Check module signature when the module has already been loaded

We may need to verify the signature on subsequent imports as well, just
like we verify the size/modtime:
@import A;
@import B; // imports A
@import C; // imports A

llvm-svn: 221569

1 files changed, 13 insertions, 7 deletions

diff --git a/clang/lib/Serialization/ModuleManager.cpp b/clang/lib/Serialization/ModuleManager.cpp
index 3baaa0a4b28..b5ee4145020 100644
--- a/clang/lib/Serialization/ModuleManager.cpp
+++ b/clang/lib/Serialization/ModuleManager.cpp
@@ -132,21 +132,27 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
     // Initialize the stream
     New->StreamFile.init((const unsigned char *)New->Buffer->getBufferStart(),
                          (const unsigned char *)New->Buffer->getBufferEnd());
+  }
+
+  if (ExpectedSignature) {
+    if (NewModule)
+      ModuleEntry->Signature = ReadSignature(ModuleEntry->StreamFile);
+    else
+      assert(ModuleEntry->Signature == ReadSignature(ModuleEntry->StreamFile));
 
-    if (ExpectedSignature) {
-      New->Signature = ReadSignature(New->StreamFile);
-      if (New->Signature != ExpectedSignature) {
-        ErrorStr = New->Signature ? "signature mismatch"
-                                  : "could not read module signature";
+    if (ModuleEntry->Signature != ExpectedSignature) {
+      ErrorStr = ModuleEntry->Signature ? "signature mismatch"
+                                        : "could not read module signature";
 
+      if (NewModule) {
         // Remove the module file immediately, since removeModules might try to
         // invalidate the file cache for Entry, and that is not safe if this
         // module is *itself* up to date, but has an out-of-date importer.
         Modules.erase(Entry);
         Chain.pop_back();
-        delete New;
-        return OutOfDate;
+        delete ModuleEntry;
       }
+      return OutOfDate;
     }
   }