How do I print all attributes?

Question

I want to print the compile-time attributes to the console, ("conditional predicates"). Is there built-in function or macro that does this?

I'm imagining code like:

#[allow(non_snake_case)]
fn main() {
    eprintln!(cfg_as_str!());
}

that might print

allow.non_snake_case=true
allow.dead_code=false
...
cfg.debug_attributes=true
cfg.test=false
cfg.bench=false
...
target_arch="x86_64"
...

I want to better understand the state of the rust compiler at different lines of code. However, it's tedious to do so by trial-and-error.

Of course, I could write this on my own. But I'd guess someone else already has.

Answer 1

I don't think you'll get the lint attributes but for the cfg options you could add a build.rs with:

use std::env;

fn main() {
    for (key, value) in env::vars() {
        if key.starts_with("CARGO") {
            eprintln!("{}: {}", key, value);
        }
    }
}

Then building with cargo build -vv will output cfgs.

See: https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts