[lld] [lld-macho] Support archives without index (PR #132942)

[Leonard Grey via llvm-commits]

================
@@ -2156,9 +2156,34 @@ ArchiveFile::ArchiveFile(std::unique_ptr<object::Archive> &&f, bool forceHidden)
 void ArchiveFile::addLazySymbols() {
   // Avoid calling getMemoryBufferRef() on zero-symbol archive
   // since that crashes.
-  if (file->isEmpty() || file->getNumberOfSymbols() == 0)
+  if (file->isEmpty())
     return;
 
+  if (file->getNumberOfSymbols() == 0) {
+    // No index, treat each child as a lazy object file.
+    Error e = Error::success();
+    for (const object::Archive::Child &c : file->children(e)) {
+      // Check `seen` but don't insert so a future eager load can still happen.
+      if (seen.contains(c.getChildOffset()))
+        continue;
+      if (!seenLazy.insert(c.getChildOffset()).second) {
+        continue;
+      }
+      // First check seen.
+      // Then, write to and check seenLazy
----------------
speednoisemovement wrote:

Old diff that got cleaned up, this was my todo list :D

https://github.com/llvm/llvm-project/pull/132942