macro_rules! probe { ($provider:ident, $name:ident $(, $arg:expr)* $(,)?) => { ... }; }
Expand description
Define a static probe point.
This annotates a code location with a name and arguments, and compiles in metadata to let debugging tools locate it.
Arguments
-
provider
- An identifier for naming probe groups. -
name
- An identifier for this specific probe. -
arg
… - Optional data to provide with the probe. Any expression which can be castas isize
is allowed as an argument. The arguments are always evaluated, even on platforms that have a no-op implementation of probes.
Example
// Probes are unit-typed expressions.
let () = probe!(foo, main);
let x = 42;
probe!(foo, show_x, x);
let y = Some(x);
probe!(foo, show_y, match y {
Some(n) => n,
None => -1
});
let mut z = 0;
probe!(foo, inc_z, { z += 1; z });
assert_eq!(z, 1, "arguments are always evaluated");