Function main

build.rs:8–198

()

const ASM_PATH: &str = "src/backend/linux_raw/arch";

fn main() {
    // Don't rerun this on changes other than build.rs, as we only depend on
    // the rustc version.
    println!("cargo:rerun-if-changed=build.rs");

    // Gather target information.
    let arch = var("CARGO_CFG_TARGET_ARCH").unwrap();
    let env = var("CARGO_CFG_TARGET_ENV").unwrap();
    let abi = var("CARGO_CFG_TARGET_ABI");
    let inline_asm_name = format!("{}/{}.rs", ASM_PATH, arch);
    let inline_asm_name_present = std::fs::metadata(inline_asm_name).is_ok();
    let os = var("CARGO_CFG_TARGET_OS").unwrap();
    let pointer_width = var("CARGO_CFG_TARGET_POINTER_WIDTH").unwrap();
    let endian = var("CARGO_CFG_TARGET_ENDIAN").unwrap();

    // Check for special target variants.
    let is_x32 = arch == "x86_64" && pointer_width == "32";
    let is_arm64_ilp32 = arch == "aarch64" && pointer_width == "32";
    let is_powerpc64be = arch == "powerpc64" && endian == "big";
    let is_mipseb = (arch == "mips" || arch == "mips32r6") && endian == "big";
    let is_mips64eb = arch.contains("mips64") && endian == "big";
    let is_unsupported_abi = is_x32 || is_arm64_ilp32 || is_powerpc64be || is_mipseb || is_mips64eb;

    // Check for `--features=use-libc`. This allows crate users to enable the
    // libc backend.
    let feature_use_libc = var("CARGO_FEATURE_USE_LIBC").is_ok();

    // Check for `RUSTFLAGS=--cfg=rustix_use_libc`. This allows end users to
    // enable the libc backend even if rustix is depended on transitively.
    let cfg_use_libc = var("CARGO_CFG_RUSTIX_USE_LIBC").is_ok();

    // Check for `RUSTFLAGS=--cfg=rustix_no_linux_raw`. This allows Linux users to
    // enable the libc backend without the linux raw dependency.
    let cfg_no_linux_raw = var("CARGO_CFG_RUSTIX_NO_LINUX_RAW").is_ok();

    // Check for `--features=rustc-dep-of-std`.
    let rustc_dep_of_std = var("CARGO_FEATURE_RUSTC_DEP_OF_STD").is_ok();

    // Check for eg. `RUSTFLAGS=--cfg=rustix_use_experimental_features`. This
    // is a rustc flag rather than a cargo feature flag because it's
    // experimental and not something we want accidentally enabled via
    // `--all-features`.
    let rustix_use_experimental_features =
        var("CARGO_CFG_RUSTIX_USE_EXPERIMENTAL_FEATURES").is_ok();

    // Check for eg. `RUSTFLAGS=--cfg=rustix_use_experimental_asm`. This is a
    // rustc flag rather than a cargo feature flag because it's experimental
    // and not something we want accidentally enabled via `--all-features`.
    let rustix_use_experimental_asm = var("CARGO_CFG_RUSTIX_USE_EXPERIMENTAL_ASM").is_ok();

    // Miri doesn't support inline asm, and has builtin support for recognizing
    // libc FFI calls, so if we're running under miri, use the libc backend.
    let miri = var("CARGO_CFG_MIRI").is_ok();

    // If experimental features are enabled, auto-detect and use available
    // features.
    if rustc_dep_of_std {
        use_feature("rustc_attrs");