Check that index-test uses an up-to-date AST file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74214 91177308-0d34-0410-b5e6-96231b3b80d8

tools/index-test/index-test.cpp

@@ -88,6 +88,18 @@ int main(int argc, char **argv) {
   if (!PointAtLocation.empty()) {
     const std::string &Filename = PointAtLocation[0].FileName;
     const FileEntry *File = FileMgr.getFile(Filename);
+
+    // Safety check. Using an out-of-date AST file will only lead to crashes
+    // or incorrect results.
+    // FIXME: Check all the source files that make up the AST file.
+    const FileEntry *ASTFile = FileMgr.getFile(InFile);
+    if (File->getModificationTime() > ASTFile->getModificationTime()) {
+      llvm::errs() << "[" << InFile << "] Error: " <<
+        "Pointing at a source file which was modified after creating "
+        "the AST file\n";
+      return 1;
+    }
+
     if (File == 0) {
       llvm::errs() << "File '" << Filename << "' does not exist\n";
       return 1;