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swankjesse/Test.kt

Created February 4, 2025 14:45
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Test.kt
@Test
fun closeAJarFileWhileSomebodyIsReadingIt() {
val someJarResource = this::class.java.classLoader.getResource("LICENSE-junit.txt")!!
val connectionA = someJarResource.openConnection()
val sourceA = connectionA.getInputStream().source().buffer()
val connectionB = someJarResource.openConnection()
val sourceB = connectionB.getInputStream().source().buffer()
connectionA.useCaches = false
assertThat(sourceA.readUtf8()).contains("JUnit")
sourceA.close()
assertThat(sourceB.readUtf8()).contains("JUnit")
sourceB.close()
}
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swankjesse commented Feb 4, 2025

This crashes on line 15:

Stream closed
java.io.IOException: Stream closed
	at java.base/java.util.zip.InflaterInputStream.ensureOpen(InflaterInputStream.java:68)
	at java.base/java.util.zip.InflaterInputStream.read(InflaterInputStream.java:143)
	at java.base/java.io.FilterInputStream.read(FilterInputStream.java:119)
	at okio.InputStreamSource.read(JvmOkio.kt:93)
	at okio.Buffer.writeAll(Buffer.kt:1309)
	at okio.RealBufferedSource.readUtf8(RealBufferedSource.kt:325)
	at closeAJarFileWhileSomebodyIsReadingIt(FileLeakTest.kt:172)

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swankjesse commented Feb 4, 2025

It doesn’t crash if you remove this line:

connectionA.useCaches = false

And it doesn’t crash if you don’t open sourceB until after closing sourceA.

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swankjesse commented Feb 4, 2025

Setting useCaches to false causes sourceA to close a .jar file that it doesn’t own.

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jclyne commented Feb 4, 2025

awesome! explains the race condition

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