[BUG PROPOSAL]: C++ code that calls JNI_CreateJavaVM can be exited by java
thomas.stuefe at gmail.com
Wed Aug 23 17:45:12 UTC 2017
would the JNI exit hook not solve your problem (JavaVMOption "exit")? One
could use it to intercept any exit(2) calls.
However, I am not sure it always fires, and if it does not, whether this
should be considered a bug. The official JNI documentation is pretty sparse
Another thing, even if one catches ::exit(), if the VM creation failed the
process can be in an undefined state, because I am not sure we clean up
orderly for every error exit. So, e.g., signal handlers may still be
Kind Regards, Thomas
On Wed, Aug 23, 2017 at 5:54 PM, Adam Farley8 <adam.farley at uk.ibm.com>
> Hi All,
> Problem: Several of Java's "c" files call exit(0) if you pass certain
> command-line options to JNI_CreateJavaVM, which can terminate the C++ code
> JNI users use to initialise the JVM.
> Example: If you write some C++ code that calls JNI_CreateJavaVM, and uses
> the option "-agentlib:jdwp=help", Java's c files will print the needed
> help output and call exit(0).
> Result: Your C++ code is terminated on this line, and a return code of 0
> is produced.
> Issue 1: The exit(0) prevents your code from doing anything useful after
> the JNI_CreateJavaVM call.
> Issue 2: The exit(0) indicates to anything monitoring your C++ code that
> your code exited normally, even though it was terminated mid-way-through.
> Issue 3: This return code is useless to us, as a 0 can indicate the VM
> started correctly, or it can indicate the VM was terminated due to one or
> more of these command-line options.
> Issue 4: Of the other JNI return values (JNI_OK, JNI_ERR, etc) none of
> them appear to cover this scenario.
> Proposed solutions:
> PS1: We should amend the JNI specification to include a "JNI_SILENT_EXIT"
> return code, so the C++ code knows a VM was not created, but that it isn't
> an error.
> PS2: We should identify a list of the command-line options that produce
> this behaviour via the JNI. (not all of the "help" options are recognised
> by the JNI interface. E.g. -version and -help produce a JNI_ERR and an
> "Option not recognised" message)
> PS3: We should replace these annoying exit(0) calls with code that returns
> "JNI_SILENT_EXIT", so the C++ code has a chance to finish.
> Best Regards
> Adam Farley
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