Example
(All of these are unstable, and thus can only be used from a nightly compiler.)
log_syntax!()
#![feature(log_syntax)]
macro_rules! logged_sum {
($base:expr) => {
{ log_syntax!(base = $base); $base }
};
($a:expr, $($rest:expr),+) => {
{ log_syntax!(a = $a, rest = $($rest),+); $a + logged_sum!($($rest),+) }
};
}
const V: u32 = logged_sum!(1, 2, 3);
During compilation, it will print the following to stdout:
a = 1 , rest = 2 , 3
a = 2 , rest = 3
base = 3
--pretty expanded
Run the compiler with:
rustc -Z unstable-options --pretty expanded filename.rs
This will expand all macros and then prints the expanded result to stdout, e.g. the above will probably output:
#![feature(prelude_import)]
#![no_std]
#![feature(log_syntax)]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std as std;
const V: u32 = { false; 1 + { false; 2 + { false; 3 } } };
(This is similar to the -E flag in the C compilers gcc and clang.)
