gdbstub VS inlinable-dyn-extension-traits

now integrate gdbstub to support debugging code inside the emulator :)

Shameless plug, but have you considered integrating gdbstub rather than rolling your own debugger? I know a couple folks out there have successfully integrated it into their PS1 emulators with great success.

I've worked really hard to keep gdbstub panic free in its minimal configuration, going so far as to write some informal scripts that parse rustc's asm output to scan for the presence of panicking code paths.

crates.io | docs | repo

As a totally shameless plug, I'm the maintainer of gdbstub, a bare-metal, no_std, no_alloc, and size-optimized implementation of the GDB Remote Serial Protocol. One of the major changes slated for the upcoming release 0.6 is support for a new state-machine based API, which makes it possible to drive gdbstub directly via bare metal interrupt handlers (i.e: send/recv data over UART, handling breakpoints via the undefined instruction trap interrupt, etc...).

Continue working on a new API in gdbstub that'll make it easier to use directly from an interrupt handler when debugging code in a no_std, bare-metal OS environment.

I ran into almost this exact same problem while working on gdbstub, whereby I an API that allowed users to mix/match protocol features however they wanted, while also preventing users from accidentally implementing mutually-exclusive features. Moreover, I wanted to have a "zero cost" way to enable/disable API features without relying on cargo features. The solution I came up with is something I've been calling "Inlineable Dyn Extension Traits", or IDETs.

For a concrete example of how smart the Rust compiler is, I have a small writeup + test-repo that benchmarks a technique I came up with while working on gdbstub that [ab]uses the compiler's devirtualization and inlining optimizations to create runtime feature flags that are entirely compiled out if hard-coded to false at runtime.

In the meantime, you could check out daniel5151/optional-trait-methods for some chicken-scratch notes + exploration on IDETs, including some code samples which you can throw right into godbolt.org to see how well they optimize.

Funny enough, I've also been meaning to write a full blog post about it, but haven't found the time! In the meantime, I've got a rough overview of this technique as part of the gdbstub docs, and I've got a WIP repo of example code and exploratory notes that explores the technique in more detail (along with comparing it with alternative approaches)

Also, check out daniel5151/optional-trait-methods if you haven't already (I point to it near the end of the gdbstub documentation I linked). It's a very rough overview of all the various techniques I considered before landing on IDETs, and includes several simplified examples of how the resulting APIs might work from a implementation and user's perspective.

I've spent quite a bit of time staring at assembly output and performing in-application testing to make sure that optimizations were being triggered as expected.