# There's an `info!` statement in `codegen_instance` that outputs
# every function that is codegen'd. This is useful to find out
# which function triggers an LLVM assertion, and this is an `info!`
# log rather than a `debug!` log so it will work on the official
# compilers.
$ RUSTC_LOG=rustc_codegen_ssa=info rustc +stage1 my-file.rs

# This will show all logs in `rustc_codegen_ssa` and `rustc_resolve`.
$ RUSTC_LOG=rustc_codegen_ssa,rustc_resolve rustc +stage1 my-file.rs

# This will show the output of all `info!` calls made by rustdoc
# or any rustc library it calls.
$ RUSTDOC_LOG=info rustdoc +stage1 my-file.rs

# This will only show `debug!` calls made by rustdoc directly,
# not any `rustc*` crate.
$ RUSTDOC_LOG=rustdoc=debug rustdoc +stage1 my-file.rs
```

## Log colors

By default, rustc (and other tools, like rustdoc and Miri) will be smart about
when to use ANSI colors in the log output. If they are outputting to a terminal,
they will use colors, and if they are outputting to a file or being piped
somewhere else, they will not. However, it's hard to read log output in your
terminal unless you have a very strict filter, so you may want to pipe the
output to a pager like `less`. But then there won't be any colors, which makes
it hard to pick out what you're looking for!

You can override whether to have colors in log output with the `RUSTC_LOG_COLOR`
environment variable (or `RUSTDOC_LOG_COLOR` for rustdoc, or `MIRI_LOG_COLOR`
for Miri, etc.). There are three options: `auto` (the default), `always`, and
`never`. So, if you want to enable colors when piping to `less`, use something
similar to this command:

```bash
# The `-R` switch tells less to print ANSI colors without escaping them.
$ RUSTC_LOG=debug RUSTC_LOG_COLOR=always rustc +stage1 ... | less -R
```

Note that `MIRI_LOG_COLOR` will only color logs that come from Miri, not logs
from rustc functions that Miri calls. Use `RUSTC_LOG_COLOR` to color logs from
rustc.

## How to keep or remove `debug!` and `trace!` calls from the resulting binary

While calls to `error!`, `warn!` and `info!` are included in every build of the compiler,
calls to `debug!` and `trace!` are only included in the program if