Previously, the debugger displayed `ref int` variables like this:
ref_int: <unsupported-data-type>
<void>: <unsupported-data-type>
This commit introduces `dbg_variable_to_string()` to dereference these
variables and display their underlying value. Both the command-line and
DAP debugger interfaces have been updated to use this new functionality.
This adds source-level debugging capabilities to the command-line
debugger, utilizing debug information generated by sys4dc. The debug
information format is documented at:
https://github.com/kichikuou/sys4dc/blob/master/docs/debug_info.md
The location of the debug information file can be specified with the
`--debug-info` command-line flag. If not specified, xsystem4 will
attempt to load it from `gamedir_path("src/debug_info.json")`.
When debug information is available, a breakpoint can be set at a
specific line in a file using `breakpoint <file> <line>`. Also, `step`
and `next` commands advance execution to the next source line (this is
naively implemented by repeating instruction-level stepping).
Add 'step' (s) and 'next' (n) commands for single-stepping bytecode.
'step' is the 'step into' type which descends into function calls,
wheras 'next' is the 'step over' type which continues until the next
instruction within the current function.
Add a scene_print function which prints a textual representation of the
current scene. This works by attaching a `debug_print` function to each
entity in the scene. This function is implemented for SACT2 and
GUIEngine entities. A default implementation will be used of none is
provided.
This can be accessed from the debugger via the `scene` command (although
the output is typically too much to view in a terminal; it's better to
run `scene_print` somewhere and redirect stdout to a file).
Read .xsys4-debugrc from ~/.xsystem4 and/or the game directory on
startup. This is just a text file with one debugger command per line.
Can be used to set breakpoints or log functions automatically at
startup.
This can also be used to work around a limitation on Windows where the
IME doesn't work in the debugger, making it impossible to input Japanese
text.
Add vm-state command, which prints disassembly around the current
instruction pointer and the current contents of the stack.
It was necessary to change how breakpoints are implemented for this.
When adding a breakpoint, the original opcode now remains in the
instruction stream, bitwise-or'd with BREAKPOINT. A hash table indexed
by address is used to store breakpoint objects.
* Add "frame" command to change the current frame.
* Add "members" command to print struct members for current frame (if it's
a method frame).
* Support printing member variables (e.g. "this.var") in the "print"
command.
Add a new debugger interface using a simple command language. This is
less powerful than the scheme interface (which still exists) but more
ergonomic for interactive debugging.
This debugger has no external dependencies (it will however use readline
if available) and is included in builds by default.
A sample interaction might look like:
xsystem4 --debug /path/to/game
dbg(cmd)> breakpoint bar
Set breakpoint at function 'bar' (0x00001234)
dbg(cmd)> continue
Hit breakpoint at function 'bar' (0x00001234)
dbg(cmd)> backtrace
#0 0x00001234 in bar
#1 0x00002222 in foo
#2 0x00004444 in main
dbg(cmd)> locals
[0] i: 2
[1] s: "baz"
dbg(cmd)> locals 1
[0] j: 3
[1] obj: { m_i = 0; m_s = "" }
dbg(cmd)> quit
kichikuou