Evaluation order
Consider this log invocation:
#![allow(unused)] fn main() { extern crate defmt; defmt::info!("x={=?}", foo()); fn foo() -> u8 { defmt::info!("Hello"); 42 } }
Depending on when foo
is invoked this can result in potential re-entrancy / nesting and cause info!("Hello")
to be lost.
So we'll make the macro evaluate format arguments before the acquire operation.
Something like this:
(core::fmt
does a similar match
operation)
#![allow(unused)] fn main() { struct Logger; impl Logger { fn acquire() -> Option<Self> { None } } fn foo() -> u8 { 0 } match (foo()) { // evaluate formatting arguments (_0) => { if let Some(logger) = Logger::acquire() { // serialize `_0`, etc. } } } }