Implement support for module requirements, which indicate the language

features needed for a particular module to be available. This allows
mixed-language modules, where certain headers only work under some
language variants (e.g., in C++, std.tuple might only be available in
C++11 mode).

llvm-svn: 147387

1 files changed, 18 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 440474b587a..dd48b2dc564 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2523,6 +2523,11 @@ void ASTReader::makeModuleVisible(Module *Mod,
       continue;
     }
     
+    if (!Mod->isAvailable()) {
+      // Modules that aren't available cannot be made visible.
+      continue;
+    }
+
     // Update the module's name visibility.
     Mod->NameVisibility = NameVisibility;
     
@@ -3247,6 +3252,19 @@ ASTReader::ASTReadResult ASTReader::ReadSubmoduleBlock(ModuleFile &F) {
       CurrentModule->UnresolvedExports.clear();
       break;
     }
+    case SUBMODULE_REQUIRES: {
+      if (First) {
+        Error("missing submodule metadata record at beginning of block");
+        return Failure;
+      }
+
+      if (!CurrentModule)
+        break;
+
+      CurrentModule->addRequirement(StringRef(BlobStart, BlobLen), 
+                                    Context.getLangOptions());
+      break;
+    }
     }
   }