Rollup merge of #92297 - bjorn3:smaller_bootstrap, r=Mark-Simulacrum

Reduce compile time of rustbuild

Best reviewed commit by commit. The `ignore` crate and it's dependencies are probably responsible for the majority of the compile time after this PR.

cc `@jyn514` as you got a couple of open rustbuild PR.

Cargo.lock

@@ -175,9 +175,7 @@ dependencies = [
  "filetime",
  "getopts",
  "ignore",
- "lazy_static",
  "libc",
- "merge",
  "num_cpus",
  "once_cell",
  "opener",
@@ -2221,28 +2219,6 @@ dependencies = [
  "autocfg",
 ]
 
-[[package]]
-name = "merge"
-version = "0.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "10bbef93abb1da61525bbc45eeaff6473a41907d19f8f9aa5168d214e10693e9"
-dependencies = [
- "merge_derive",
- "num-traits",
-]
-
-[[package]]
-name = "merge_derive"
-version = "0.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "209d075476da2e63b4b29e72a2ef627b840589588e71400a25e3565c4f849d07"
-dependencies = [
- "proc-macro-error",
- "proc-macro2",
- "quote",
- "syn",
-]
-
 [[package]]
 name = "minifier"
 version = "0.0.41"

src/bootstrap/Cargo.toml

@@ -44,11 +44,9 @@ libc = "0.2"
 serde = { version = "1.0.8", features = ["derive"] }
 serde_json = "1.0.2"
 toml = "0.5"
-lazy_static = "1.3.0"
 time = "0.1"
 ignore = "0.4.10"
 opener = "0.5"
-merge = "0.1.0"
 once_cell = "1.7.2"
 
 [target.'cfg(windows)'.dependencies.winapi]

src/bootstrap/bin/rustc.rs

@@ -15,6 +15,8 @@
 //! switching compilers for the bootstrap and for build scripts will probably
 //! never get replaced.
 
+include!("../dylib_util.rs");
+
 use std::env;
 use std::path::PathBuf;
 use std::process::{Child, Command};
@@ -50,11 +52,11 @@ fn main() {
 
     let rustc = env::var_os(rustc).unwrap_or_else(|| panic!("{:?} was not set", rustc));
     let libdir = env::var_os(libdir).unwrap_or_else(|| panic!("{:?} was not set", libdir));
-    let mut dylib_path = bootstrap::util::dylib_path();
+    let mut dylib_path = dylib_path();
     dylib_path.insert(0, PathBuf::from(&libdir));
 
     let mut cmd = Command::new(rustc);
-    cmd.args(&args).env(bootstrap::util::dylib_path_var(), env::join_paths(&dylib_path).unwrap());
+    cmd.args(&args).env(dylib_path_var(), env::join_paths(&dylib_path).unwrap());
 
     // Get the name of the crate we're compiling, if any.
     let crate_name =
@@ -161,7 +163,7 @@ fn main() {
         eprintln!(
             "{} command: {:?}={:?} {:?}",
             prefix,
-            bootstrap::util::dylib_path_var(),
+            dylib_path_var(),
             env::join_paths(&dylib_path).unwrap(),
             cmd,
         );

src/bootstrap/bin/rustdoc.rs

@@ -7,6 +7,8 @@
 use std::path::PathBuf;
 use std::process::Command;
 
+include!("../dylib_util.rs");
+
 fn main() {
     let args = env::args_os().skip(1).collect::<Vec<_>>();
     let rustdoc = env::var_os("RUSTDOC_REAL").expect("RUSTDOC_REAL was not set");
@@ -20,14 +22,14 @@ fn main() {
         Err(_) => 0,
     };
 
-    let mut dylib_path = bootstrap::util::dylib_path();
+    let mut dylib_path = dylib_path();
     dylib_path.insert(0, PathBuf::from(libdir.clone()));
 
     let mut cmd = Command::new(rustdoc);
     cmd.args(&args)
         .arg("--sysroot")
         .arg(&sysroot)
-        .env(bootstrap::util::dylib_path_var(), env::join_paths(&dylib_path).unwrap());
+        .env(dylib_path_var(), env::join_paths(&dylib_path).unwrap());
 
     // Force all crates compiled by this compiler to (a) be unstable and (b)
     // allow the `rustc_private` feature to link to other unstable crates
@@ -59,7 +61,7 @@ fn main() {
     if verbose > 1 {
         eprintln!(
             "rustdoc command: {:?}={:?} {:?}",
-            bootstrap::util::dylib_path_var(),
+            dylib_path_var(),
             env::join_paths(&dylib_path).unwrap(),
             cmd,
         );

src/bootstrap/builder.rs

@@ -351,7 +351,6 @@ pub enum Kind {
     Check,
     Clippy,
     Fix,
-    Format,
     Test,
     Bench,
     Dist,
@@ -399,7 +398,7 @@ fn get_step_descriptions(kind: Kind) -> Vec<StepDescription> {
                 native::Lld,
                 native::CrtBeginEnd
             ),
-            Kind::Check | Kind::Clippy { .. } | Kind::Fix | Kind::Format => describe!(
+            Kind::Check | Kind::Clippy { .. } | Kind::Fix => describe!(
                 check::Std,
                 check::Rustc,
                 check::Rustdoc,

src/bootstrap/cache.rs

@@ -13,7 +13,8 @@
 use std::path::{Path, PathBuf};
 use std::sync::Mutex;
 
-use lazy_static::lazy_static;
+// FIXME: replace with std::lazy after it gets stabilized and reaches beta
+use once_cell::sync::Lazy;
 
 use crate::builder::Step;
 
@@ -222,9 +223,7 @@ pub fn intern_path(&self, s: PathBuf) -> Interned<PathBuf> {
     }
 }
 
-lazy_static! {
-    pub static ref INTERNER: Interner = Interner::default();
-}
+pub static INTERNER: Lazy<Interner> = Lazy::new(Interner::default);
 
 /// This is essentially a `HashMap` which allows storing any type in its input and
 /// any type in its output. It is a write-once cache; values are never evicted,

src/bootstrap/config.rs

@@ -18,7 +18,6 @@
 use crate::flags::{Color, Flags};
 use crate::util::exe;
 use build_helper::t;
-use merge::Merge;
 use serde::Deserialize;
 
 macro_rules! check_ci_llvm {
@@ -334,6 +333,10 @@ struct TomlConfig {
     profile: Option<String>,
 }
 
+trait Merge {
+    fn merge(&mut self, other: Self);
+}
+
 impl Merge for TomlConfig {
     fn merge(
         &mut self,
@@ -357,105 +360,136 @@ fn do_merge<T: Merge>(x: &mut Option<T>, y: Option<T>) {
     }
 }
 
-/// TOML representation of various global build decisions.
-#[derive(Deserialize, Default, Clone, Merge)]
-#[serde(deny_unknown_fields, rename_all = "kebab-case")]
-struct Build {
-    build: Option<String>,
-    host: Option<Vec<String>>,
-    target: Option<Vec<String>>,
-    // This is ignored, the rust code always gets the build directory from the `BUILD_DIR` env variable
-    build_dir: Option<String>,
-    cargo: Option<String>,
-    rustc: Option<String>,
-    rustfmt: Option<PathBuf>,
-    docs: Option<bool>,
-    compiler_docs: Option<bool>,
-    docs_minification: Option<bool>,
-    submodules: Option<bool>,
-    fast_submodules: Option<bool>,
-    gdb: Option<String>,
-    nodejs: Option<String>,
-    npm: Option<String>,
-    python: Option<String>,
-    locked_deps: Option<bool>,
-    vendor: Option<bool>,
-    full_bootstrap: Option<bool>,
-    extended: Option<bool>,
-    tools: Option<HashSet<String>>,
-    verbose: Option<usize>,
-    sanitizers: Option<bool>,
-    profiler: Option<bool>,
-    cargo_native_static: Option<bool>,
-    low_priority: Option<bool>,
-    configure_args: Option<Vec<String>>,
-    local_rebuild: Option<bool>,
-    print_step_timings: Option<bool>,
-    print_step_rusage: Option<bool>,
-    check_stage: Option<u32>,
-    doc_stage: Option<u32>,
-    build_stage: Option<u32>,
-    test_stage: Option<u32>,
-    install_stage: Option<u32>,
-    dist_stage: Option<u32>,
-    bench_stage: Option<u32>,
-    patch_binaries_for_nix: Option<bool>,
+// We are using a decl macro instead of a derive proc macro here to reduce the compile time of
+// rustbuild.
+macro_rules! derive_merge {
+    ($(#[$attr:meta])* struct $name:ident {
+        $($field:ident: $field_ty:ty,)*
+    }) => {
+        $(#[$attr])*
+        struct $name {
+            $($field: $field_ty,)*
+        }
+
+        impl Merge for $name {
+            fn merge(&mut self, other: Self) {
+                $(
+                    if !self.$field.is_some() {
+                        self.$field = other.$field;
+                    }
+                )*
+            }
+        }
+    }
 }
 
-/// TOML representation of various global install decisions.
-#[derive(Deserialize, Default, Clone, Merge)]
-#[serde(deny_unknown_fields, rename_all = "kebab-case")]
-struct Install {
-    prefix: Option<String>,
-    sysconfdir: Option<String>,
-    docdir: Option<String>,
-    bindir: Option<String>,
-    libdir: Option<String>,
-    mandir: Option<String>,
-    datadir: Option<String>,
+derive_merge! {
+    /// TOML representation of various global build decisions.
+    #[derive(Deserialize, Default, Clone)]
+    #[serde(deny_unknown_fields, rename_all = "kebab-case")]
+    struct Build {
+        build: Option<String>,
+        host: Option<Vec<String>>,
+        target: Option<Vec<String>>,
+        // This is ignored, the rust code always gets the build directory from the `BUILD_DIR` env variable
+        build_dir: Option<String>,
+        cargo: Option<String>,
+        rustc: Option<String>,
+        rustfmt: Option<PathBuf>,
+        docs: Option<bool>,
+        compiler_docs: Option<bool>,
+        docs_minification: Option<bool>,
+        submodules: Option<bool>,
+        fast_submodules: Option<bool>,
+        gdb: Option<String>,
+        nodejs: Option<String>,
+        npm: Option<String>,
+        python: Option<String>,
+        locked_deps: Option<bool>,
+        vendor: Option<bool>,
+        full_bootstrap: Option<bool>,
+        extended: Option<bool>,
+        tools: Option<HashSet<String>>,
+        verbose: Option<usize>,
+        sanitizers: Option<bool>,
+        profiler: Option<bool>,
+        cargo_native_static: Option<bool>,
+        low_priority: Option<bool>,
+        configure_args: Option<Vec<String>>,
+        local_rebuild: Option<bool>,
+        print_step_timings: Option<bool>,
+        print_step_rusage: Option<bool>,
+        check_stage: Option<u32>,
+        doc_stage: Option<u32>,
+        build_stage: Option<u32>,
+        test_stage: Option<u32>,
+        install_stage: Option<u32>,
+        dist_stage: Option<u32>,
+        bench_stage: Option<u32>,
+        patch_binaries_for_nix: Option<bool>,
+    }
 }
 
-/// TOML representation of how the LLVM build is configured.
-#[derive(Deserialize, Default, Merge)]
-#[serde(deny_unknown_fields, rename_all = "kebab-case")]
-struct Llvm {
-    skip_rebuild: Option<bool>,
-    optimize: Option<bool>,
-    thin_lto: Option<bool>,
-    release_debuginfo: Option<bool>,
-    assertions: Option<bool>,
-    tests: Option<bool>,
-    plugins: Option<bool>,
-    ccache: Option<StringOrBool>,
-    version_check: Option<bool>,
-    static_libstdcpp: Option<bool>,
-    ninja: Option<bool>,
-    targets: Option<String>,
-    experimental_targets: Option<String>,
-    link_jobs: Option<u32>,
-    link_shared: Option<bool>,
-    version_suffix: Option<String>,
-    clang_cl: Option<String>,
-    cflags: Option<String>,
-    cxxflags: Option<String>,
-    ldflags: Option<String>,
-    use_libcxx: Option<bool>,
-    use_linker: Option<String>,
-    allow_old_toolchain: Option<bool>,
-    polly: Option<bool>,
-    clang: Option<bool>,
-    download_ci_llvm: Option<StringOrBool>,
+derive_merge! {
+    /// TOML representation of various global install decisions.
+    #[derive(Deserialize, Default, Clone)]
+    #[serde(deny_unknown_fields, rename_all = "kebab-case")]
+    struct Install {
+        prefix: Option<String>,
+        sysconfdir: Option<String>,
+        docdir: Option<String>,
+        bindir: Option<String>,
+        libdir: Option<String>,
+        mandir: Option<String>,
+        datadir: Option<String>,
+    }
 }
 
-#[derive(Deserialize, Default, Clone, Merge)]
-#[serde(deny_unknown_fields, rename_all = "kebab-case")]
-struct Dist {
-    sign_folder: Option<String>,
-    gpg_password_file: Option<String>,
-    upload_addr: Option<String>,
-    src_tarball: Option<bool>,
-    missing_tools: Option<bool>,
-    compression_formats: Option<Vec<String>>,
+derive_merge! {
+    /// TOML representation of how the LLVM build is configured.
+    #[derive(Deserialize, Default)]
+    #[serde(deny_unknown_fields, rename_all = "kebab-case")]
+    struct Llvm {
+        skip_rebuild: Option<bool>,
+        optimize: Option<bool>,
+        thin_lto: Option<bool>,
+        release_debuginfo: Option<bool>,
+        assertions: Option<bool>,
+        tests: Option<bool>,
+        plugins: Option<bool>,
+        ccache: Option<StringOrBool>,
+        version_check: Option<bool>,
+        static_libstdcpp: Option<bool>,
+        ninja: Option<bool>,
+        targets: Option<String>,
+        experimental_targets: Option<String>,
+        link_jobs: Option<u32>,
+        link_shared: Option<bool>,
+        version_suffix: Option<String>,
+        clang_cl: Option<String>,
+        cflags: Option<String>,
+        cxxflags: Option<String>,
+        ldflags: Option<String>,
+        use_libcxx: Option<bool>,
+        use_linker: Option<String>,
+        allow_old_toolchain: Option<bool>,
+        polly: Option<bool>,
+        clang: Option<bool>,
+        download_ci_llvm: Option<StringOrBool>,
+    }
+}
+
+derive_merge! {
+    #[derive(Deserialize, Default, Clone)]
+    #[serde(deny_unknown_fields, rename_all = "kebab-case")]
+    struct Dist {
+        sign_folder: Option<String>,
+        gpg_password_file: Option<String>,
+        upload_addr: Option<String>,
+        src_tarball: Option<bool>,
+        missing_tools: Option<bool>,
+        compression_formats: Option<Vec<String>>,
+    }
 }
 
 #[derive(Deserialize)]
@@ -471,80 +505,84 @@ fn default() -> StringOrBool {
     }
 }
 
-/// TOML representation of how the Rust build is configured.
-#[derive(Deserialize, Default, Merge)]
-#[serde(deny_unknown_fields, rename_all = "kebab-case")]
-struct Rust {
-    optimize: Option<bool>,
-    debug: Option<bool>,
-    codegen_units: Option<u32>,
-    codegen_units_std: Option<u32>,
-    debug_assertions: Option<bool>,
-    debug_assertions_std: Option<bool>,
-    overflow_checks: Option<bool>,
-    overflow_checks_std: Option<bool>,
-    debug_logging: Option<bool>,
-    debuginfo_level: Option<u32>,
-    debuginfo_level_rustc: Option<u32>,
-    debuginfo_level_std: Option<u32>,
-    debuginfo_level_tools: Option<u32>,
-    debuginfo_level_tests: Option<u32>,
-    run_dsymutil: Option<bool>,
-    backtrace: Option<bool>,
-    incremental: Option<bool>,
-    parallel_compiler: Option<bool>,
-    default_linker: Option<String>,
-    channel: Option<String>,
-    description: Option<String>,
-    musl_root: Option<String>,
-    rpath: Option<bool>,
-    verbose_tests: Option<bool>,
-    optimize_tests: Option<bool>,
-    codegen_tests: Option<bool>,
-    ignore_git: Option<bool>,
-    dist_src: Option<bool>,
-    save_toolstates: Option<String>,
-    codegen_backends: Option<Vec<String>>,
-    lld: Option<bool>,
-    use_lld: Option<bool>,
-    llvm_tools: Option<bool>,
-    deny_warnings: Option<bool>,
-    backtrace_on_ice: Option<bool>,
-    verify_llvm_ir: Option<bool>,
-    thin_lto_import_instr_limit: Option<u32>,
-    remap_debuginfo: Option<bool>,
-    jemalloc: Option<bool>,
-    test_compare_mode: Option<bool>,
-    llvm_libunwind: Option<String>,
-    control_flow_guard: Option<bool>,
-    new_symbol_mangling: Option<bool>,
-    profile_generate: Option<String>,
-    profile_use: Option<String>,
-    // ignored; this is set from an env var set by bootstrap.py
-    download_rustc: Option<StringOrBool>,
+derive_merge! {
+    /// TOML representation of how the Rust build is configured.
+    #[derive(Deserialize, Default)]
+    #[serde(deny_unknown_fields, rename_all = "kebab-case")]
+    struct Rust {
+        optimize: Option<bool>,
+        debug: Option<bool>,
+        codegen_units: Option<u32>,
+        codegen_units_std: Option<u32>,
+        debug_assertions: Option<bool>,
+        debug_assertions_std: Option<bool>,
+        overflow_checks: Option<bool>,
+        overflow_checks_std: Option<bool>,
+        debug_logging: Option<bool>,
+        debuginfo_level: Option<u32>,
+        debuginfo_level_rustc: Option<u32>,
+        debuginfo_level_std: Option<u32>,
+        debuginfo_level_tools: Option<u32>,
+        debuginfo_level_tests: Option<u32>,
+        run_dsymutil: Option<bool>,
+        backtrace: Option<bool>,
+        incremental: Option<bool>,
+        parallel_compiler: Option<bool>,
+        default_linker: Option<String>,
+        channel: Option<String>,
+        description: Option<String>,
+        musl_root: Option<String>,
+        rpath: Option<bool>,
+        verbose_tests: Option<bool>,
+        optimize_tests: Option<bool>,
+        codegen_tests: Option<bool>,
+        ignore_git: Option<bool>,
+        dist_src: Option<bool>,
+        save_toolstates: Option<String>,
+        codegen_backends: Option<Vec<String>>,
+        lld: Option<bool>,
+        use_lld: Option<bool>,
+        llvm_tools: Option<bool>,
+        deny_warnings: Option<bool>,
+        backtrace_on_ice: Option<bool>,
+        verify_llvm_ir: Option<bool>,
+        thin_lto_import_instr_limit: Option<u32>,
+        remap_debuginfo: Option<bool>,
+        jemalloc: Option<bool>,
+        test_compare_mode: Option<bool>,
+        llvm_libunwind: Option<String>,
+        control_flow_guard: Option<bool>,
+        new_symbol_mangling: Option<bool>,
+        profile_generate: Option<String>,
+        profile_use: Option<String>,
+        // ignored; this is set from an env var set by bootstrap.py
+        download_rustc: Option<StringOrBool>,
+    }
 }
 
-/// TOML representation of how each build target is configured.
-#[derive(Deserialize, Default, Merge)]
-#[serde(deny_unknown_fields, rename_all = "kebab-case")]
-struct TomlTarget {
-    cc: Option<String>,
-    cxx: Option<String>,
-    ar: Option<String>,
-    ranlib: Option<String>,
-    default_linker: Option<PathBuf>,
-    linker: Option<String>,
-    llvm_config: Option<String>,
-    llvm_filecheck: Option<String>,
-    android_ndk: Option<String>,
-    sanitizers: Option<bool>,
-    profiler: Option<bool>,
-    crt_static: Option<bool>,
-    musl_root: Option<String>,
-    musl_libdir: Option<String>,
-    wasi_root: Option<String>,
-    qemu_rootfs: Option<String>,
-    no_std: Option<bool>,
+derive_merge! {
+    /// TOML representation of how each build target is configured.
+    #[derive(Deserialize, Default)]
+    #[serde(deny_unknown_fields, rename_all = "kebab-case")]
+    struct TomlTarget {
+        cc: Option<String>,
+        cxx: Option<String>,
+        ar: Option<String>,
+        ranlib: Option<String>,
+        default_linker: Option<PathBuf>,
+        linker: Option<String>,
+        llvm_config: Option<String>,
+        llvm_filecheck: Option<String>,
+        android_ndk: Option<String>,
+        sanitizers: Option<bool>,
+        profiler: Option<bool>,
+        crt_static: Option<bool>,
+        musl_root: Option<String>,
+        musl_libdir: Option<String>,
+        wasi_root: Option<String>,
+        qemu_rootfs: Option<String>,
+        no_std: Option<bool>,
+    }
 }
 
 impl Config {
@@ -1111,10 +1149,6 @@ pub fn verbose(&self) -> bool {
         self.verbose > 0
     }
 
-    pub fn very_verbose(&self) -> bool {
-        self.verbose > 1
-    }
-
     pub fn sanitizers_enabled(&self, target: TargetSelection) -> bool {
         self.target_config.get(&target).map(|t| t.sanitizers).flatten().unwrap_or(self.sanitizers)
     }

src/bootstrap/dylib_util.rs

+// Various utilities for working with dylib paths.
+//
+// This file is meant to be included directly to avoid a dependency on the bootstrap library from
+// the rustc and rustdoc wrappers. This improves compilation time by reducing the linking time.
+
+/// Returns the environment variable which the dynamic library lookup path
+/// resides in for this platform.
+pub fn dylib_path_var() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "PATH"
+    } else if cfg!(target_os = "macos") {
+        "DYLD_LIBRARY_PATH"
+    } else if cfg!(target_os = "haiku") {
+        "LIBRARY_PATH"
+    } else {
+        "LD_LIBRARY_PATH"
+    }
+}
+
+/// Parses the `dylib_path_var()` environment variable, returning a list of
+/// paths that are members of this lookup path.
+pub fn dylib_path() -> Vec<PathBuf> {
+    let var = match env::var_os(dylib_path_var()) {
+        Some(v) => v,
+        None => return vec![],
+    };
+    env::split_paths(&var).collect()
+}

src/bootstrap/lib.rs

@@ -110,7 +110,6 @@
 use std::io::{Read, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
 use std::process::{self, Command};
-use std::slice;
 use std::str;
 
 #[cfg(unix)]
@@ -472,10 +471,6 @@ pub fn new(config: Config) -> Build {
         build
     }
 
-    pub fn build_triple(&self) -> &[Interned<String>] {
-        slice::from_ref(&self.build.triple)
-    }
-
     // modified from `check_submodule` and `update_submodule` in bootstrap.py
     /// Given a path to the directory of a submodule, update it.
     ///

src/bootstrap/util.rs

@@ -16,11 +16,6 @@
 use crate::builder::Builder;
 use crate::config::{Config, TargetSelection};
 
-/// Returns the `name` as the filename of a static library for `target`.
-pub fn staticlib(name: &str, target: TargetSelection) -> String {
-    if target.contains("windows") { format!("{}.lib", name) } else { format!("lib{}.a", name) }
-}
-
 /// Given an executable called `name`, return the filename for the
 /// executable for a particular target.
 pub fn exe(name: &str, target: TargetSelection) -> String {
@@ -54,29 +49,7 @@ pub fn add_dylib_path(path: Vec<PathBuf>, cmd: &mut Command) {
     cmd.env(dylib_path_var(), t!(env::join_paths(list)));
 }
 
-/// Returns the environment variable which the dynamic library lookup path
-/// resides in for this platform.
-pub fn dylib_path_var() -> &'static str {
-    if cfg!(target_os = "windows") {
-        "PATH"
-    } else if cfg!(target_os = "macos") {
-        "DYLD_LIBRARY_PATH"
-    } else if cfg!(target_os = "haiku") {
-        "LIBRARY_PATH"
-    } else {
-        "LD_LIBRARY_PATH"
-    }
-}
-
-/// Parses the `dylib_path_var()` environment variable, returning a list of
-/// paths that are members of this lookup path.
-pub fn dylib_path() -> Vec<PathBuf> {
-    let var = match env::var_os(dylib_path_var()) {
-        Some(v) => v,
-        None => return vec![],
-    };
-    env::split_paths(&var).collect()
-}
+include!("dylib_util.rs");
 
 /// Adds a list of lookup paths to `cmd`'s link library lookup path.
 pub fn add_link_lib_path(path: Vec<PathBuf>, cmd: &mut Command) {
@@ -103,21 +76,6 @@ fn link_lib_path() -> Vec<PathBuf> {
     env::split_paths(&var).collect()
 }
 
-/// `push` all components to `buf`. On windows, append `.exe` to the last component.
-pub fn push_exe_path(mut buf: PathBuf, components: &[&str]) -> PathBuf {
-    let (&file, components) = components.split_last().expect("at least one component required");
-    let mut file = file.to_owned();
-
-    if cfg!(windows) {
-        file.push_str(".exe");
-    }
-
-    buf.extend(components);
-    buf.push(file);
-
-    buf
-}
-
 pub struct TimeIt(bool, Instant);
 
 /// Returns an RAII structure that prints out how long it took to drop.