Clojure/Java: Prevent Exceptions With "trace missing"
Clojure/Java: Prevent Exceptions With "trace missing"
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The other day I got this little helpful exception from Clojure:
(cond (>= nil 1) :unreachable) ;=> NullPointerException [trace missing]
- no line number or anything to troubleshoot it.
It turns out it is not Clojure’s failure but a HotSpot optimization that can apply to NullPointerException, ArithmeticException, ArrayIndexOutOfBoundsException,ArrayStoreException, and ClassCastException. The remedy is to run the JVM with
-XX:-OmitStackTraceInFastThrow
From Oralce JDK release notes:
The compiler in the server VM now provides correct stack backtraces for all “cold” built-in exceptions. For performance purposes, when such an exception is thrown a few times, the method may be recompiled. After recompilation, the compiler may choose a faster tactic using preallocated exceptions that do not provide a stack trace. To disable completely the use of preallocated exceptions, use this new flag:
-XX:-OmitStackTraceInFastThrow.
Many thanks to Ivan Kozik for the info!
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