Command-line arguments

Here's a list of command-line arguments to rustc and what they do.

-h/--help: get help

This flag will print out help information for rustc.

--cfg: configure the compilation environment

This flag can turn on or off various #[cfg] settings.

The value can either be a single identifier or two identifiers separated by =.

For examples, --cfg 'verbose' or --cfg 'feature="serde"'. These correspond to #[cfg(verbose)] and #[cfg(feature = "serde")] respectively.

-L: add a directory to the library search path

When looking for external crates, a directory passed to this flag will be searched.

-l: link the generated crate to a native library

This flag allows you to specify linking to a specific native library when building a crate.

--crate-type: a list of types of crates for the compiler to emit

This instructs rustc on which crate type to build.

--crate-name: specify the name of the crate being built

This informs rustc of the name of your crate.

--emit: emit output other than a crate

Instead of producing a crate, this flag can print out things like the assembly or LLVM-IR.

--print: print compiler information

This flag prints out various information about the compiler.

-g: include debug information

A synonym for -C debug-level=2.

-O: optimize your code

A synonym for -C opt-level=2.

-o: filename of the output

This flag controls the output filename.

--out-dir: directory to write the output in

The outputted crate will be written to this directory.

--explain: provide a detailed explanation of an error message

Each error of rustc's comes with an error code; this will print out a longer explanation of a given error.

--test: build a test harness

When compiling this crate, rustc will ignore your main function and instead produce a test harness.

--target: select a target triple to build

This controls which target to produce.

-W: set lint warnings

This flag will set which lints should be set to the warn level.

-A: set lint allowed

This flag will set which lints should be set to the allow level.

-D: set lint denied

This flag will set which lints should be set to the deny level.

-F: set lint forbidden

This flag will set which lints should be set to the forbid level.

--cap-lints: set the most restrictive lint level

This flag lets you 'cap' lints, for more, see here.

-C/--codegen: code generation options

This flag will allow you to set codegen options.

-V/--version: print a version

This flag will print out rustc's version.

-v/--verbose: use verbose output

This flag, when combined with other flags, makes them produce extra output.

--extern: specify where an external library is located

This flag allows you to pass the name and location of an external crate that will be linked into the crate you're buildling.

--sysroot: Override the system root

The "sysroot" is where rustc looks for the crates that come with the Rust distribution; this flag allows that to be overridden.

--error-format: control how errors are produced

This flag lets you control the format of errors.

--color: configure coloring of output

This flag lets you control color settings of the output.