A. Sundararajan's Weblog

Mixed mode stack traces on Java exceptions

We all know that Throwable.printStackTrace() prints stack trace containing Java frames. How about printing mixed mode stack trace on exceptions? - we want to print Java frames, JNI C/C++ frames and OS C/C++ frames - all in one place - that too whenever an exception is thrown - regardless of whether user's code had printStackTrace() call or not. i.e., we want this on already compiled, running system. Can we get that? Yes -- if you use DTrace with Mustang (Java SE 6).

Most of the time exceptions are thrown with the following pattern:

   throw new FooException();

hotspot$1:::method-entry {
    self->ptr = (char*)copyin(arg1, arg2+1);
    self->ptr[arg2] = '\0';
    self->classname = (string)self->ptr;
    self->ptr = (char*)copyin(arg3, arg4+1);
    self->ptr[arg4] = '\0';
    self->methodname = (string)self->ptr;
}
hotspot$1:::method-entry 
/ self->classname == "java/lang/Throwable" && self->methodname == "<init>" / {
   jstack();
}

How this D-script works? All Java exceptions and errors are directly or indirectly derived from java.lang.Throwable. So, all exception constructors will eventually call constructor of java.lang.Throwable -- we put a method-entry probe with filter for that constructor (note that <init> is internal name for constructor methods). On every Throwable constructor call, we print mixed mode stack trace using jstack built-in function.

Note that to use method-entry probe, you need to start your Java application with the flag -XX:+ExtendedDTraceProbes - but this requirement may change in Mustang FCS.

Mustang offers great tools, APIs for observability. This is one of the many reasons why you may want to try Mustang - beta is available now!

( Feb 15 2006, 08:51:18 PM IST ) Permalink Comments [2] | | | | |