Index: lld/COFF/InputFiles.cpp
===================================================================
--- lld/COFF/InputFiles.cpp
+++ lld/COFF/InputFiles.cpp
@@ -500,6 +500,17 @@
     leaderSelection = selection = IMAGE_COMDAT_SELECT_LARGEST;
   }
 
+  // GCCs __declspec(selectany) doesn't actually pick "any" but "same size as".
+  // Clang on the other hand picks "any". To be able to link two object files
+  // with a __declspec(selectany) declaration, one compiled with gcc and the other
+  // with clang, we merge them as proper "any"
+  if (config->mingw && ((selection == IMAGE_COMDAT_SELECT_ANY &&
+                         leaderSelection == IMAGE_COMDAT_SELECT_SAME_SIZE) ||
+                        (selection == IMAGE_COMDAT_SELECT_SAME_SIZE &&
+                         leaderSelection == IMAGE_COMDAT_SELECT_ANY))) {
+    leaderSelection = selection = IMAGE_COMDAT_SELECT_ANY;
+  }
+
   // Other than that, comdat selections must match.  This is a bit more
   // strict than link.exe which allows merging "any" and "largest" if "any"
   // is the first symbol the linker sees, and it allows merging "largest"