From: Douglas Gregor <dgregor@apple.com>
Date: Sat, 26 Mar 2011 22:25:30 +0000 (+0000)
Subject: Improve -Wheader-hygiene to warn about using directives inside linkage
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9172aa685f3a1cbf991a2c1cd40905e4d64bfdf6;p=clang

Improve -Wheader-hygiene to warn about using directives inside linkage
specifications within the global scope, from Elliot Glaysher.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128352 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index b193c60218..07d60caf43 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -3817,6 +3817,19 @@ NamespaceDecl *Sema::getOrCreateStdNamespace() {
   return getStdNamespace();
 }
 
+/// \brief Determine whether a using statement is in a context where it will be
+/// apply in all contexts.
+static bool IsUsingDirectiveInToplevelContext(DeclContext *CurContext) {
+  switch (CurContext->getDeclKind()) {
+    case Decl::TranslationUnit:
+      return true;
+    case Decl::LinkageSpec:
+      return IsUsingDirectiveInToplevelContext(CurContext->getParent());
+    default:
+      return false;
+  }
+}
+
 Decl *Sema::ActOnUsingDirective(Scope *S,
                                           SourceLocation UsingLoc,
                                           SourceLocation NamespcLoc,
@@ -3902,7 +3915,7 @@ Decl *Sema::ActOnUsingDirective(Scope *S,
                                       SS.getWithLocInContext(Context),
                                       IdentLoc, Named, CommonAncestor);
 
-    if (CurContext->getDeclKind() == Decl::TranslationUnit &&
+    if (IsUsingDirectiveInToplevelContext(CurContext) &&
         !SourceMgr.isFromMainFile(IdentLoc)) {
       Diag(IdentLoc, diag::warn_using_directive_in_header);
     }
diff --git a/test/SemaCXX/warn-using-namespace-in-header.cpp b/test/SemaCXX/warn-using-namespace-in-header.cpp
index 393e097df5..e040ca74cb 100644
--- a/test/SemaCXX/warn-using-namespace-in-header.cpp
+++ b/test/SemaCXX/warn-using-namespace-in-header.cpp
@@ -7,3 +7,21 @@ using namespace dont_warn;
 
 // Warning is actually in the header but only the cpp file gets scanned.
 // expected-warning {{using namespace directive in global context in header}}
+
+
+
+
+
+
+
+
+
+// Warn inside linkage specs too.
+// expected-warning {{using namespace directive in global context in header}}
+
+
+
+
+
+
+// expected-warning {{using namespace directive in global context in header}}
diff --git a/test/SemaCXX/warn-using-namespace-in-header.h b/test/SemaCXX/warn-using-namespace-in-header.h
index 677c4ac51a..57bb5d91be 100644
--- a/test/SemaCXX/warn-using-namespace-in-header.h
+++ b/test/SemaCXX/warn-using-namespace-in-header.h
@@ -13,3 +13,30 @@ using namespace warn_in_header_in_global_context;
 namespace dont_warn_here {
 using namespace warn_in_header_in_global_context;
 }
+
+// We should warn in toplevel extern contexts.
+namespace warn_inside_linkage {}
+extern "C++" {
+using namespace warn_inside_linkage;
+}
+
+// This is really silly, but we should warn on it:
+extern "C++" {
+extern "C" {
+extern "C++" {
+using namespace warn_inside_linkage;
+}
+}
+}
+
+// But we shouldn't warn in extern contexts inside namespaces.
+namespace dont_warn_here {
+extern "C++" {
+using namespace warn_in_header_in_global_context;
+}
+}
+
+// We also shouldn't warn in case of functions.
+inline void foo() {
+  using namespace warn_in_header_in_global_context;
+}