When we pass unsupported 'jmap' command line option 'jmap' doesn't give any warning/error message and some times it gives following exception.

Unsupported command line option '-F dump:live..' is used in this particular case.

shafi@shafi-ahmad:~/Java/jdk9/jdk9-dev/hotspot$ jps
24227 Test
24345 Jps
shafi@shafi-ahmad:~/Java/jdk9/jdk9-dev/hotspot$ jmap -F -dump:live,format=b,file=heap_dump.hprof 24227
Attaching to process ID 24227, please wait...
Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process
at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.execute(LinuxDebuggerLocal.java:163)
at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach(LinuxDebuggerLocal.java:278)
at sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:671)
at sun.jvm.hotspot.HotSpotAgent.setupDebuggerLinux(HotSpotAgent.java:611)
at sun.jvm.hotspot.HotSpotAgent.setupDebugger(HotSpotAgent.java:337)
at sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:304)
at sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:140)
at sun.jvm.hotspot.tools.Tool.start(Tool.java:185)
at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
at sun.jvm.hotspot.tools.HeapDumper.main(HeapDumper.java:83)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.tools.jmap.JMap.runTool(JMap.java:201)
at sun.tools.jmap.JMap.main(JMap.java:130)
Caused by: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process
at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach0(Native Method)
at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.access$100(LinuxDebuggerLocal.java:62)
at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$1AttachTask.doit(LinuxDebuggerLocal.java:269)
at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.run(LinuxDebuggerLocal.java:138)

$ java -version
java version "1.8.0_66"
Java(TM) SE Runtime Environment (build 1.8.0_66-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.66-b17, mixed mode)

Expected result:
On usage of such unsupported combination 'jmap' should gives warning/error. The best action here is probably to print a warning and then ignore the "live" flag. The alternative would be to print an error and exit, and the user can fix the command.