1 files changed, 18 insertions, 2 deletions
diff --git a/lib/Basic/Targets.cpp b/lib/Basic/Targets.cpp
index a9667bb2dd..02b1610b0e 100644
--- a/lib/Basic/Targets.cpp
+++ b/lib/Basic/Targets.cpp
@@ -1481,7 +1481,15 @@ public:
     Builder.defineMacro("_X86_");
     Builder.defineMacro("__MSVCRT__");
     Builder.defineMacro("__MINGW32__");
-    Builder.defineMacro("__declspec", "__declspec");
+
+    // mingw32-gcc provides __declspec(a) as alias of __attribute__((a)).
+    // In contrast, clang-cc1 provides __declspec(a) with -fms-extensions.
+    if (Opts.Microsoft)
+      // Provide "as-is" __declspec.
+      Builder.defineMacro("__declspec", "__declspec");
+    else
+      // Provide alias of __attribute__ like mingw32-gcc.
+      Builder.defineMacro("__declspec(a)", "__attribute__((a))");
   }
 };
 } // end anonymous namespace
@@ -1631,7 +1639,15 @@ public:
     Builder.defineMacro("__MSVCRT__");
     Builder.defineMacro("__MINGW32__");
     Builder.defineMacro("__MINGW64__");
-    Builder.defineMacro("__declspec", "__declspec");
+
+    // mingw32-gcc provides __declspec(a) as alias of __attribute__((a)).
+    // In contrast, clang-cc1 provides __declspec(a) with -fms-extensions.
+    if (Opts.Microsoft)
+      // Provide "as-is" __declspec.
+      Builder.defineMacro("__declspec", "__declspec");
+    else
+      // Provide alias of __attribute__ like mingw32-gcc.
+      Builder.defineMacro("__declspec(a)", "__attribute__((a))");
   }
 };
 } // end anonymous namespace