How to use the command "cargo rustc" (with examples)
“Cargo rustc” is a command-line tool in Rust that allows you to compile a Rust project. It works similarly to the “cargo build” command, but provides the flexibility to pass extra options to the Rust compiler (“rustc”).
Use case 1: Build the package and pass options to rustc
Code:
cargo rustc -- rustc_options
Motivation: This use case is useful when you want to pass specific options to the Rust compiler while building your project. For example, you may want to enable specific optimizations or provide custom flags to the compiler.
Explanation:
cargo rustc: This is the base command to compile the Rust package.--: This separator is used to indicate the end of the cargo-specific options and the beginning of the rustc-specific options.rustc_options: These are the additional options that will be passed directly to the Rust compiler (“rustc”).
Example output: Compiling your Rust package with specific options using this command would result in the build process considering the passed “rustc_options” during compilation.
Use case 2: Build artifacts in release mode, with optimizations
Code:
cargo rustc --release
Motivation: In certain scenarios, you may want to build your Rust package with optimizations to improve the performance. Building in release mode enables various optimizations, such as inlining function calls and removing debug symbols.
Explanation:
cargo rustc: The base command to compile the Rust package.--release: This flag tells Cargo to build the package in release mode, enabling optimizations and producing smaller executables.
Example output: Building the package in release mode with optimizations would result in faster and more efficient code execution, along with smaller artifact sizes.
Use case 3: Compile with architecture-specific optimizations for the current CPU
Code:
cargo rustc --release -- -C target-cpu=native
Motivation: Applying architecture-specific optimizations can significantly improve the performance of your compiled code. This use case allows you to compile your Rust package with optimizations tailored to the CPU architecture of the system where the compilation is performed.
Explanation:
cargo rustc: The base command to compile the Rust package.--release: Flag to build the package in release mode with optimizations.--: Separator between cargo-specific options and the rustc-specific options.-C target-cpu=native: This rustc option tells the compiler to generate code optimized specifically for the CPU architecture of the machine on which the compilation is being performed.
Example output: Compiling with architecture-specific optimizations would result in the Rust package being tailored to the CPU’s capabilities, potentially providing improved runtime performance.
Use case 4: Compile with speed optimizations
Code:
cargo rustc -- -C opt-level 1
Motivation: This use case allows you to control the level of optimization applied to your Rust code during compilation. Choosing the appropriate optimization level can strike a balance between code size and execution speed.
Explanation:
cargo rustc: The base command to compile the Rust package.--: Separator between cargo-specific options and rustc-specific options.-C opt-level 1: This rustc option selects the optimization level to be used during compilation. Valid values are 1, 2, or 3, with higher values providing more aggressive optimization.
Example output: Compiling with speed optimizations set to level 1 would result in a smaller executable size compared to higher optimization levels, sacrificing some potential runtime performance improvements.
Use case 5: Compile with size optimizations
Code:
cargo rustc -- -C opt-level z
Motivation: Choosing size optimization can be beneficial when you want to reduce the size of the compiled code at the expense of potential performance improvements. It is particularly useful for embedded systems or situations with limited resources.
Explanation:
cargo rustc: The base command to compile the Rust package.--: Separator between cargo-specific options and rustc-specific options.-C opt-level z: This rustc option configures the compiler to perform size optimizations, potentially resulting in smaller binary sizes. The ‘z’ flag also disables loop vectorization.
Example output: Compiling with size optimizations would generate a smaller binary size, which can be advantageous in resource-constrained environments.
Use case 6: Check if your package uses unsafe code
Code:
cargo rustc --lib -- -D unsafe-code
Motivation: Ensuring the safety of Rust code is important. By using this use case, you can check if your package contains any unsafe code, allowing you to review and analyze potential safety concerns.
Explanation:
cargo rustc: The base command to compile the Rust package.--lib: This flag instructs Cargo to build the package’s library only, excluding the binary targets.--: Separator between cargo-specific options and rustc-specific options.-D unsafe-code: This rustc option enables additional linting to check for unsafe code usage.
Example output: Running the command would trigger additional linting during the compilation process, highlighting any instances of unsafe code in your package.
Use case 7: Build a specific package
Code:
cargo rustc --package package
Motivation: If you have a Cargo workspace with multiple packages, specifying a particular package allows you to compile only the Rust code associated with that package. This is useful when you want to save time by avoiding the compilation of all packages.
Explanation:
cargo rustc: The base command to compile the Rust package.--package package: This flag specifies the package to be built, identified by its name.
Example output: Running this command would compile only the specified package, excluding any other packages within the Cargo workspace.
Use case 8: Build only the specified binary
Code:
cargo --bin name
Motivation: When working with a Rust project that contains multiple binaries, you may want to build only a specific one instead of all the binaries. This use case allows you to compile and build a single binary from the project.
Explanation:
cargo --bin: This flag specifies that you only want to build the binary target(s).name: This argument represents the name of the binary you want to build.
Example output: Executing this command would compile and build the specified binary, resulting in the creation of an executable for that specific binary.
