CARGO-RUSTC(1)

📦 version 1.92.0, in ubuntu resolute

cargo-rustc 💅

okay bestie, welcome to the cargo-rustc(1) manual page — General Commands Manual energy, but make it cute 🎀

✨ NAME ✨

cargo-rustc — compile the current package, and pass extra options to the compiler 🦋

✨ SYNOPSIS ✨

cargo rustc [options] [-- args]

✨ DESCRIPTION ✨

so here's the vibe: the target you picked for the current package (or the package you named with -p if you did that) gets compiled, and all of its dependencies come along for the ride too. 🫶

The args you specify? Those get passed to the final compiler invocation, not to any of the dependencies. Important distinction, no cap. But heads up — the compiler still unconditionally receives arguments like -L, --extern, and --crate-type no matter what, and your specified args just get added on top of the compiler invocation. ✨

For the docs on rustc flags, go look at <https://doc.rust-lang.org/rustc/index.html>.

🚨 the way that this command has a rule: it requires that only one target is being compiled when you provide additional arguments. If more than one target is available for the current package, you must use the filters --lib, --bin, etc. to select which target gets compiled. one target, bestie. that's the law. 💅

If you wanna pass flags to all the compiler processes spawned by Cargo, use the RUSTFLAGS environment variable <https://doc.rust-lang.org/cargo/reference/environment-variables.html> or the build.rustflags config value <https://doc.rust-lang.org/cargo/reference/config.html>. that's the move for whole-project flag vibes. 🌈

✨ OPTIONS ✨

🎀 Package Selection

By default, the package in the current working directory is selected. The -p flag lets you 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 you give no target selection options at all, cargo rustc will build all binary and library targets of the selected package. iconic default behavior honestly.

Binary targets are automatically built if there's an integration test or benchmark being selected to build. This lets an integration test execute the binary to exercise and test its behavior. The CARGO_BIN_EXE_<name> environment variable <https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates> is set when the integration test is built, so it can use the env macro <https://doc.rust-lang.org/std/macro.env.html> to locate the executable. 🧚

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 []. BUT — to avoid your shell accidentally expanding glob patterns before Cargo handles them, you must use single quotes or double quotes around each glob pattern. your shell is out here doing too much, protect the glob!! 😭

--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 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 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. literally all of them, slay. 🔥

🎀 Feature Selection

The feature flags let you control which features are enabled. When you give no feature options, the default feature is activated for every selected package. ✨

See the features documentation <https://doc.rust-lang.org/cargo/reference/features.html#command-line-feature-options> for more details.

-F features, --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 specified target architecture. Flag may be specified multiple times. The default is the host architecture. The general format of the triple is <arch><sub>-<vendor>-<sys>-<abi>. 🌸

Possible values:

Any supported target in rustc --print target-list.
"host-tuple", which will internally be substituted by the host's target. This can be particularly useful if you're cross-compiling some crates, and don't want to specify your host's machine as a target (for instance, an xtask in a shared project that may be worked on by many hosts). 🫶
A path to a custom target specification. See Custom Target Lookup Path <https://doc.rust-lang.org/rustc/targets/custom.html#custom-target-lookup-path> for more information.

This may also be specified with the build.target config value <https://doc.rust-lang.org/cargo/reference/config.html>.

💀 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 <https://doc.rust-lang.org/cargo/reference/build-cache.html> documentation for more details. different directory, different vibe, just so you know.

-r, --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 <https://doc.rust-lang.org/rustc/tests/index.html> for more detail.
bench — builds in the same was as the cargo-bench(1) command, similar to the test profile. (yes bestie, "was" is what the original says, i'm not fixing it, that's the text 💅)

See the reference <https://doc.rust-lang.org/cargo/reference/profiles.html> for more details on profiles.

--timings=fmts — output information how long each compilation takes, and track concurrency information over time. Accepts an optional comma-separated list of output formats; --timings without an argument will default to --timings=html. Specifying an output format (rather than the default) is unstable and requires -Zunstable-options. Valid output formats:
- html (unstable, requires -Zunstable-options): write a human-readable file cargo-timing.html to the target/cargo-timings directory with a report of the compilation. Also write a report to the same directory with a timestamp in the filename if you want to look at older runs. HTML output is suitable for human consumption only, and does not provide machine-readable timing data. 📊
- json (unstable, requires -Zunstable-options): emit machine-readable JSON information about timing information.
--crate-type crate-type — build for the given crate type. This flag accepts a comma-separated list of 1 or more crate types, of which the allowed values are the same as crate-type field in the manifest for configuring a Cargo target. See crate-type field <https://doc.rust-lang.org/cargo/reference/cargo-targets.html#the-crate-type-field> for possible values. 🎀

If the manifest contains a list, and --crate-type is provided, the command-line argument value will override what is in the manifest.

⭐ This flag only works when building a lib or example library target. no exceptions bestie.

🎀 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 <https://doc.rust-lang.org/cargo/reference/config.html>. 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 <https://doc.rust-lang.org/cargo/reference/config.html>. double it and it gets ✨spicy✨
-q, --quiet — do not print cargo log messages. May also be specified with the term.quiet config value <https://doc.rust-lang.org/cargo/reference/config.html>. shhh 🤫
--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 <https://doc.rust-lang.org/cargo/reference/config.html>.

--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 <https://doc.rust-lang.org/cargo/reference/external-tools.html#json-messages> for more details. Conflicts with human and short.
json-diagnostic-short — okay so this one makes sure the rendered field of JSON messages contains the “short” rendering from rustc. Cannot be used with human or short. 💅
json-diagnostic-rendered-ansi — this one makes the rendered field of JSON messages contain embedded ANSI color codes for respecting rustc’s default color scheme. Cannot be used with human or short. ✨
json-render-diagnostics — tells Cargo to not include rustc diagnostics 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. no cap.

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.
--ignore-rust-version — ignore rust-version specification in packages. periodt.
--locked — asserts that the exact same dependencies and versions are used as when the existing Cargo.lock file was originally generated. Cargo will exit with an error when either of the following scenarios arises:
- The lock file is missing.
- Cargo attempted to change the lock file due to a different dependency resolution.

It may be used in environments where deterministic builds are desired, such as in CI pipelines.

--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 <https://doc.rust-lang.org/cargo/reference/config.html>.

--frozen — equivalent to specifying both --locked and --offline.
--lockfile-path PATH — changes the path of the lockfile from the default (<workspace_root>/Cargo.lock) to PATH. PATH must end with Cargo.lock (e.g. --lockfile-path /tmp/temporary-lockfile/Cargo.lock). Note that providing --lockfile-path will ignore existing lockfile at the default path, and instead will either use the lockfile from PATH, or write a new lockfile into the provided PATH if it doesn’t exist. This flag can be used to run most commands in read-only directories, writing lockfile into the provided PATH.

This option is only available on the nightly channel <https://doc.rust-lang.org/book/appendix-07-nightly-rust.html> and requires the -Z unstable-options flag to enable (see #14421 <https://github.com/rust-lang/cargo/issues/14421>).

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 <https://rust-lang.github.io/rustup/overrides.html> for more information about how toolchain overrides work.
--config KEY=VALUE or PATH — overrides a Cargo configuration value. The argument should be in TOML syntax of KEY=VALUE, or provided as a path to an extra configuration file. This flag may be specified multiple times. See the command-line overrides section <https://doc.rust-lang.org/cargo/reference/config.html#command-line-overrides> for more information.
-C PATH — changes the current working directory before executing any specified operations. This affects things like where cargo looks by default for the project manifest (Cargo.toml), as well as the directories searched for discovering .cargo/config.toml, for example. This option must appear before the command name, for example cargo -C path/to/my-project build.

This option is only available on the nightly channel <https://doc.rust-lang.org/book/appendix-07-nightly-rust.html> and requires the -Z unstable-options flag to enable (see #10098 <https://github.com/rust-lang/cargo/issues/10098>).

-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 <https://doc.rust-lang.org/cargo/reference/config.html>. Defaults to the number of logical CPUs. If negative, it sets the maximum number of parallel jobs to the number of logical CPUs plus provided value. If a string default is provided, it sets the value back to defaults. Should not be 0.
--keep-going — build as many crates in the dependency graph as possible, rather than aborting the build on the first one that fails to build.

For example if the current package depends on dependencies fails and works, one of which fails to build, cargo rustc -j1 may or may not build the one that succeeds (depending on which one of the two builds Cargo picked to run first), whereas cargo rustc -j1 --keep-going would definitely run both builds, even if the one run first fails.

--future-incompat-report — displays a future-incompat report for any future-incompatible warnings produced during execution of this command.

See cargo-report(1).

ENVIRONMENT 🌸

See the reference <https://doc.rust-lang.org/cargo/reference/environment-variables.html> 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

Override crate-type field in Cargo.toml with command-line option:

cargo rustc --lib --crate-type lib,cdylib