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.