rustc - The Cargo Book

NAME

cargo-rustc - Compile the current package, and pass extra options to the compiler

SYNOPSIS

cargo rustc [OPTIONS] [-- ARGS]

DESCRIPTION

The specified target for the current package (or package specified by -p if provided) will be compiled along with all of its dependencies. The specified ARGS will all be passed to the final compiler invocation, not any of the dependencies. Note that the compiler will still unconditionally receive arguments such as -L, --extern, and --crate-type, and the specified ARGS will simply be added to the compiler invocation.

See https://doc.rust-lang.org/rustc/index.html for documentation on rustc flags.

This command requires that only one target is being compiled when additional arguments are provided. If more than one target is available for the current package the filters of --lib, --bin, etc, must be used to select which target is compiled. To pass flags to all compiler processes spawned by Cargo, use the RUSTFLAGS environment variable or the build.rustflags config value.

OPTIONS

Package Selection

By default, the package in the current working directory is selected. The -p flag can be used to choose a different package in a workspace.

-p SPEC
--package SPEC: The package to build. See cargo-pkgid(1) for the SPEC format.

Target Selection

When no target selection options are given, cargo rustc will build all binary and library targets of the selected package.

Passing target selection flags will build only the specified targets.

--lib: Build the package’s library.
--bin NAME…: Build the specified binary. This flag may be specified multiple times.
--bins: Build all binary targets.
--example NAME…: Build the specified example. This flag may be specified multiple times.
--examples: Build all example targets.
--test NAME…: Build the specified integration test. This flag may be specified multiple times.
--tests: Build all targets in test mode that have the test = true manifest flag set. By default this includes the library and binaries built as unittests, and integration tests. Be aware that this will also build any required dependencies, so the lib target may be built twice (once as a unittest, and once as a dependency for binaries, integration tests, etc.). Targets may be enabled or disabled by setting the test flag in the manifest settings for the target.
--bench NAME…: Build the specified benchmark. This flag may be specified multiple times.
--benches: Build all targets in benchmark mode that have the bench = true manifest flag set. By default this includes the library and binaries built as benchmarks, and bench targets. Be aware that this will also build any required dependencies, so the lib target may be built twice (once as a benchmark, and once as a dependency for binaries, benchmarks, etc.). Targets may be enabled or disabled by setting the bench flag in the manifest settings for the target.
--all-targets: Build all targets. This is equivalent to specifying --lib --bins --tests --benches --examples.

Feature Selection

When no feature options are given, the default feature is activated for every selected package.

--features FEATURES: Space or comma separated list of features to activate. These features only apply to the current directory’s package. Features of direct dependencies may be enabled with <dep-name>/<feature-name> syntax.
--all-features: Activate all available features of all selected packages.
--no-default-features: Do not activate the default feature of the current directory’s package.

Compilation Options

--target TRIPLE: Build for the given architecture. The default is the host architecture. The general format of the triple is <arch><sub>-<vendor>-<sys>-<abi>. Run rustc --print target-list for a list of supported targets.

This may also be specified with the build.target config value.
--release: Build optimized artifacts with the release profile. See the PROFILES section for details on how this affects profile selection.

Output Options

--target-dir DIRECTORY: Directory for all generated artifacts and intermediate files. May also be specified with the CARGO_TARGET_DIR environment variable, or the build.target-dir config value. Defaults to target in the root of the workspace.

Display Options

-v

--verbose

Use verbose output. May be specified twice for "very verbose" output which includes extra output such as dependency warnings and build script output. May also be specified with the term.verbose config value.

-q

--quiet

No output printed to stdout.

--color WHEN

Control when colored output is used. Valid values:

auto (default): Automatically detect if color support is available on the terminal.
always: Always display colors.
never: Never display colors.

May also be specified with the term.color config value.

--message-format FMT

The output format for diagnostic messages. Valid values:

human (default): Display in a human-readable text format.
json: Emit JSON messages to stdout.
short: Emit shorter, human-readable text messages.

Manifest Options

--manifest-path PATH: Path to the Cargo.toml file. By default, Cargo searches in the current directory or any parent directory for the Cargo.toml file.
--frozen
--locked: Either of these flags requires that the Cargo.lock file is up-to-date. If the lock file is missing, or it needs to be updated, Cargo will exit with an error. The --frozen flag also prevents Cargo from attempting to access the network to determine if it is out-of-date.

These may be used in environments where you want to assert that the Cargo.lock file is up-to-date (such as a CI build) or want to avoid network access.
--offline: Prevents Cargo from accessing the network for any reason. Without this flag, Cargo will stop with an error if it needs to access the network and the network is not available. With this flag, Cargo will attempt to proceed without the network if possible.

Beware that this may result in different dependency resolution than online mode. Cargo will restrict itself to crates that are downloaded locally, even if there might be a newer version as indicated in the local copy of the index. See the cargo-fetch(1) command to download dependencies before going offline.

May also be specified with the net.offline config value.

Common Options

-h
--help: Prints help information.
-Z FLAG…: Unstable (nightly-only) flags to Cargo. Run cargo -Z help for details.

Miscellaneous Options

-j N
--jobs N: Number of parallel jobs to run. May also be specified with the build.jobs config value. Defaults to the number of CPUs.

PROFILES

Profiles may be used to configure compiler options such as optimization levels and debug settings. See the reference for more details.

Profile selection depends on the target and crate being built. By default the dev or test profiles are used. If the --release flag is given, then the release or bench profiles are used.

Target Default Profile --release Profile

Target	Default Profile	`--release` Profile
lib, bin, example	`dev`	`release`
test, bench, or any target in "test" or "bench" mode	`test`	`bench`

lib, bin, example

dev

release

test, bench, or any target
in "test" or "bench" mode

test

bench

Dependencies use the dev/release profiles.

ENVIRONMENT

See the reference for details on environment variables that Cargo reads.

Exit Status

0: Cargo succeeded.
101: Cargo failed to complete.

EXAMPLES

Check if your package (not including dependencies) uses unsafe code:
```
cargo rustc --lib -- -D unsafe-code
```
Try an experimental flag on the nightly compiler, such as this which prints the size of every type:
```
cargo rustc --lib -- -Z print-type-sizes
```

The Cargo Book

cargo rustc