Function configure_from_path

python3-sys/build.rs:339–404

Deduce configuration from the 'python' in the current PATH and print cargo vars to stdout. Note that if the python doesn't satisfy expected_version, this will error.

(expected_version: &PythonVersion)

///
/// Note that if the python doesn't satisfy expected_version, this will error.
fn configure_from_path(expected_version: &PythonVersion) -> Result<String, String> {
    let (interpreter_version, interpreter_path, lines) =
        find_interpreter_and_get_config(expected_version)?;
    let libpath: &str = &lines[0];
    let enable_shared: &str = &lines[1];
    let ld_version: &str = &lines[2];
    let exec_prefix: &str = &lines[3];

    let is_extension_module = watched_var_os("CARGO_FEATURE_EXTENSION_MODULE").is_some();
    let mut link_mode_default = watched_var_os("CARGO_FEATURE_LINK_MODE_DEFAULT").is_some();
    let link_mode_unresolved_static =
        watched_var_os("CARGO_FEATURE_LINK_MODE_UNRESOLVED_STATIC").is_some();

    if link_mode_default && link_mode_unresolved_static {
        return Err(
            "link-mode-default and link-mode-unresolved-static are mutually exclusive".to_owned(),
        );
    }

    if !link_mode_default && !link_mode_unresolved_static {
        link_mode_default = true;
    }

    if link_mode_default {
        if !is_extension_module || cfg!(target_os = "windows") {
            println!(
                "{}",
                get_rustc_link_lib(&interpreter_version, ld_version, enable_shared == "1").unwrap()
            );
            if libpath != "None" {
                println!("cargo:rustc-link-search=native={}", libpath);
            } else if cfg!(target_os = "windows") {
                println!("cargo:rustc-link-search=native={}\\libs", exec_prefix);
            }
        }
    } else if link_mode_unresolved_static && cfg!(target_os = "windows") {
        // static-nobundle requires a Nightly rustc up to at least
        // Rust 1.39 (https://github.com/rust-lang/rust/issues/37403).
        //
        // We need to use static linking on Windows to prevent symbol
        // name mangling. Otherwise Rust will prefix extern {} symbols
        // with __imp_. But if we used normal "static," we need a
        // pythonXY.lib at build time to package into the rlib.
        //
        // static-nobundle removes the build-time library requirement,
        // allowing a downstream consumer to provide the pythonXY library.
        println!("cargo:rustc-link-lib=static-nobundle=pythonXY");
    }

    if let PythonVersion {
        major: 3,
        minor: some_minor,
    } = interpreter_version
    {
        if watched_var_os("CARGO_FEATURE_PEP_384").is_some() {
            println!("cargo:rustc-cfg=Py_LIMITED_API");
        }
        if let Some(minor) = some_minor {