +27,38 @@ public interface JNISwiftInstance extends SwiftInstance {
*
* @return a function that is called when the value should be destroyed.
*/
Runnable $createDestroyFunction();
default Runnable $createDestroyFunction() {
var memoryAddress = $memoryAddress();
var typeMetadataAddress = $typeMetadataAddress();
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.trace(
"this", this,
"self", memoryAddress,
"selfType", SwiftObjects.typeDescription(typeMetadataAddress)
);
}
return () -> {
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall(
"SwiftObjects.destroy",
"self", memoryAddress,
"selfType", SwiftObjects.typeDescription(typeMetadataAddress)
);
}
SwiftObjects.destroy(memoryAddress, typeMetadataAddress);
};
}

/**
* The Swift type metadata address of this type.
*/
long $typeMetadataAddress();

@Override
default SwiftInstanceCleanup $createCleanup() {
var statusDestroyedFlag = $statusDestroyedFlag();
Runnable markAsDestroyed = () -> statusDestroyedFlag.set(true);

return new JNISwiftInstanceCleanup(this.$createDestroyFunction(), markAsDestroyed);
return new JNISwiftInstanceCleanup(
$createDestroyFunction(),
$statusDestroyedFlag()
);
}
}
15 changes: 10 additions & 5 deletions SwiftKitCore/src/main/java/org/swift/swiftkit/core/JNISwiftInstanceCleanup.java
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Original file line number Diff line number Diff line change
Expand Up @@ -14,18 +14,23 @@

package org.swift.swiftkit.core;

import java.util.concurrent.atomic.AtomicBoolean;

class JNISwiftInstanceCleanup implements SwiftInstanceCleanup {
private final Runnable destroyFunction;
private final Runnable markAsDestroyed;
private final AtomicBoolean statusDestroyedFlag;

public JNISwiftInstanceCleanup(Runnable destroyFunction, Runnable markAsDestroyed) {
public JNISwiftInstanceCleanup(Runnable destroyFunction, AtomicBoolean statusDestroyedFlag) {
this.destroyFunction = destroyFunction;
this.markAsDestroyed = markAsDestroyed;
this.statusDestroyedFlag = statusDestroyedFlag;
}

@Override
public void run() {
markAsDestroyed.run();
destroyFunction.run();
if (statusDestroyedFlag.compareAndSet(false, true)) {
destroyFunction.run();
} else {
throw new IllegalStateException("Double destruction attempt detected!");
}
}
}
1 change: 1 addition & 0 deletions SwiftKitCore/src/main/java/org/swift/swiftkit/core/SwiftObjects.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,4 +28,5 @@ public static void requireNonZero(long number, String name) {
public static native String toString(long selfPointer, long selfTypePointer);
public static native String toDebugString(long selfPointer, long selfTypePointer);
public static native void destroy(long selfPointer, long selfTypePointer);
public static native String typeDescription(long selfTypePointer);
}
5 changes: 1 addition & 4 deletions SwiftKitFFM/src/main/java/org/swift/swiftkit/ffm/FFMSwiftErrorInstance.java
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Expand Up @@ -61,13 +61,10 @@ protected FFMSwiftErrorInstance(MemorySegment segment, AllocatingSwiftArena aren

@Override
public SwiftInstanceCleanup $createCleanup() {
var statusDestroyedFlag = $statusDestroyedFlag();
Runnable markAsDestroyed = () -> statusDestroyedFlag.set(true);

return new FFMSwiftInstanceCleanup(
$memorySegment(),
$swiftType(),
markAsDestroyed
$statusDestroyedFlag()
);
}
}
5 changes: 1 addition & 4 deletions SwiftKitFFM/src/main/java/org/swift/swiftkit/ffm/FFMSwiftInstance.java
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Original file line number Diff line number Diff line change
Expand Up @@ -70,13 +70,10 @@ protected FFMSwiftInstance(MemorySegment segment, AllocatingSwiftArena arena) {

@Override
public SwiftInstanceCleanup $createCleanup() {
var statusDestroyedFlag = $statusDestroyedFlag();
Runnable markAsDestroyed = () -> statusDestroyedFlag.set(true);

return new FFMSwiftInstanceCleanup(
$memorySegment(),
$swiftType(),
markAsDestroyed
$statusDestroyedFlag()
);
}

Expand Down
21 changes: 12 additions & 9 deletions SwiftKitFFM/src/main/java/org/swift/swiftkit/ffm/FFMSwiftInstanceCleanup.java
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Expand Up @@ -19,26 +19,29 @@
import static org.swift.swiftkit.ffm.SwiftJavaLogGroup.LIFECYCLE;

import java.lang.foreign.MemorySegment;
import java.util.concurrent.atomic.AtomicBoolean;

public class FFMSwiftInstanceCleanup implements SwiftInstanceCleanup {
private final MemorySegment memoryAddress;
private final SwiftAnyType type;
private final Runnable markAsDestroyed;
private final AtomicBoolean statusDestroyedFlag;
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Collaborator

@ktoso ktoso May 20, 2026

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We could move to atomic field updater here, but I'm happy to do this separately


public FFMSwiftInstanceCleanup(MemorySegment memoryAddress, SwiftAnyType type, Runnable markAsDestroyed) {
public FFMSwiftInstanceCleanup(MemorySegment memoryAddress, SwiftAnyType type, AtomicBoolean statusDestroyedFlag) {
this.memoryAddress = memoryAddress;
this.type = type;
this.markAsDestroyed = markAsDestroyed;
this.statusDestroyedFlag = statusDestroyedFlag;
}

@Override
public void run() {
markAsDestroyed.run();

// Allow null pointers just for AutoArena tests.
if (type != null && memoryAddress != null) {
SwiftRuntime.log(LIFECYCLE, "Destroy swift value [" + type.getSwiftName() + "]: " + memoryAddress);
SwiftValueWitnessTable.destroy(type, memoryAddress);
if (statusDestroyedFlag.compareAndSet(false, true)) {
// Allow null pointers just for AutoArena tests.
if (type != null && memoryAddress != null) {
SwiftRuntime.log(LIFECYCLE, "Destroy swift value [" + type.getSwiftName() + "]: " + memoryAddress);
SwiftValueWitnessTable.destroy(type, memoryAddress);
}
} else {
throw new IllegalStateException("Double destruction attempt detected!");
}
}
}
27 changes: 0 additions & 27 deletions Tests/JExtractSwiftTests/JNI/JNIClassTests.swift
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Expand Up @@ -97,33 +97,6 @@ struct JNIClassTests {
""",
]
)
try assertOutput(
input: source,
.jni,
.java,
expectedChunks: [
"""
@Override
public Runnable $createDestroyFunction() {
long self$ = this.$memoryAddress();
long selfType$ = this.$typeMetadataAddress();
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("MyClass.$createDestroyFunction",
"this", this,
"self", self$);
}
return new Runnable() {
@Override
public void run() {
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("MyClass.$destroy", "self", self$);
}
SwiftObjects.destroy(self$, selfType$);
}
};
"""
]
)
}

@Test
Expand Down
21 changes: 0 additions & 21 deletions Tests/JExtractSwiftTests/JNI/JNIEnumTests.swift
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Expand Up @@ -83,27 +83,6 @@ struct JNIEnumTests {
return new MyEnum(selfPointer, swiftArena);
}
""",
"""
@Override
public Runnable $createDestroyFunction() {
long self$ = this.$memoryAddress();
long selfType$ = this.$typeMetadataAddress();
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("MyEnum.$createDestroyFunction",
"this", this,
"self", self$);
}
return new Runnable() {
@Override
public void run() {
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("MyEnum.$destroy", "self", self$);
}
SwiftObjects.destroy(self$, selfType$);
}
};
}
""",
]
)
}
Expand Down
22 changes: 0 additions & 22 deletions Tests/JExtractSwiftTests/JNI/JNIGenericTypeTests.swift
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Expand Up @@ -76,28 +76,6 @@ struct JNIGenericTypeTests {
return this.selfTypePointer;
}
""",
"""
@Override
public Runnable $createDestroyFunction() {
long self$ = this.$memoryAddress();
long selfType$ = this.$typeMetadataAddress();
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("MyID.$createDestroyFunction",
"this", this,
"self", self$,
"selfType", selfType$);
}
return new Runnable() {
@Override
public void run() {
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("MyID.$destroy", "self", self$, "selfType", selfType$);
}
SwiftObjects.destroy(self$, selfType$);
}
};
}
""",
]
)
}
Expand Down
28 changes: 0 additions & 28 deletions Tests/JExtractSwiftTests/JNI/JNIStructTests.swift
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Expand Up @@ -83,34 +83,6 @@ struct JNIStructTests {
""",
]
)
try assertOutput(
input: source,
.jni,
.java,
expectedChunks: [
"""
@Override
public Runnable $createDestroyFunction() {
long self$ = this.$memoryAddress();
long selfType$ = this.$typeMetadataAddress();
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("MyStruct.$createDestroyFunction",
"this", this,
"self", self$);
}
return new Runnable() {
@Override
public void run() {
if (CallTraces.TRACE_DOWNCALLS) {
CallTraces.traceDowncall("MyStruct.$destroy", "self", self$);
}
SwiftObjects.destroy(self$, selfType$);
}
};
}
"""
]
)
}

@Test
Expand Down
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