parrot_debugger(1) The Parrot Debugger


The Parrot debugger


parrot_debugger programfile
parrot_debugger --script scriptfile programfile


Disassemble the bytecode.

Use this if you have a PBC file but not the PASM.

Load a source code file.
"list" or "l"
List the source code file.
"run" or "r"
Run the program.
"break" or "b"
Add a breakpoint at the line number given or the current line if none is given.

    (pdb) b
    Breakpoint 1 at pos 0
    (pdb) b 10
    Breakpoint 1 at pos 10
"watch" or "w"
Add a watchpoint.
"delete" or "d"
Given a number n, deletes the n-th breakpoint. To delete the first breakpoint:

    (pdb) d 1
    Breakpoint 1 deleted
Disable a breakpoint.
Reenable a disabled breakpoint.
"continue" or "c"
Continue the program execution.
"next" or "n"
Run the next instruction
"eval" or "e"
Run an instruction.
"trace" or "t"
Trace the next instruction. This is equivalent to printing the source of the next instruction and then executing it.
"print" or "p"
Print an interpreter register. If a register I0 has been used, this would look like:

    (pdb) p I0

If no register number is given then all registers of that type will be printed. If the two registers I0 and I1 have been used, then this would look like:

    (pdb) p I
    I0 = 2
    I1 = 5

It would be nice if ``p'' with no arguments printed all registers, but this is currently not the case.

"stack" or "s"
Examine the stack.
Print interpreter information relating to memory allocation and garbage collection.
Toggle garbage collection debugging mode. In gcdebug mode a garbage collection cycle is run before each opcocde, which is the same as using the gcdebug core.
"quit" or "q"
Exit the debugger.
"help" or "h"
Print the help.

Debug Ops

You can also debug Parrot code by using the "debug_init", "debug_load" and "debug_break" ops in ops/debug.ops.
"int main(int argc, char *argv[])"
Reads the PIR, PASM or PBC file from argv[1], loads it, and then calls Parrot_debug().
"static void PDB_run_code(PARROT_INTERP, int argc, char *argv[])"
Run the code, catching exceptions if they are left unhandled.
"static void PDB_printwelcome(void)"
Prints out the welcome string.


  • Initial version by Daniel Grunblatt on 2002.5.19.
  • Start of rewrite - leo 2005.02.16

    The debugger now uses it's own interpreter. User code is run in Interp* debugee. We have:

        ^                            |
        |                            v
        +------------- := -----------+

    Debug commands are mostly run inside the "debugger". User code runs of course in the "debugee".


  • Check the user input for bad commands, it's quite easy to make it bang now, try listing the source before loading or disassembling it.
  • Print the interpreter info.
  • Make the user interface better (add comands history/completion).
  • Some other things I don't remember now because it's late.


Renamed from pdb.c on 2008.7.15