[Modules] Make header inclusion order from umbrella dirs deterministic

Sort the headers by name before adding the includes in
collectModuleHeaderIncludes. This makes the include order for building
umbrellas deterministic across different filesystems and also guarantees
that the ASTWriter always dump top headers in the same order.

There's currently no good way to test for this behavior.

rdar://problem/28116411

llvm-svn: 289478

1 files changed, 11 insertions, 3 deletions

diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
index eb91940..ef008d1 100644
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -233,6 +233,7 @@ collectModuleHeaderIncludes(const LangOptions &LangOpts, FileManager &FileMgr,
     llvm::sys::path::native(UmbrellaDir.Entry->getName(), DirNative);
 
     vfs::FileSystem &FS = *FileMgr.getVirtualFileSystem();
+    SmallVector<std::pair<std::string, const FileEntry *>, 8> Headers;
     for (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 
@@ -263,13 +264,20 @@ collectModuleHeaderIncludes(const LangOptions &LangOpts, FileManager &FileMgr,
            ++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);
+      Headers.push_back(std::make_pair(RelativeHeader.str(), Header));
     }
 
     if (EC)
       return EC;
+
+    // Sort header paths and make the header inclusion order deterministic
+    // across different OSs and filesystems.
+    llvm::array_pod_sort(Headers.begin(), Headers.end());
+    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.