[clang] pass -fno-cxx-modules to clang -### instead of the clang -cc1 commands

Summary: -fno-cxx-modules is only supported by the clang driver.

Reviewed By: akotulski

Differential Revision: D4124273

fbshipit-source-id: cc3de93

infer/src/clang/ClangCommand.re

@@ -100,7 +100,6 @@ let clang_cc1_cmd_sanitizer cmd => {
     };
   let post_args_rev =
     [] |> IList.rev_append ["-include", Config.lib_dir /\/ "clang_wrappers" /\/ "global_defines.h"] |>
-    argv_do_if (has_flag cmd "-fmodules") (argv_cons "-fno-cxx-modules") |>
     /* Never error on warnings. Clang is often more strict than Apple's version.  These arguments
        are appended at the end to override previous opposite settings.  How it's done: suppress
        all the warnings, since there are no warnings, compiler can't elevate them to error

infer/src/clang/ClangWrapper.re

@@ -22,7 +22,18 @@ type action_item =
 let normalize (args: array string) :list action_item => {
   let cmd = ClangCommand.mk ClangQuotes.SingleQuotes args;
   let clang_hashhashhash =
-    Printf.sprintf "%s 2>&1" (ClangCommand.prepend_arg "-###" cmd |> ClangCommand.command_to_run);
+    Printf.sprintf
+      "%s 2>&1"
+      (
+        ClangCommand.prepend_arg "-###" cmd |>
+        /* c++ modules are not supported, so let clang know in case it was passed
+           "-fmodules". Unfortunately we cannot know accurately if "-fmodules" was passed because we
+           don't go into argument files at this point ("clang -### ..." will do that for us), so we
+           also pass "-Qunused-arguments" to silence the potential warning that "-fno-cxx-modules"
+           was ignored. Moreover, "-fno-cxx-modules" is only accepted by the clang driver so we have
+           to pass it now. */
+        ClangCommand.append_args ["-fno-cxx-modules", "-Qunused-arguments"] |> ClangCommand.command_to_run
+      );
   Logging.out "clang -### invocation: %s@\n" clang_hashhashhash;
   let normalized_commands = ref [];
   let one_line line =>