Index: include/clang-c/Index.h
===================================================================
--- include/clang-c/Index.h
+++ include/clang-c/Index.h
@@ -1289,6 +1289,16 @@
                             CXTranslationUnit *out_TU);
 
 /**
+ * \brief Same as clang_parseTranslationUnit2 but requires a full command line
+ * for \c command_line_args including argv[0].
+ */
+CINDEX_LINKAGE enum CXErrorCode clang_parseTranslationUnit2FullArgv(
+    CXIndex CIdx, const char *source_filename,
+    const char *const *command_line_args, int num_command_line_args,
+    struct CXUnsavedFile *unsaved_files, unsigned num_unsaved_files,
+    unsigned options, CXTranslationUnit *out_TU);
+
+/**
  * \brief Flags that control how translation units are saved.
  *
  * The enumerators in this enumeration type are meant to be bitwise
@@ -5681,6 +5691,17 @@
                                          unsigned TU_options);
 
 /**
+ * \brief Same as clang_indexSourceFile but requires a full command line
+ * for \c command_line_args including argv[0].
+ */
+CINDEX_LINKAGE int clang_indexSourceFileFullArgv(
+    CXIndexAction, CXClientData client_data, IndexerCallbacks *index_callbacks,
+    unsigned index_callbacks_size, unsigned index_options,
+    const char *source_filename, const char *const *command_line_args,
+    int num_command_line_args, struct CXUnsavedFile *unsaved_files,
+    unsigned num_unsaved_files, CXTranslationUnit *out_TU, unsigned TU_options);
+
+/**
  * \brief Index the given translation unit via callbacks implemented through
  * #IndexerCallbacks.
  * 
Index: lib/Frontend/CreateInvocationFromCommandLine.cpp
===================================================================
--- lib/Frontend/CreateInvocationFromCommandLine.cpp
+++ lib/Frontend/CreateInvocationFromCommandLine.cpp
@@ -39,15 +39,13 @@
     Diags = CompilerInstance::createDiagnostics(new DiagnosticOptions);
   }
 
-  SmallVector<const char *, 16> Args;
-  Args.push_back("<clang>"); // FIXME: Remove dummy argument.
-  Args.insert(Args.end(), ArgList.begin(), ArgList.end());
+  SmallVector<const char *, 16> Args(ArgList.begin(), ArgList.end());
 
   // FIXME: Find a cleaner way to force the driver into restricted modes.
   Args.push_back("-fsyntax-only");
 
   // FIXME: We shouldn't have to pass in the path info.
-  driver::Driver TheDriver("clang", llvm::sys::getDefaultTargetTriple(),
+  driver::Driver TheDriver(Args[0], llvm::sys::getDefaultTargetTriple(),
                            *Diags);
 
   // Don't check that inputs exist, they may have been remapped.
Index: tools/diagtool/ShowEnabledWarnings.cpp
===================================================================
--- tools/diagtool/ShowEnabledWarnings.cpp
+++ tools/diagtool/ShowEnabledWarnings.cpp
@@ -64,9 +64,11 @@
     new DiagnosticsEngine(DiagIDs, new DiagnosticOptions(), DiagsBuffer));
 
   // Try to build a CompilerInvocation.
+  SmallVector<const char *, 4> Args;
+  Args.push_back("diagtool");
+  Args.append(argv, argv + argc);
   std::unique_ptr<CompilerInvocation> Invocation(
-      createInvocationFromCommandLine(llvm::makeArrayRef(argv, argc),
-                                      InterimDiags));
+      createInvocationFromCommandLine(Args, InterimDiags));
   if (!Invocation)
     return nullptr;
 
Index: tools/libclang/CIndex.cpp
===================================================================
--- tools/libclang/CIndex.cpp
+++ tools/libclang/CIndex.cpp
@@ -3089,12 +3089,12 @@
       break;
     }
   }
-  if (!FoundSpellCheckingArgument)
-    Args->push_back("-fno-spell-checking");
-  
   Args->insert(Args->end(), command_line_args,
                command_line_args + num_command_line_args);
 
+  if (!FoundSpellCheckingArgument)
+    Args->insert(Args->begin() + 1, "-fno-spell-checking");
+
   // The 'source_filename' argument is optional.  If the caller does not
   // specify it then it is assumed that the source file is specified
   // in the actual argument list.
@@ -3157,14 +3157,23 @@
 }
 
 enum CXErrorCode clang_parseTranslationUnit2(
-    CXIndex CIdx,
-    const char *source_filename,
-    const char *const *command_line_args,
-    int num_command_line_args,
-    struct CXUnsavedFile *unsaved_files,
-    unsigned num_unsaved_files,
-    unsigned options,
-    CXTranslationUnit *out_TU) {
+    CXIndex CIdx, const char *source_filename,
+    const char *const *command_line_args, int num_command_line_args,
+    struct CXUnsavedFile *unsaved_files, unsigned num_unsaved_files,
+    unsigned options, CXTranslationUnit *out_TU) {
+  SmallVector<const char *, 4> Args;
+  Args.push_back("clang");
+  Args.append(command_line_args, command_line_args + num_command_line_args);
+  return clang_parseTranslationUnit2FullArgv(
+      CIdx, source_filename, Args.data(), Args.size(), unsaved_files,
+      num_unsaved_files, options, out_TU);
+}
+
+enum CXErrorCode clang_parseTranslationUnit2FullArgv(
+    CXIndex CIdx, const char *source_filename,
+    const char *const *command_line_args, int num_command_line_args,
+    struct CXUnsavedFile *unsaved_files, unsigned num_unsaved_files,
+    unsigned options, CXTranslationUnit *out_TU) {
   LOG_FUNC_SECTION {
     *Log << source_filename << ": ";
     for (int i = 0; i != num_command_line_args; ++i)
Index: tools/libclang/Indexing.cpp
===================================================================
--- tools/libclang/Indexing.cpp
+++ tools/libclang/Indexing.cpp
@@ -907,6 +907,22 @@
                           unsigned num_unsaved_files,
                           CXTranslationUnit *out_TU,
                           unsigned TU_options) {
+  SmallVector<const char *, 4> Args;
+  Args.push_back("clang");
+  Args.append(command_line_args, command_line_args + num_command_line_args);
+  return clang_indexSourceFileFullArgv(
+      idxAction, client_data, index_callbacks, index_callbacks_size,
+      index_options, source_filename, Args.data(), Args.size(), unsaved_files,
+      num_unsaved_files, out_TU, TU_options);
+}
+
+int clang_indexSourceFileFullArgv(
+    CXIndexAction idxAction, CXClientData client_data,
+    IndexerCallbacks *index_callbacks, unsigned index_callbacks_size,
+    unsigned index_options, const char *source_filename,
+    const char *const *command_line_args, int num_command_line_args,
+    struct CXUnsavedFile *unsaved_files, unsigned num_unsaved_files,
+    CXTranslationUnit *out_TU, unsigned TU_options) {
   LOG_FUNC_SECTION {
     *Log << source_filename << ": ";
     for (int i = 0; i != num_command_line_args; ++i)