[libclang] Add entry points that take a full command line including argv[0].

[bkramer]

Summary

This provides both a more uniform interface and makes libclang behave like
clang tooling wrt relative paths against argv[0]. This is necessary for
finding paths to a c++ standard library relative to a clang binary given
in a compilation database. It can also be used to find paths relative to
libclang.so if the full path to it is passed in.

[klimek]

include/clang-c/Index.h

5694–5695

We should probably expand on why users would want to use on or the other here...

[bkramer]

• Add a test case to make sure argv[0] handling actually works.
• Clarify comments a bit.

[klimek]

LG

include/clang-c/Index.h

clang_parseTranslationUnit2(CXIndex CIdx,
                             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 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
  * ORed together to specify which options should be used when
  * saving the translation unit.
  */
 enum CXSaveTranslationUnit_Flags {
   /**
CINDEX_LINKAGE int clang_indexSourceFile(CXIndexAction,
                                          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 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.
  * 
  * The order of callback invocations is not guaranteed to be the same as
  * when indexing a source file. The high level order will be:
  * 
  *   -Preprocessor callbacks invocations
  *   -Declaration/reference callbacks invocations

lib/Frontend/CreateInvocationFromCommandLine.cpp

 clang::createInvocationFromCommandLine(ArrayRef<const char *> ArgList,
                             IntrusiveRefCntPtr<DiagnosticsEngine> Diags) {
   if (!Diags.get()) {
     // No diagnostics engine was provided, so create our own diagnostics object
     // with the default options.
     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.
   TheDriver.setCheckInputsExist(false);
 
   std::unique_ptr<driver::Compilation> C(TheDriver.BuildCompilation(Args));
 
   // Just print the cc1 options if -### was present.

tools/diagtool/ShowEnabledWarnings.cpp

createDiagnostics(unsigned int argc, char **argv) {
 
   // Buffer diagnostics from argument parsing so that we can output them using a
   // well formed diagnostic object.
   TextDiagnosticBuffer *DiagsBuffer = new TextDiagnosticBuffer;
   IntrusiveRefCntPtr<DiagnosticsEngine> InterimDiags(
     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;
 
   // Build the diagnostics parser
   IntrusiveRefCntPtr<DiagnosticsEngine> FinalDiags =
     CompilerInstance::createDiagnostics(&Invocation->getDiagnosticOpts());
   if (!FinalDiags)
     return nullptr;

tools/libclang/CIndex.cpp

clang_parseTranslationUnit_Impl(CXIndex CIdx, const char *source_filename,
   bool FoundSpellCheckingArgument = false;
   for (int I = 0; I != num_command_line_args; ++I) {
     if (strcmp(command_line_args[I], "-fno-spell-checking") == 0 ||
         strcmp(command_line_args[I], "-fspell-checking") == 0) {
       FoundSpellCheckingArgument = true;
       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.
   // Put the source file after command_line_args otherwise if '-x' flag is
   // present it will be unused.
   if (source_filename)
     Args->push_back(source_filename);
 
enum CXErrorCode Result = clang_parseTranslationUnit2(
       unsaved_files, num_unsaved_files, options, &TU);
   (void)Result;
   assert((TU && Result == CXError_Success) ||
          (!TU && Result != CXError_Success));
   return TU;
 }
 
 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)
       *Log << command_line_args[i] << " ";
   }
 
   if (num_unsaved_files && !unsaved_files)
     return CXError_InvalidArguments;

tools/libclang/Indexing.cpp

int clang_indexSourceFile(CXIndexAction idxAction,
                           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) {
+  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)
       *Log << command_line_args[i] << " ";
   }
 
   if (num_unsaved_files && !unsaved_files)
     return CXError_InvalidArguments;