[BUG PROPOSAL]: C++ code that calls JNI_CreateJavaVM can be exited by java

[Adam Farley8]

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.

Issues:

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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