CARGO-RUSTC(1)

📦 version 1.77.2, in ubuntu jammy, ubuntu noble

✨ CARGO-RUSTC(1) ✨

General Commands Manual — okay so bestie, we're in the group chat of Unix man pages, and this one is cargo-rustc. It compiles the current package and passes extra options to the compiler. 💅

🌸 NAME 🌸

cargo-rustc — bestie, this compiles the current package and slides extra options straight to the compiler. No cap.

🎀 SYNOPSIS 🎀

cargo rustc [options] [-- args]

🦋 DESCRIPTION 🦋

Okay so here's the vibe: the specified target for the current package — or the package you picked with -p if you provided it — gets compiled along with all of its dependencies. The args you specify will all be passed to the final compiler invocation, not to any of the dependencies. Important: the compiler will still unconditionally receive arguments such as -L, --extern, and --crate-type, and your specified args are simply added to the compiler invocation. It's giving additive, not replacing. ✨

Need the docs on rustc flags? They live at https://doc.rust-lang.org/rustc/index.html.

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. So like, pick a lane bestie. 🎀

To pass flags to all 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.

👑 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. Slay.

  • -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. Iconic.

Binary targets are automatically built if there is an integration test or benchmark being selected to build. This allows an integration test to 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 that it can use the env macro https://doc.rust-lang.org/std/macro.env.html to locate the executable. Cute, right? 💖

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. No cap, quote your globs. 🫶

  • --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. Periodt.

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 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 flag may be specified multiple times.

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/guide/build-cache.html documentation for more details.

  • -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:

See the reference https://doc.rust-lang.org/cargo/reference/profiles.html 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.
  • --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.

📁 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.
  • -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.
  • --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: 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 — tells Cargo not to shove rustc diagnostics into the JSON messages it prints; instead Cargo itself renders the JSON diagnostics that rustc hands over. Cargo's own JSON diagnostics — plus the ones coming from rustc — still get emitted either way. 💅 Cannot be used with human or short. Pick a lane bestie.

💖 Manifest Options 💖

  • --manifest-path path — the path to the Cargo.toml file. By default Cargo goes looking for Cargo.toml in the current directory, and if it's not there, it keeps walking up through the parent directories. 🦋
  • --frozen, --locked — either one of these flags demands that the Cargo.lock file is up-to-date. If the lock file is missing, or it needs updating, Cargo just ✨ exits with an error ✨. The --frozen flag additionally stops Cargo from trying to touch the network to figure out if it's out-of-date.

These are for environments where you want to assert that Cargo.lock is up-to-date (like a CI build, queen of consistency 👑) or where you want to avoid network access entirely.

  • --offline — prevents Cargo from accessing the network for any reason. Without this flag, Cargo will stop with an error if it needs the network and the network isn't there. With this flag, Cargo will attempt to proceed without the network if it possibly can.
Beware that this may result in different dependency resolution than online mode. Cargo restricts 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>.

🌈 Common Options 🌈

  • +toolchain — if Cargo was installed with rustup, and the first argument to cargo starts with +, it gets interpreted as a rustup toolchain name (like +stable or +nightly). See the rustup documentation <https://rust-lang.github.io/rustup/overrides.html> for more info on 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 given 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. ✨
  • -C PATH — changes the current working directory before executing any specified operations. This affects stuff like where cargo looks by default for the project manifest (Cargo.toml), and also the directories it searches when 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. the way that this is the most underrated flag fr fr 🫶
  • -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 the 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. main character energy: it does not let one flop end the whole show 💅

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. slay. ✨
  • 101: Cargo failed to complete. 💀

🎀 EXAMPLES 🎀

  1. Check if your package (not including dependencies) uses unsafe code:
cargo rustc --lib -- -D unsafe-code
  1. 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
  1. Override crate-type field in Cargo.toml with command-line option:
cargo rustc --lib --crate-type lib,cdylib

⭐ SEE ALSO ⭐

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

and that's the whole page bestie, we ate and left no crumbs 🔥 this was the cargo-rustc(1) man page, source and version as shipped in the Cargo docs, dated with the page's own footer timestamp — go forth and cargo rustc responsibly, ily, bye 💖🌈👑

📦 where this page comes from