cargo-rustc(1)

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.

Note that --bin, --example, --test and --bench flags also support common Unix glob patterns like *, ? and []. However, to avoid your shell accidentally expanding glob patterns before Cargo handles them, you must use single quotes or double quotes around each glob pattern.

--lib
Build the package's library.
--bin name...
Build the specified binary. This flag may be specified multiple times and supports common Unix glob patterns.
--bins
Build all binary targets.
--example name...
Build the specified example. This flag may be specified multiple times and supports common Unix glob patterns.
--examples
Build all example targets.
--test name...
Build the specified integration test. This flag may be specified multiple times and supports common Unix glob patterns.
--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 and supports common Unix glob patterns.
--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

The feature flags allow you to control which features are enabled. When no feature options are given, the default feature is activated for every selected package.

See the features documentation for more details.

--features features
Space or comma separated list of features to activate. Features of workspace members may be enabled with package-name/feature-name syntax. This flag may be specified multiple times, which enables all specified features.
--all-features
Activate all available features of all selected packages.
--no-default-features
Do not activate the default feature of the selected packages.

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.

Note that specifying this flag makes Cargo run in a different mode where the target artifacts are placed in a separate directory. See the build cache documentation for more details.

--release
Build optimized artifacts with the release profile. See also the --profile option for choosing a specific profile by name.
--profile name
Build with the given profile.

The rustc subcommand will treat the following named profiles with special behaviors:

  • check — Builds in the same way as the cargo-check(1) command with the dev profile.
  • test — Builds in the same way as the cargo-test(1) command, enabling building in test mode which will enable tests and enable the test cfg option. See rustc tests for more detail.
  • bench — Builds in the same was as the cargo-bench(1) command, similar to the test profile.

See the the reference for more details on profiles.

--ignore-rust-version
Build the target even if the selected Rust compiler is older than the required Rust version as configured in the project's rust-version field.

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. Can be specified multiple times and consists of comma-separated values. Valid values:

  • human (default): Display in a human-readable text format. Conflicts with short and json.
  • short: Emit shorter, human-readable text messages. Conflicts with human and json.
  • json: Emit JSON messages to stdout. See the reference for more details. Conflicts with human and short.
  • json-diagnostic-short: Ensure the rendered field of JSON messages contains the "short" rendering from rustc. Cannot be used with human or short.
  • json-diagnostic-rendered-ansi: Ensure the rendered field of JSON messages contains embedded ANSI color codes for respecting rustc's default color scheme. Cannot be used with human or short.
  • json-render-diagnostics: Instruct Cargo to not include rustc diagnostics in in JSON messages printed, but instead Cargo itself should render the JSON diagnostics coming from rustc. Cargo's own JSON diagnostics and others coming from rustc are still emitted. Cannot be used with human or short.

Manifest Options

--manifest-path path
Path to the Cargo.toml file. By default, Cargo searches for the Cargo.toml file in the current directory or any parent directory.
--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

+toolchain
If Cargo has been installed with rustup, and the first argument to cargo begins with +, it will be interpreted as a rustup toolchain name (such as +stable or +nightly). See the rustup documentation for more information about how toolchain overrides work.
-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.

ENVIRONMENT

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

EXIT STATUS

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

EXAMPLES

  1. Check if your package (not including dependencies) uses unsafe code:

    cargo rustc --lib -- -D unsafe-code

  2. 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

SEE ALSO

cargo(1), cargo-build(1), rustc(1)