[clang][Modules] Add -fsystem-module flag

The -fsystem-module flag is used when explicitly building a module. It
forces the module to be treated as a system module. This is used when
converting an implicit build to an explicit build to match the
systemness the implicit build would have had for a given module.

Differential Revision: https://reviews.llvm.org/D75395

1 files changed, 11 insertions, 2 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 8638d43..48c65ad 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1905,6 +1905,11 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   Opts.ModulesEmbedAllFiles = Args.hasArg(OPT_fmodules_embed_all_files);
   Opts.IncludeTimestamps = !Args.hasArg(OPT_fno_pch_timestamp);
   Opts.UseTemporary = !Args.hasArg(OPT_fno_temp_file);
+  Opts.IsSystemModule = Args.hasArg(OPT_fsystem_module);
+
+  if (Opts.ProgramAction != frontend::GenerateModule && Opts.IsSystemModule)
+    Diags.Report(diag::err_drv_argument_only_allowed_with) << "-fsystem-module"
+                                                           << "-emit-module";
 
   Opts.CodeCompleteOpts.IncludeMacros
     = Args.hasArg(OPT_code_completion_macros);
@@ -2061,12 +2066,16 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
         DashX = IK;
     }
 
+    bool IsSystem = false;
+
     // The -emit-module action implicitly takes a module map.
     if (Opts.ProgramAction == frontend::GenerateModule &&
-        IK.getFormat() == InputKind::Source)
+        IK.getFormat() == InputKind::Source) {
       IK = IK.withFormat(InputKind::ModuleMap);
+      IsSystem = Opts.IsSystemModule;
+    }
 
-    Opts.Inputs.emplace_back(std::move(Inputs[i]), IK);
+    Opts.Inputs.emplace_back(std::move(Inputs[i]), IK, IsSystem);
   }
 
   return DashX;