Always use pre-main instead of linkme

This approach is more portable and reliable.
nvzqz · Nov 17, 2023 · b27892a · b27892a
1 parent d60ad58
commit b27892a
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Showing 11 changed files with 60 additions and 122 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -10,6 +10,8 @@ Versioning](http://semver.org/spec/v2.0.0.html).
 
 ### Added
 
+- Support for NetBSD, DragonFly BSD, and Haiku OS by using pre-`main`.
+
 - Set global thread counts using:
   - [`Divan::threads`](https://docs.rs/divan/X.Y.Z/divan/struct.Divan.html#method.threads)
   - `--threads A B C...` CLI arg
@@ -57,6 +59,10 @@ Versioning](http://semver.org/spec/v2.0.0.html).
 - [`black_box`] inside benchmark loop when deferring [`Drop`] of outputs. This
   is now done after the loop.
 
+- [`linkme`](https://docs.rs/linkme) dependency in favor of pre-`main` to
+  register benchmarks and benchmark groups. This is generally be more portable
+  and reliable.
+
 ### Changed
 
 - Now calling [`black_box`] at the end of the benchmark loop when deferring use

diff --git a/Cargo.toml b/Cargo.toml
@@ -19,11 +19,6 @@ clap = { version = "4", default-features = false, features = ["std", "env"] }
 condtype = "1.3"
 regex = { package = "regex-lite", version = "0.1", default-features = false, features = ["std", "string"] }
 
-[target.'cfg(not(any(windows, target_os = "linux", target_os = "android")))'.dependencies]
-# We use linkme to make benchmark/group entries discoverable. On platforms where
-# it doesn't work, we instead use pre-main to build a linked list.
-linkme = { version = "0.3", default-features = false }
-
 [features]
 default = ["wrap_help"]
 help = ["clap/help"]

diff --git a/macros/src/attr_options.rs b/macros/src/attr_options.rs
@@ -24,9 +24,6 @@ pub(crate) struct AttrOptions {
     /// reference crate `x` instead.
     pub std_crate: proc_macro2::TokenStream,
 
-    /// `divan::__private::linkme`.
-    pub linkme_crate: proc_macro2::TokenStream,
-
     /// Custom name for the benchmark or group.
     pub name_expr: Option<Expr>,
 
@@ -162,7 +159,6 @@ impl AttrOptions {
 
         Ok(Self {
             std_crate: quote! { #private_mod::std },
-            linkme_crate: quote! { #private_mod::linkme },
             private_mod,
             name_expr,
             generic,

diff --git a/macros/src/lib.rs b/macros/src/lib.rs
@@ -26,6 +26,40 @@ impl Macro<'_> {
     }
 }
 
+/// Attributes applied to a `static` containing a pointer to a function to run
+/// before `main`.
+fn pre_main_attrs() -> proc_macro2::TokenStream {
+    quote! {
+        #[used]
+        #[cfg_attr(
+            // ELF
+            any(
+                target_os = "android",
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "haiku",
+                target_os = "illumos",
+                target_os = "linux",
+                target_os = "netbsd",
+                target_os = "openbsd",
+            ),
+            link_section = ".init_array",
+        )]
+        #[cfg_attr(
+            // Mach-O
+            any(
+                target_os = "ios",
+                target_os = "macos",
+                target_os = "tvos",
+                target_os = "watchos",
+            ),
+            link_section = "__DATA,__mod_init_func,mod_init_funcs",
+        )]
+        #[cfg_attr(windows, link_section = ".CRT$XCU")]
+    }
+}
+
 #[proc_macro_attribute]
 pub fn bench(options: TokenStream, item: TokenStream) -> TokenStream {
     let fn_item = item.clone();
@@ -38,7 +72,7 @@ pub fn bench(options: TokenStream, item: TokenStream) -> TokenStream {
     };
 
     // Items needed by generated code.
-    let AttrOptions { private_mod, linkme_crate, .. } = &options;
+    let AttrOptions { private_mod, .. } = &options;
 
     let fn_ident = &fn_sig.ident;
     let fn_name = fn_ident.to_string();
@@ -112,6 +146,8 @@ pub fn bench(options: TokenStream, item: TokenStream) -> TokenStream {
     let option_none = quote! { #private_mod::None };
     let option_some = quote! { #private_mod::Some };
 
+    let pre_main_attrs = pre_main_attrs();
+
     // Creates a `GroupEntry` static for generic benchmarks.
     let make_generic_group = |generic_benches: proc_macro2::TokenStream| {
         let entry = quote! {
@@ -122,33 +158,11 @@ pub fn bench(options: TokenStream, item: TokenStream) -> TokenStream {
         };
 
         quote! {
-            // Use a distributed slice via `linkme` by default.
-            #[cfg(not(any(
-                windows,
-                target_os = "linux",
-                target_os = "android",
-            )))]
-            #[#linkme_crate::distributed_slice(#private_mod::GROUP_ENTRIES)]
-            #[linkme(crate = #linkme_crate)]
-            #[doc(hidden)]
-            static #static_ident: #private_mod::GroupEntry = #entry;
-
-            // On other platforms we push this static into `GROUP_ENTRIES`
-            // before `main` is called.
-            #[cfg(any(
-                windows,
-                target_os = "linux",
-                target_os = "android",
-            ))]
+            // Push this static into `GROUP_ENTRIES` before `main` is called.
             static #static_ident: #private_mod::GroupEntry = {
                 {
                     // Add `push` to the initializer section.
-                    #[used]
-                    #[cfg_attr(
-                        any(target_os = "linux", target_os = "android"),
-                        link_section = ".init_array",
-                    )]
-                    #[cfg_attr(windows, link_section = ".CRT$XCU")]
+                    #pre_main_attrs
                     static PUSH: extern "C" fn() = push;
 
                     extern "C" fn push() {
@@ -225,33 +239,12 @@ pub fn bench(options: TokenStream, item: TokenStream) -> TokenStream {
                 };
 
                 quote! {
-                    // Use a distributed slice via `linkme` by default.
-                    #[cfg(not(any(
-                        windows,
-                        target_os = "linux",
-                        target_os = "android",
-                    )))]
-                    #[#linkme_crate::distributed_slice(#private_mod::BENCH_ENTRIES)]
-                    #[linkme(crate = #linkme_crate)]
-                    #[doc(hidden)]
-                    static #static_ident: #private_mod::BenchEntry = #entry;
-
-                    // On other platforms we push this static into
-                    // `BENCH_ENTRIES` before `main` is called.
-                    #[cfg(any(
-                        windows,
-                        target_os = "linux",
-                        target_os = "android",
-                    ))]
+                    // Push this static into `BENCH_ENTRIES` before `main` is
+                    // called.
                     static #static_ident: #private_mod::BenchEntry = {
                         {
                             // Add `push` to the initializer section.
-                            #[used]
-                            #[cfg_attr(
-                                any(target_os = "linux", target_os = "android"),
-                                link_section = ".init_array",
-                            )]
-                            #[cfg_attr(windows, link_section = ".CRT$XCU")]
+                            #pre_main_attrs
                             static PUSH: extern "C" fn() = push;
 
                             extern "C" fn push() {
@@ -365,7 +358,7 @@ pub fn bench_group(options: TokenStream, item: TokenStream) -> TokenStream {
     };
 
     // Items needed by generated code.
-    let AttrOptions { private_mod, linkme_crate, .. } = &options;
+    let AttrOptions { private_mod, .. } = &options;
 
     // TODO: Make module parsing cheaper by parsing only the necessary parts.
     let mod_item = item.clone();
@@ -393,41 +386,14 @@ pub fn bench_group(options: TokenStream, item: TokenStream) -> TokenStream {
 
     let meta = entry_meta_expr(&mod_name, &options, ignore_attr_ident);
 
-    let entry_static = quote! {
-        static #static_ident: #private_mod::GroupEntry = #private_mod::GroupEntry {
-            meta: #meta,
-            generic_benches: #private_mod::None,
-        };
-    };
+    let pre_main_attrs = pre_main_attrs();
 
     let generated_items = quote! {
-        // Use a distributed slice via `linkme` by default.
-        #[cfg(not(any(
-            windows,
-            target_os = "linux",
-            target_os = "android",
-        )))]
-        #[#linkme_crate::distributed_slice(#private_mod::GROUP_ENTRIES)]
-        #[linkme(crate = #linkme_crate)]
-        #[doc(hidden)]
-        #entry_static
-
-        // On other platforms we push this static into `GROUP_ENTRIES` before
-        // `main` is called.
-        #[cfg(any(
-            windows,
-            target_os = "linux",
-            target_os = "android",
-        ))]
+        // Push this static into `GROUP_ENTRIES` before `main` is called.
         static #static_ident: #private_mod::EntryList<#private_mod::GroupEntry> = {
             {
                 // Add `push` to the initializer section.
-                #[used]
-                #[cfg_attr(
-                    any(target_os = "linux", target_os = "android"),
-                    link_section = ".init_array",
-                )]
-                #[cfg_attr(windows, link_section = ".CRT$XCU")]
+                #pre_main_attrs
                 static PUSH: extern "C" fn() = push;
 
                 extern "C" fn push() {
@@ -436,7 +402,10 @@ pub fn bench_group(options: TokenStream, item: TokenStream) -> TokenStream {
             }
 
             #private_mod::EntryList::new({
-                #entry_static
+                static #static_ident: #private_mod::GroupEntry = #private_mod::GroupEntry {
+                    meta: #meta,
+                    generic_benches: #private_mod::None,
+                };
 
                 &#static_ident
             })

diff --git a/src/divan.rs b/src/divan.rs
@@ -97,7 +97,7 @@ impl Divan {
 
     pub(crate) fn run_action(&self, action: Action) {
         let mut tree: Vec<EntryTree> = if cfg!(miri) {
-            // Miri does not work with `linkme`.
+            // Miri does not work with our linker tricks.
             Vec::new()
         } else {
             let group_entries = &crate::entry::GROUP_ENTRIES;

diff --git a/src/entry/list.rs b/src/entry/list.rs
@@ -13,7 +13,6 @@ pub struct EntryList<T: 'static> {
 }
 
 impl<T> EntryList<T> {
-    #[cfg(any(windows, target_os = "linux", target_os = "android"))]
     pub(crate) const fn root() -> Self {
         Self { entry: None, next: AtomicPtr::new(ptr::null_mut()) }
     }
@@ -36,9 +35,6 @@ impl<T> EntryList<T> {
     }
 
     /// Creates an iterator over entries in `self`.
-    ///
-    /// We use `.iter()` to be a drop-in replacement for
-    /// `linkme::DistributedSlice`.
     #[inline]
     pub fn iter(&self) -> impl Iterator<Item = &T> {
         let mut list = Some(self);

diff --git a/src/entry/mod.rs b/src/entry/mod.rs
@@ -18,32 +18,11 @@ pub(crate) use tree::EntryTree;
 ///
 /// Note: generic-type benchmark entries are instead stored in `GROUP_ENTRIES`
 /// in `generic_benches`.
-#[cfg(any(windows, target_os = "linux", target_os = "android"))]
 pub static BENCH_ENTRIES: EntryList<BenchEntry> = EntryList::root();
 
-/// Benchmark entries generated by `#[divan::bench]`.
-///
-/// Note: generic-type benchmark entries are instead stored in `GROUP_ENTRIES`
-/// in `generic_benches`.
-#[cfg(not(any(windows, target_os = "linux", target_os = "android")))]
-#[cfg_attr(
-    not(any(windows, target_os = "linux", target_os = "android")),
-    linkme::distributed_slice
-)]
-pub static BENCH_ENTRIES: [BenchEntry] = [..];
-
 /// Group entries generated by `#[divan::bench_group]`.
-#[cfg(any(windows, target_os = "linux", target_os = "android"))]
 pub static GROUP_ENTRIES: EntryList<GroupEntry> = EntryList::root();
 
-/// Group entries generated by `#[divan::bench_group]`.
-#[cfg(not(any(windows, target_os = "linux", target_os = "android")))]
-#[cfg_attr(
-    not(any(windows, target_os = "linux", target_os = "android")),
-    linkme::distributed_slice
-)]
-pub static GROUP_ENTRIES: [GroupEntry] = [..];
-
 /// Compile-time entry for a benchmark, generated by `#[divan::bench]`.
 pub struct BenchEntry {
     /// Entry metadata.

diff --git a/src/private.rs b/src/private.rs
@@ -3,9 +3,6 @@ pub use std::{
     self, any, borrow::Cow, default::Default, iter::FromIterator, option::Option::*, sync::OnceLock,
 };
 
-#[cfg(not(any(windows, target_os = "linux", target_os = "android")))]
-pub use linkme;
-
 pub use crate::{
     bench::BenchOptions,
     entry::{

diff --git a/tests/attr_options.rs b/tests/attr_options.rs
@@ -1,6 +1,6 @@
 // Tests that attribute options produce the correct results.
 
-// Miri does not work with `linkme`.
+// Miri cannot discover benchmarks.
 #![cfg(not(miri))]
 
 use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};

diff --git a/tests/entry_properties.rs b/tests/entry_properties.rs
@@ -1,6 +1,6 @@
 // Tests that entry benchmarks/groups have correct generated properties.
 
-// Miri does not work with `linkme`.
+// Miri cannot discover benchmarks.
 #![cfg(not(miri))]
 
 use divan::__private::{EntryMeta, BENCH_ENTRIES, GROUP_ENTRIES};

diff --git a/tests/weird_usage.rs b/tests/weird_usage.rs
@@ -1,6 +1,6 @@
 // Tests that ensure weird (but valid) usage behave as expected.
 
-// Miri does not work with `linkme`.
+// Miri cannot discover benchmarks.
 #![cfg(not(miri))]
 
 use std::time::Duration;