Embedded debugger

[ColinPitrat]

Provide a tool allowing to:

• examine registers
• disassemble code
• modify code and memory.

[bignaux]

Perhaps a gdb remote would be great https://sourceware.org/gdb/onlinedocs/gdb/Remote-Stub.html

[bfxdev]

There is a Visual-Studio Code Z80 debugger for Spectrum called DeZog. It is interfaced via a simple IP socket connection (typically on localhost), via a documented protocol. Some hints to add a new remote are given too, and there is an implementation as a DLL.

Originally the Debugger was made for the ZX Next and can manage sprite information, in addition to classical Z80 data.

[ColinPitrat]

The Visual-Studio Code option sounds interesting.

Some thoughts on how to implement it in Caprice32 directly (some applies to an external debugger too):

• CPC.break_points provide an address at which z80_execute will stop and return EC_BREAKPOINT
• showGui, userConfirmsQuitWithoutSaving and showVKeyboard are 3 examples of GUI display - the difference here is that we would want to be able to update the back_surface. We may also want a way to see it without the GUI in front of it (or have the GUI next to it and force a higher resolution when using it).
• when stepping, set the break_point to the next address. If we want to be able to step-in, some logic is needed to identify jumps. Another option is to add a support in the code to break at the next instruction no matter what.

[ColinPitrat]

The protocol approach, on network or unix socket, is interesting as it could allow to support multiple debuggers (e.g DeZog + custom one running as a separate process but that can be launched from the UI)

[ColinPitrat]

Development of the debugger has started. It can be invoked with F2 and already supports showing z80 registers, memory content, disassembly. It supports setting breakpoints and watchpoints. Missing features:

• step instruction
• read or write watch points (as opposed to read&write)
• load symbol files
• display stack
• have multiple windows opened at the same time

[ColinPitrat]

I'll call it done at this point although I still have some ideas of features that could be added.