Introduce an ArchiveBuilderBuilder

This avoids monomorphizing all linker code for each codegen backend and
will allow passing in extra information to the archive builder from the
codegen backend.

src/archive.rs

@@ -1,7 +1,7 @@
 use std::fs::File;
 use std::path::{Path, PathBuf};
 
-use rustc_codegen_ssa::back::archive::ArchiveBuilder;
+use rustc_codegen_ssa::back::archive::{ArchiveBuilder, ArchiveBuilderBuilder};
 use rustc_session::Session;
 
 use rustc_session::cstore::DllImport;
@@ -21,41 +21,56 @@ enum ArchiveEntry {
     File(PathBuf),
 }
 
-pub struct ArArchiveBuilder<'a> {
-    config: ArchiveConfig<'a>,
-    src_archives: Vec<(PathBuf, ar::Archive<File>)>,
-    // Don't use `HashMap` here, as the order is important. `rust.metadata.bin` must always be at
-    // the end of an archive for linkers to not get confused.
-    entries: Vec<(String, ArchiveEntry)>,
-}
+pub struct ArArchiveBuilderBuilder;
 
-impl<'a> ArchiveBuilder<'a> for ArArchiveBuilder<'a> {
-    fn new(sess: &'a Session) -> Self {
+impl ArchiveBuilderBuilder for ArArchiveBuilderBuilder {
+    fn new_archive_builder<'a>(&self, sess: &'a Session) -> Box<dyn ArchiveBuilder<'a> + 'a> {
         let config = ArchiveConfig {
             sess,
             use_native_ar: false,
             // FIXME test for linux and System V derivatives instead
             use_gnu_style_archive: sess.target.options.archive_format == "gnu",
         };
 
-        ArArchiveBuilder {
+        Box::new(ArArchiveBuilder {
             config,
             src_archives: vec![],
             entries: vec![],
-        }
+        })
     }
 
+    fn create_dll_import_lib(
+        &self,
+        _sess: &Session,
+        _lib_name: &str,
+        _dll_imports: &[DllImport],
+        _tmpdir: &Path,
+    ) -> PathBuf {
+        unimplemented!();
+    }
+}
+
+pub struct ArArchiveBuilder<'a> {
+    config: ArchiveConfig<'a>,
+    src_archives: Vec<(PathBuf, ar::Archive<File>)>,
+    // Don't use `HashMap` here, as the order is important. `rust.metadata.bin` must always be at
+    // the end of an archive for linkers to not get confused.
+    entries: Vec<(String, ArchiveEntry)>,
+}
+
+impl<'a> ArchiveBuilder<'a> for ArArchiveBuilder<'a> {
     fn add_file(&mut self, file: &Path) {
         self.entries.push((
             file.file_name().unwrap().to_str().unwrap().to_string(),
             ArchiveEntry::File(file.to_owned()),
         ));
     }
 
-    fn add_archive<F>(&mut self, archive_path: &Path, mut skip: F) -> std::io::Result<()>
-    where
-        F: FnMut(&str) -> bool + 'static,
-    {
+    fn add_archive(
+        &mut self,
+        archive_path: &Path,
+        mut skip: Box<dyn FnMut(&str) -> bool + 'static>,
+    ) -> std::io::Result<()> {
         let mut archive = ar::Archive::new(std::fs::File::open(&archive_path)?);
         let archive_index = self.src_archives.len();
 
@@ -75,7 +90,7 @@ impl<'a> ArchiveBuilder<'a> for ArArchiveBuilder<'a> {
         Ok(())
     }
 
-    fn build(mut self, output: &Path) -> bool {
+    fn build(mut self: Box<Self>, output: &Path) -> bool {
         use std::process::Command;
 
         fn add_file_using_ar(archive: &Path, file: &Path) {
@@ -171,13 +186,4 @@ impl<'a> ArchiveBuilder<'a> for ArArchiveBuilder<'a> {
 
         any_members
     }
-
-    fn create_dll_import_lib(
-        _sess: &Session,
-        _lib_name: &str,
-        _dll_imports: &[DllImport],
-        _tmpdir: &Path,
-    ) -> PathBuf {
-        unimplemented!();
-    }
 }

src/lib.rs

@@ -133,8 +133,9 @@ impl CodegenBackend for GccCodegenBackend {
     fn link(&self, sess: &Session, codegen_results: CodegenResults, outputs: &OutputFilenames) -> Result<(), ErrorGuaranteed> {
         use rustc_codegen_ssa::back::link::link_binary;
 
-        link_binary::<crate::archive::ArArchiveBuilder<'_>>(
+        link_binary(
             sess,
+            &crate::archive::ArArchiveBuilderBuilder,
             &codegen_results,
             outputs,
         )