The MMIX Debugger Options

You reach the MMIX debugger options through the Options menu.

Inspecting Registers and Memory

In the two boxes on top of the dialog, you can select windows that should open automatically when you start the debugger. In the example above, the window showing the local registers and the register stack will open; further a windows showing the Data Segment. All the other windows, for example one for the global registers, can be opened manually when needed.

Choosing Special Registers for display

Next to the checkbox for the special registers is a Choose button. Pressing it opens a dialog where you can choose which registers to display in the special register window. Depending on the problem you are trying to debug, some registers may be relevant and others not at all. Only the registers selected here will be shown in the special register window.

Customizing Tracing

Show Trace:
If the checkbox is selected, the trace window will open and a detailed trace of the instructions is printed when the program stops or hits a tracepoint. Otherwise, the program will run silent.
Break at Main:
If this checkbox is selected, a breakpoint is added automaticaly at Main. So the program will stop as soon as it enters the Main program.
Break after instruction: or
Break before instruction:
Here you can select whether the program stops before or after executing the instruction. This applies to breakpoints as well as to single stepping.
The "classic" behaviour of the MMIX debuger is to stop after the instruction, so that you can see in the trace what the instruction just has done.
Other source code debuggers (for example gdb) usualy stop before executing the instruction. This has the advantage, that you can inspect registers and memory before the instruction, that advance the program to the next instruction and see the changes. It can also be convenient to stop at a branch instruction before it gets executed and then see where it will take the machine.
Enable stack tracing:
If this box is checked, the trace will show details of the hidden register stack while tracing. This is equivalent to the -r option of the mmix simulator.
Trace exceptions:
If this box is checked, all instructions that cause an arithmetic exception will be shown in the trace. This is equivalent to the -e option of the mmix simulator.
If this box is unchecked, no such information is given.
If the box is shaded, a subset of the eight possible arithmetic exceptions has be selected for tracing. To change the set of traced exceptions press the Choose button to the right. A window will open that lets you select or deselect the various arithmetic exceptions for tracing.
Debug Operating System:
If this box is checked the Operating System is also debuggable. If your focus lies on debugging your program it's important to uncheck this box.

Show Statistics:
If this box is checked you can see statistics after each instruction in the output window.

Warn if no application:
If this box is checked, the debugger will issue a warning message when you try to start a program, but no file is selected for loading into memory. To select a file for loading, or change this selection use the Sources Dialog Box.
The Auto-Close feature for the debug windows is not yet implemented.