Add [extern_c] attribute for modules, allowing a C module to be imported within an extern "C" block in C++ code.

llvm-svn: 202615

1 files changed, 35 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 69dd4905cb5..abcd886da6b 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -12957,6 +12957,36 @@ Decl *Sema::ActOnFileScopeAsmDecl(Expr *expr,
   return New;
 }
 
+static void checkModuleImportContext(Sema &S, Module *M,
+                                     SourceLocation ImportLoc,
+                                     DeclContext *DC) {
+  if (auto *LSD = dyn_cast<LinkageSpecDecl>(DC)) {
+    switch (LSD->getLanguage()) {
+    case LinkageSpecDecl::lang_c:
+      if (!M->IsExternC) {
+        S.Diag(ImportLoc, diag::err_module_import_in_extern_c)
+          << M->getFullModuleName();
+        S.Diag(LSD->getLocStart(), diag::note_module_import_in_extern_c);
+        return;
+      }
+      break;
+    case LinkageSpecDecl::lang_cxx:
+      break;
+    }
+    DC = LSD->getParent();
+  }
+
+  while (isa<LinkageSpecDecl>(DC))
+    DC = DC->getParent();
+  if (!isa<TranslationUnitDecl>(DC)) {
+    S.Diag(ImportLoc, diag::err_module_import_not_at_top_level)
+      << M->getFullModuleName() << DC;
+    S.Diag(cast<Decl>(DC)->getLocStart(),
+           diag::note_module_import_not_at_top_level)
+      << DC;
+  }
+}
+
 DeclResult Sema::ActOnModuleImport(SourceLocation AtLoc, 
                                    SourceLocation ImportLoc, 
                                    ModuleIdPath Path) {
@@ -12965,7 +12995,9 @@ DeclResult Sema::ActOnModuleImport(SourceLocation AtLoc,
                                                 /*IsIncludeDirective=*/false);
   if (!Mod)
     return true;
-  
+
+  checkModuleImportContext(*this, Mod, ImportLoc, CurContext);
+
   SmallVector<SourceLocation, 2> IdentifierLocs;
   Module *ModCheck = Mod;
   for (unsigned I = 0, N = Path.size(); I != N; ++I) {
@@ -12987,6 +13019,8 @@ DeclResult Sema::ActOnModuleImport(SourceLocation AtLoc,
 }
 
 void Sema::ActOnModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
+  checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext);
+
   // FIXME: Should we synthesize an ImportDecl here?
   PP.getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, DirectiveLoc,
                                          /*Complain=*/true);