31 Oktober 2000 SEESCOASEESCOA STWW - Programma Work Package 5 – Debugging Task Generic Debug Interface K. De Bosschere e.a.

SEESCOASEESCOA Goals  Define a debug-interface for components  Trace behaviour of components  Limit trace information  Checkpointing and replay of components  Must always be applicable to the system, not just during development

SEESCOASEESCOA Types of Debugging  Many types of debugging are possible  correctness debugging: where is the bug?  performance debugging: why is it so slow? (or fast?)  'exploratory' debugging: what does it do? How does it do it? ...  Many types of programs to debug  own source or third party libraries?  IO intensive or CPU bound?  text interface or GUI? ...  Many types of hardware to debug on/with  large workstations or small embedded systems  network access, GUI or text ...

SEESCOASEESCOA Requirements  Many types of information are required:  tracing of events:  method calls  accesses to objects  I/O  events from the component system  timing:  methods  I/O  resources:  heap  stack  locks

SEESCOASEESCOA Problems: Conclusions  So, the approach to debugging is linked to:  the type of debugging  the type of application being debugged  the type of hardware available  Requirements are varied and sometimes consume large amounts of resources  We need a flexible debugging solution:  all types of debugging must be possible  it must be possible to select only the debugging mechanisms we need  We need a flexible debugging solution:  all types of debugging must be possible  it must be possible to select only the debugging mechanisms we need

SEESCOASEESCOA Embedded System Standard embedded JVM configuration  Normal operation of embedded system + JVM JVM Input/Output Class

SEESCOASEESCOA Debugging Configuration on Board  Specialised instrumentation of class files  On the embedded system Embedded System JVM Input/Output Class Debug JVM Debug JVM

SEESCOASEESCOA Instrumentor Debugging Configuration on Two Systems  Specialised instrumentation of class files  Debugger is different system: minimal interference while maintaining high flexibility i.e. a component Embedded System JVM Input/Output Class Debug JVM Debug JVM Cache

SEESCOASEESCOA Potential Applications  Simple:  Print out activation tree  Time method calls ...  More complex:  Patch erroneous code  Analyse memory allocation  Trace arguments  Execution replay of non-deterministic multi-threaded applications  Tracing of some or all IO ...

SEESCOASEESCOA Developping Debugger module: Record/Replay  Multiple threads  Interleaving produces different results  Non-deterministic A=9 A=5 +Record all non-deterministic behaviour to trace and replay with this trace

SEESCOASEESCOA Future  Perfect the instrumentation layer  Implement a number of modules on top of this layer with useful functionality  Integrate with the component communication system  Further development of record/replay module

SEESCOASEESCOA Conclusions  Debugging is a very specific activity for which the requirements can vary greatly  Embedded systems have only a limited amount of resources  We propose to dynamically alter the bytecode to tailor the debugging facilities to the debug problem and the available hardware  We are currently developing debug facilities on top of this module