4. Data Structures

The existing LineNumberTable and LocalVariableTable data structures will be used. A few lookup routines are yet to be written.

Proposal:

• Add a boolean value indicating whether the variable is in a register or stack and another (possibly a byte) to hold the register number if in a register.
• Associate local variable names with primitive graph nodes

Possible problems:

A single variable assigned in more than one place, which gives rise to several different variables in the SSA form and the register allocator allocates a different register to these copies. Then finding the value of a local variable at runtime requires us to figure out exactly what register the variable is in, at that point in time.

Proposed Solution:

See section Finding the values of local variables

4.1 Debugger object

A debugger object will be implemented and shall be used to hold the state of the debugger, including the set of breakpoints set and the active/passive ones.

4.2 PC to byte code mapping

See section Finding the values of local variables

4.3 Bytecode, local varible name -> location mapping

See section Finding the values of local variables