Crate rustflags

  

Parser for CARGO_ENCODED_RUSTFLAGS.

This is one of the environment variables provided by Cargo to build scripts. It synthesizes several sources of flags affecting Cargo’s rustc invocations that build scripts might care about:

• Flags passed via the RUSTFLAGS environment variable,
• Cargo config entries under target.<triple>.rustflags and target.<cfg>.rustflags and build.rustflags, including from the project-specific Cargo config file and the Cargo config in the user’s CARGO_HOME.

If a build script needs to make some rustc invocations, or needs to characterize aspects of the upcoming rustc invocation, it likely needs these flags.

Example

This build script uses the cmake crate to compile some C code, and must configure it with a particular C preprocessor #define if the Rust build is being performed with sanitizers.

// build.rs

use rustflags::Flag;
use std::env;
use std::path::PathBuf;

fn main() {
    let manifest_dir = PathBuf::from(env::var_os("CARGO_MANIFEST_DIR").unwrap());
    let lib_source_dir = manifest_dir.join("lib");
    assert!(lib_source_dir.join("CMakeLists.txt").exists());

    let mut builder = cmake::Config::new(lib_source_dir);

    // Look for -Zsanitizer=address
    for flag in rustflags::from_env() {
        if matches!(flag, Flag::Z(z) if z == "sanitizer=address") {
            builder.define("ENABLE_SANITIZERS", "ON");
            builder.define("SANITIZERS", "address");
            break;
        }
    }

    builder.build();
}

Structs

RustFlags

Iterator of rustc flags

Enums

Color

Argument of --color

CrateType

Argument of --crate-type

Emit

Argument of --emit

ErrorFormat

Argument of --error-format

Flag

One flag recognized by rustc

LibraryKind

Argument of -L

LinkKind

Argument of -l

LinkModifier

Argument of -l

LinkModifierPrefix

Argument of -l

LintLevel

Argument of --cap-lints

Functions

from_encoded

Parse flags from a string separated with ASCII unit separator (‘\x1f’).

from_env

Parse flags from CARGO_ENCODED_RUSTFLAGS environment variable.