Implements `putchar` when `mgbadebug` build tag is set which outputs
text through the mGBA debugging output interface.
mGBA allows the games running in the emulator to output debug text the
process to do so is:
1. set 0x4FFF780 to value of 0xC0DE
2. write text in memory 0x4FFF600 to 0x4FFF700
3. set 0x4FFF700 to the desired log level value from 0x100 (fatal) to
0x104 (debug)
Once this is done mGBA will output the text in its logs view as well as
through stdout. (Setting the log level to fatal also produces a dialog
box with the text)
The text output in the CLI is prefixed with `[DEBUG] GBA Debug: ` so I
modified the regex used for address matching in panic messages to be
able to read the address when the output line doesn't start with
`panic`.
This adds the same panic locations that are already present for
`tinygo flash -monitor`, but for `tinygo run` and `tinygo test`.
For example, this is the output that I get while working on some GC
code. It now shows the source location instead of just an address:
$ tinygo test -v archive/zip
=== RUN TestReader
=== RUN TestReader/test.zip
panic: runtime error at 0x000000000024d9b4: goroutine stack overflow
[tinygo: panic at /home/ayke/src/tinygo/tinygo/src/internal/task/task_stack.go:58:15]
FAIL archive/zip 0.139s
(This particular location isn't all that useful, but it shows that the
feature works).
The previous commit started printing the instruction address for runtime
panics. This commit starts using this address to print the source
location.
Here is an example where this feature is very useful. There is a heap
allocation in the Bluetooth package, but we don't know where exactly.
Printing the instruction address of the panic is already useful, but
what is even more useful is looking up this address in the DWARF debug
information that's part of the binary:
$ tinygo flash -target=circuitplay-bluefruit -monitor ./examples/heartrate
Connected to /dev/ttyACM0. Press Ctrl-C to exit.
tick 00:00.810
tick 00:01.587
tick 00:02.387
tick 00:03.244
panic: runtime error at 0x00027c4d: alloc in interrupt
[tinygo: panic at /home/ayke/src/tinygo/bluetooth/adapter_sd.go:74:4]
To be clear, this path isn't stored on the microcontroller. It's stored
as part of the build, and `-monitor` just looks up the path from the
panic message.
Possible enhancements:
- Print such an address for regular panics as well. I'm not sure
that's so useful, as it's usually a lot easier to look up panics
just by their message.
- Use runtimePanicAt (instead of runtimePanic) in other locations, if
that proves to be beneficial.
- Print the TinyGo-generated output in some other color, to
distinguish it from the regular console output.
- Print more details when panicking (registers, stack values), and
print an actual backtrace.
zoey
Michael Smith
Ayke van Laethem
sago35