Add option "--driver-mode" to config driver mode used by clang-tidy.

clang-tidy can't specify driver mode from command line. It will cause
problems when it is used with visual studio compiler (cl.exe). For
example, option of cl.exe can be started with either '-' or '/'. But
with default driver mode, you can only use '-' with clang-tidy.

	cl.exe a.cpp /Iinclude

can be success, but

	clang-tidy.exe a.cpp /Iinclude

may fail because /Iinclude can't be recongized by default driver mode of
clang-tidy. You need change the above line to:

	clang-tidy.exe a.cpp -Iinclude

One workaround is passing "--driver-mode=cl" after "--":

	clang-tidy.exe a.cpp -- --driver-mode

But this is not ideal. Generally, the options follow "--" should be
compiler options. "--driver-mode" is not the option of cl.exe. cl.exe
will generate "unknown option" warning.

This change adding an option "--driver-mode" to clang-tidy itself tries
to solve this problem. User can specify "gcc", "g++", "cpp", and "cl"
four modes. This option is optional. If this option is not specified,
the default driver mode will be used.

Author: xieyubo

clang-tools-extra/docs/clang-tidy/index.rst

@@ -134,6 +134,12 @@ An overview of all the command-line options:
                                      When the value is empty, clang-tidy will
                                      attempt to find a file named .clang-tidy for
                                      each source file in its parent directories.
+    --driver-mode                  -
+                                     Specify the driver mode:
+                                       - gcc: gcc mode
+                                       - g++: g++ mode
+                                       - cpp: cpp mode
+                                       - cl:  cl  mode
     --dump-config                  -
                                      Dumps configuration in the YAML format to
                                      stdout. This option can be used along with a

clang/lib/Tooling/CommonOptionsParser.cpp

@@ -23,6 +23,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Driver/Options.h"
 #include "clang/Tooling/CommonOptionsParser.h"
 #include "clang/Tooling/Tooling.h"
 #include "llvm/Support/CommandLine.h"
@@ -92,6 +93,21 @@ llvm::Error CommonOptionsParser::init(
       cl::Positional, cl::desc("<source0> [... <sourceN>]"), OccurrencesFlag,
       cl::cat(Category), cl::sub(*cl::AllSubCommands));
 
+  static cl::list<std::string> DriverMode(
+	  "driver-mode", cl::desc(R"(
+Specify the driver mode:
+  - gcc: gcc mode
+  - g++: g++ mode
+  - cpp: cpp mode
+  - cl:  cl  mode
+)"),
+      cl::Optional, cl::cat(Category),
+      cl::sub(*cl::AllSubCommands));
+
+  assert(driver::getDriverOptTable()
+             .getOption(driver::options::OPT_driver_mode)
+             .getPrefixedName() == "--driver-mode=");
+
   static cl::list<std::string> ArgsAfter(
       "extra-arg",
       cl::desc("Additional argument to append to the compiler command line"),

clang/lib/Tooling/CompilationDatabase.cpp

@@ -65,8 +65,8 @@ CompilationDatabase::loadFromDirectory(StringRef BuildDirectory,
                                        std::string &ErrorMessage) {
   llvm::raw_string_ostream ErrorStream(ErrorMessage);
   for (CompilationDatabasePluginRegistry::iterator
-       It = CompilationDatabasePluginRegistry::begin(),
-       Ie = CompilationDatabasePluginRegistry::end();
+           It = CompilationDatabasePluginRegistry::begin(),
+           Ie = CompilationDatabasePluginRegistry::end();
        It != Ie; ++It) {
     std::string DatabaseErrorMessage;
     std::unique_ptr<CompilationDatabasePlugin> Plugin(It->instantiate());
@@ -113,7 +113,7 @@ CompilationDatabase::autoDetectFromSource(StringRef SourceFile,
 
   if (!DB)
     ErrorMessage = ("Could not auto-detect compilation database for file \"" +
-                   SourceFile + "\"\n" + ErrorMessage).str();
+                    SourceFile + "\"\n" + ErrorMessage).str();
   return DB;
 }
 
@@ -353,6 +353,19 @@ FixedCompilationDatabase::loadFromCommandLine(int &Argc,
   std::vector<const char *> CommandLine(DoubleDash + 1, Argv + Argc);
   Argc = DoubleDash - Argv;
 
+  // If find "--driver-mode" option, we need insert this option to CommandLine,
+  // so that Driver can be set to correct driver mode.
+  const std::string DriverModePrefix =
+      driver::getDriverOptTable()
+          .getOption(driver::options::OPT_driver_mode)
+          .getPrefixedName();
+  for (int i = 0; i < Argc; ++i) {
+    if (llvm::StringRef(Argv[i]).startswith(DriverModePrefix)) {
+      CommandLine.insert(CommandLine.begin(), Argv[i]);
+      break;
+    }
+  }
+
   std::vector<std::string> StrippedArgs;
   if (!stripPositionalArgs(CommandLine, StrippedArgs, ErrorMsg))
     return nullptr;
@@ -406,7 +419,7 @@ class FixedCompilationDatabasePlugin : public CompilationDatabasePlugin {
 } // namespace
 
 static CompilationDatabasePluginRegistry::Add<FixedCompilationDatabasePlugin>
-X("fixed-compilation-database", "Reads plain-text flags file");
+    X("fixed-compilation-database", "Reads plain-text flags file");
 
 namespace clang {
 namespace tooling {