Instrumenting embedded applications

emit supports embedded and constrained environments, but isn't explicitly targeting them the way frameworks like defmt do.

To use emit in an embedded environment, you'll need to disable default crate features to avoid pulling in the standard library:

[dependencies.emit]
version = "1.13.1"
default-features = false

Configuring a static runtime

emit abstracts everything a diagnostic pipeline needs within a Runtime. Using runtimes, you can customize the clock and source of randomness in environments that don't have an obvious default, or disable them when there isn't one.

extern crate emit;
fn main() {}
// Replace these with your own implementations, or leave as `emit::Empty`
// if they're not supported in your target environment
type Emitter = emit::Empty;
type Filter = emit::Empty;
type Ctxt = emit::Empty;
type Clock = emit::Empty;
type Rng = emit::Empty;

// Define a static runtime using the given components
static MY_RUNTIME: emit::runtime::Runtime<Emitter, Filter, Ctxt, Clock, Rng> = emit::runtime::Runtime::build(
    emit::Empty,
    emit::Empty,
    emit::Empty,
    emit::Empty,
    emit::Empty,
);

Static runtimes can also be used in other environments to avoid dynamic dispatch and improve performance.

Using emit! and #[span]

Embedded environments need to specify a runtime explicitly in the emit! or #[span] macros using the rt control parameter:

extern crate emit;
static MY_RUNTIME: emit::runtime::Runtime<emit::Empty, emit::Empty, emit::Empty, emit::Empty, emit::Empty> = emit::runtime::Runtime::build(emit::Empty, emit::Empty, emit::Empty, emit::Empty, emit::Empty);
fn main() {
let user = "Embedded";

// Use the static runtime, `MY_RUNTIME`, defined previously
emit::emit!(rt: MY_RUNTIME, "Hello, {user}");
}