RFR (S): 8210242: vmTestbase/nsk/stress/jni/jnistress001.java crashes with EXCEPTION_ACCESS_VIOLATION on windows-x86
lois.foltan at oracle.com
Thu Oct 25 11:00:44 UTC 2018
Looks good David.
On 10/25/2018 2:03 AM, David Holmes wrote:
> Bug: https://bugs.openjdk.java.net/browse/JDK-8210242
> webrev: http://cr.openjdk.java.net/~dholmes/8210242/webrev/
> The fundamental bug here was that a character array was copied without
> attempting to copy**/add a NUL terminating character so it formed a
> valid C string (char*). The array was passed to printf %s and by good
> fortune happened to have a NUL 99% of the time, occasionally had a
> junk character or two that would at least print okay on Linux etc but
> once in a blue moon would trigger an EXCEPTION_ACCESS_VIOLATION on
> ** There's actually no guarantee the original array was itself
> NUL-terminated (hotspot does do so but the JNI spec does not require
> it) - but that's a cleanup for later - see below.
> The fix I chose for that was to use %.*s and pass the actual length.
> The main reason I chose that was to reinforce that arrays need not be
> NUL-terminated and we should get out of that mind set when working
> with Java Strings and JNI. In doing that I factored an expression:
> (sometimes expressed as index-1 due to index being sneakily
> incremented in the middle of the code), into a local variable elem_len.
> In addition, due to thinking it may be the cause of the problem, I
> introduced a utility function c_malloc to check malloc does not return
> NULL and to fail if it does. So all mallocs became c_malloc calls.
> There is a lot of potential cleanup possible in this test and the
> others in Testbase/nsk/stress/jni/ but I had neither the time nor the
> inclination to clean up what is in places truly awful code. So I filed
> a follow RFE for someone else to do that cleanup:
> - local testing showed corrupted names before the fix and no
> corruption afterwards
> - Windows specific testing showed 1 in 50 crash before and no
> crashes in 210 after
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