Check if the archive has already been added to avoid duplicates

This avoids adding archives multiple times, which results in duplicate objects in the resulting rlib, leading to symbol collision and link failures. This could happen when crate contains multiple link attributes that all reference the same archive.
rust-lang · Centril · May 27, 2019 · May 27, 2019 · May 27, 2019 · May 27, 2019
commit 069c52fa111e592f65605c54f5e9b77be0676595
diff --git a/src/librustc_codegen_llvm/back/archive.rs b/src/librustc_codegen_llvm/back/archive.rs
@@ -36,11 +36,20 @@ enum Addition {
         name_in_archive: String,
     },
     Archive {
+        path: PathBuf,
         archive: ArchiveRO,
         skip: Box<dyn FnMut(&str) -> bool>,
     },
 }
 
+impl Addition {
+    fn path(&self) -> &Path {
+        match self {
+            Addition::File { path, .. } | Addition::Archive { path, .. } => path,
+        }
+    }
+}
+
 fn is_relevant_child(c: &Child<'_>) -> bool {
     match c.name() {
         Some(name) => !name.contains("SYMDEF"),
@@ -188,12 +197,16 @@ impl<'a> LlvmArchiveBuilder<'a> {
                       -> io::Result<()>
         where F: FnMut(&str) -> bool + 'static
     {
-        let archive = match ArchiveRO::open(archive) {
+        let archive_ro = match ArchiveRO::open(archive) {
             Ok(ar) => ar,
             Err(e) => return Err(io::Error::new(io::ErrorKind::Other, e)),
         };
+        if self.additions.iter().any(|ar| ar.path() == archive) {
+            return Ok(())
+        }
         self.additions.push(Addition::Archive {
-            archive,
+            path: archive.to_path_buf(),
+            archive: archive_ro,
             skip: Box::new(skip),
         });
         Ok(())
@@ -243,7 +256,7 @@ impl<'a> LlvmArchiveBuilder<'a> {
                         strings.push(path);
                         strings.push(name);
                     }
-                    Addition::Archive { archive, skip } => {
+                    Addition::Archive { archive, skip, .. } => {
                         for child in archive.iter() {
                             let child = child.map_err(string_to_io_error)?;
                             if !is_relevant_child(&child) {