Fix use-after-free and spurious error during module load

FileManager::invalidateCache is not safe to call when there may be
existing references to the file. What module load failure needs is
to refresh so stale stat() info isn't stored.

This may be the last user of invalidateCache; I'll take a look and
remove it if possible in a future commit.

This caused a use-after-free error as well as a spurious error message
that a module was "found in both 'X.pcm' and 'X.pcm'" in some cases.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209138 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Serialization/ModuleManager.cpp

@@ -152,9 +152,20 @@ void ModuleManager::removeModules(ModuleIterator first, ModuleIterator last,
 
   // Delete the modules and erase them from the various structures.
   for (ModuleIterator victim = first; victim != last; ++victim) {
-    Modules.erase((*victim)->File);
+    const FileEntry *F = (*victim)->File;
+    Modules.erase(F);
+
+    // Refresh the stat() information for the module file so stale information
+    // doesn't get stored accidentally.
+    vfs::Status UpdatedStat;
+    if (FileMgr.getNoncachedStatValue(F->getName(), UpdatedStat)) {
+      llvm::report_fatal_error(Twine("module file '") + F->getName() +
+                               "' removed after it has been used");
+    } else {
+      FileMgr.modifyFileEntry(const_cast<FileEntry *>(F), UpdatedStat.getSize(),
+          UpdatedStat.getLastModificationTime().toEpochTime());
+    }
 
-    FileMgr.invalidateCache((*victim)->File);
     if (modMap) {
       StringRef ModuleName = (*victim)->ModuleName;
       if (Module *mod = modMap->findModule(ModuleName)) {

test/Modules/load-after-failure.m

@@ -0,0 +1,25 @@
+// REQUIRES: shell
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+
+// RUN: echo '@import B;' > %t/A.h
+// RUN: echo '@import C;' > %t/B.h
+// RUN: echo '@import D;' >> %t/B.h
+// RUN: echo '// C.h' > %t/C.h
+// RUN: echo '// D.h' > %t/D.h
+// RUN: echo 'module A { header "A.h" }' > %t/module.modulemap
+// RUN: echo 'module B { header "B.h" }' >> %t/module.modulemap
+// RUN: echo 'module C { header "C.h" }' >> %t/module.modulemap
+// RUN: echo 'module D { header "D.h" }' >> %t/module.modulemap
+
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %t %s -verify
+// RUN: echo " " >> %t/D.h
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %t %s -verify
+// expected-no-diagnostics
+
+
+@import C;
+@import A;
+@import C;
+// When compiling A, C will be be loaded then removed when D fails. Ensure
+// this does not cause problems importing C again later.