1 files changed, 16 insertions, 3 deletions
diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 6168057..dc361b2 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -364,6 +364,7 @@ static std::error_code collectModuleHeaderIncludes(
     llvm::sys::path::native(UmbrellaDir.Entry->getName(), DirNative);
 
     llvm::vfs::FileSystem &FS = FileMgr.getVirtualFileSystem();
+    SmallVector<std::pair<std::string, const FileEntry *>, 8> Headers;
     for (llvm::vfs::recursive_directory_iterator Dir(FS, DirNative, EC), End;
          Dir != End && !EC; Dir.increment(EC)) {
       // Check whether this entry has an extension typically associated with
@@ -394,13 +395,25 @@ static std::error_code collectModuleHeaderIncludes(
            ++It)
         llvm::sys::path::append(RelativeHeader, *It);
 
-      // Include this header as part of the umbrella directory.
-      Module->addTopHeader(*Header);
-      addHeaderInclude(RelativeHeader, Includes, LangOpts, Module->IsExternC);
+      std::string RelName = RelativeHeader.c_str();
+      Headers.push_back(std::make_pair(RelName, *Header));
     }
 
     if (EC)
       return EC;
+
+    // Sort header paths and make the header inclusion order deterministic
+    // across different OSs and filesystems.
+    llvm::sort(Headers.begin(), Headers.end(), [](
+      const std::pair<std::string, const FileEntry *> &LHS,
+      const std::pair<std::string, const FileEntry *> &RHS) {
+        return LHS.first < RHS.first;
+    });
+    for (auto &H : Headers) {
+      // Include this header as part of the umbrella directory.
+      Module->addTopHeader(H.second);
+      addHeaderInclude(H.first, Includes, LangOpts, Module->IsExternC);
+    }
   }
 
   // Recurse into submodules.