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
Stack traces now list addresses in addition to function names.
Additionally, debugger stack traces number each frame, and the numbers
can be used together with the PRINT-LOCALS function to print the values
of local variables for any frame on the stack.
This is implemented by inserting special opcodes into the game's code.
When the breakpoint handler is finished, it returns the original opcode
so that execute_instruction can continue executing normally.
E.g.
* start xsystem4 with --debug option to drop into debugger immediately
* run (bp "game_main")
* ^d or \exit to close debugger REPL
* ...drop into a debugger REPL again at the game_main function
The 'lint' type in system 4 is NOT a 64-bit integer type. It is actually
a signed 32-bit integer type that is clamped between 0 and INT32_MAX.
Negative numbers can be assigned to a lint using SH_LOCALASSIGN (or at
least, the unofficial compiler emits such code) but LI_* instructions
always produce a positive result.
I'm guessing System40.exe converts lints to 64-bit integers for doing
arithmetic, and then clamps the result to the 32-bit integer range
before writing back to a variable.
This fixes a bug in Sengoku Rance where units would become invincible in
commander battles after their HP fell below zero.
- Create separate directories for source and header files.
- Build code shared between xsystem4 and aindump as a static library.
- Create header dirs gfx/ system4/ and vm/
- Make CG.c/h usable without a running VM
Nunuhara Cabbage