clang-tidy: Add driver mode argument

`clang-tidy` does not infer driver mode if it is not provided with a
JSON compilation database.  This is exactly the way cmake launches it.
Hence clang-tidy will only use the default driver mode.  Add an explicit
driver mode argument to avoid this.

2 files changed, 14 insertions, 2 deletions

diff --git a/Source/cmMakefileTargetGenerator.cxx b/Source/cmMakefileTargetGenerator.cxx
index 714d01e..a2fa3b1 100644
--- a/Source/cmMakefileTargetGenerator.cxx
+++ b/Source/cmMakefileTargetGenerator.cxx
@@ -782,7 +782,13 @@ void cmMakefileTargetGenerator::WriteObjectRuleFiles(
         }
         if (tidy && *tidy) {
           run_iwyu += " --tidy=";
-          run_iwyu += this->LocalGenerator->EscapeForShell(tidy);
+          const char* driverMode = this->Makefile->GetDefinition(
+            "CMAKE_" + lang + "_CLANG_TIDY_DRIVER_MODE");
+          if (!(driverMode && *driverMode)) {
+            driverMode = lang == "C" ? "gcc" : "g++";
+          }
+          run_iwyu += this->LocalGenerator->EscapeForShell(
+            cmStrCat(tidy, ";--driver-mode=", driverMode));
         }
         if (cpplint && *cpplint) {
           run_iwyu += " --cpplint=";
diff --git a/Source/cmNinjaTargetGenerator.cxx b/Source/cmNinjaTargetGenerator.cxx
index 455d809..5a9f74c 100644
--- a/Source/cmNinjaTargetGenerator.cxx
+++ b/Source/cmNinjaTargetGenerator.cxx
@@ -759,7 +759,13 @@ void cmNinjaTargetGenerator::WriteCompileRule(const std::string& lang,
       }
       if (tidy && *tidy) {
         run_iwyu += " --tidy=";
-        run_iwyu += this->GetLocalGenerator()->EscapeForShell(tidy);
+        const char* driverMode = this->Makefile->GetDefinition(
+          "CMAKE_" + lang + "_CLANG_TIDY_DRIVER_MODE");
+        if (!(driverMode && *driverMode)) {
+          driverMode = lang == "C" ? "gcc" : "g++";
+        }
+        run_iwyu += this->GetLocalGenerator()->EscapeForShell(
+          cmStrCat(tidy, ";--driver-mode=", driverMode));
       }
       if (cpplint && *cpplint) {
         run_iwyu += " --cpplint=";