Equivalent of rustc's -Zunpretty=expanded

[aytey]

When working with macros, it is sometimes useful to use rustc's -Zunpretty=expanded flag to see how a macro is being expanded (think of this like -E when working with gcc for C or C++).

I checked the source tree, the tests and the help of a recent build (4d7e7d9), but I couldn't see anything that looked like it matched dumping -Zunpretty=expanded to stdout/stderr/a file.

Is there an equivalent for gccrs?

[aytey]

By way of an example:

${HOME}/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustc ${HOME}/clones/gccrs/gcc/testsuite/rust/execute/torture/macros22.rs -Zunpretty=expanded

Gives:

#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use ::std::prelude::rust_2015::*;
#[macro_use]
extern crate std;
// { dg-output "1\r*\n2\r*\nNaN\r*\n3\r*\n" }

macro_rules! print_num {
    ($l:literal) =>
    { { unsafe { printf("%d\n\0" as *const str as *const i8, $l); } } };
}

extern "C" {
    fn printf(s: *const i8, ...);
}

// Check to make sure that expanding macros does not break the flow of calls
fn main() -> i32 {
    { unsafe { printf("%d\n\0" as *const str as *const i8, 1); } };
    { unsafe { printf("%d\n\0" as *const str as *const i8, 2); } };

    unsafe { printf("NaN\n\0" as *const str as *const i8); }
    {
        unsafe {
            printf("%d\n\0" as *const str as *const i8,
                3);
        }
    };

    0
}

So I was wondering if it is possible to do the same with gccrs.

[P-E-P]

You can use -frust-dump-expansion although it is not 100% perfect for now, it'll insert some comments for tail expressions. Some work is already on track to improve that #3212 should allow more customization and #3209 should fix a slight issue with doc comments being converted to attributes.

[aytey]

Works perfectly -- thank you!