Hi Adam, 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 ( http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/invocation.html ). 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 installed etc. Kind Regards, Thomas On Wed, Aug 23, 2017 at 5:54 PM, Adam Farley8 <adam.far...@uk.ibm.com> wrote: > 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 > Unless stated otherwise above: > IBM United Kingdom Limited - Registered in England and Wales with number > 741598. > Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU >
