2 files changed, 53 insertions, 24 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 2a514ab1bd2..e6381fbe49f 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -10393,8 +10393,17 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
       Diag(var->getLocation(), diag::warn_missing_variable_declarations) << var;
   }
 
+  // Cache the result of checking for constant initialization.
+  Optional<bool> CacheHasConstInit;
+  const Expr *CacheCulprit;
+  auto checkConstInit = [&]() mutable {
+    if (!CacheHasConstInit)
+      CacheHasConstInit = var->getInit()->isConstantInitializer(
+            Context, var->getType()->isReferenceType(), &CacheCulprit);
+    return *CacheHasConstInit;
+  };
+
   if (var->getTLSKind() == VarDecl::TLS_Static) {
-    const Expr *Culprit;
     if (var->getType().isDestructedType()) {
       // GNU C++98 edits for __thread, [basic.start.term]p3:
       //   The type of an object with thread storage duration shall not
@@ -10402,17 +10411,17 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
       Diag(var->getLocation(), diag::err_thread_nontrivial_dtor);
       if (getLangOpts().CPlusPlus11)
         Diag(var->getLocation(), diag::note_use_thread_local);
-    } else if (getLangOpts().CPlusPlus && var->hasInit() &&
-               !var->getInit()->isConstantInitializer(
-                   Context, var->getType()->isReferenceType(), &Culprit)) {
-      // GNU C++98 edits for __thread, [basic.start.init]p4:
-      //   An object of thread storage duration shall not require dynamic
-      //   initialization.
-      // FIXME: Need strict checking here.
-      Diag(Culprit->getExprLoc(), diag::err_thread_dynamic_init)
-        << Culprit->getSourceRange();
-      if (getLangOpts().CPlusPlus11)
-        Diag(var->getLocation(), diag::note_use_thread_local);
+    } else if (getLangOpts().CPlusPlus && var->hasInit()) {
+      if (!checkConstInit()) {
+        // GNU C++98 edits for __thread, [basic.start.init]p4:
+        //   An object of thread storage duration shall not require dynamic
+        //   initialization.
+        // FIXME: Need strict checking here.
+        Diag(CacheCulprit->getExprLoc(), diag::err_thread_dynamic_init)
+          << CacheCulprit->getSourceRange();
+        if (getLangOpts().CPlusPlus11)
+          Diag(var->getLocation(), diag::note_use_thread_local);
+      }
     }
   }
 
@@ -10486,18 +10495,6 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
 
   if (!var->getDeclContext()->isDependentContext() &&
       Init && !Init->isValueDependent()) {
-    if (IsGlobal && !var->isConstexpr() &&
-        !getDiagnostics().isIgnored(diag::warn_global_constructor,
-                                    var->getLocation())) {
-      // Warn about globals which don't have a constant initializer.  Don't
-      // warn about globals with a non-trivial destructor because we already
-      // warned about them.
-      CXXRecordDecl *RD = baseType->getAsCXXRecordDecl();
-      if (!(RD && !RD->hasTrivialDestructor()) &&
-          !Init->isConstantInitializer(Context, baseType->isReferenceType()))
-        Diag(var->getLocation(), diag::warn_global_constructor)
-          << Init->getSourceRange();
-    }
 
     if (var->isConstexpr()) {
       SmallVector<PartialDiagnosticAt, 8> Notes;
@@ -10521,6 +10518,35 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
       // initialized by a constant expression if we check later.
       var->checkInitIsICE();
     }
+
+    // Don't emit further diagnostics about constexpr globals since they
+    // were just diagnosed.
+    if (!var->isConstexpr() && GlobalStorage &&
+            var->hasAttr<RequireConstantInitAttr>()) {
+      // FIXME: Need strict checking in C++03 here.
+      bool DiagErr = getLangOpts().CPlusPlus11
+          ? !var->checkInitIsICE() : !checkConstInit();
+      if (DiagErr) {
+        auto attr = var->getAttr<RequireConstantInitAttr>();
+        Diag(var->getLocation(), diag::err_require_constant_init_failed)
+          << Init->getSourceRange();
+        Diag(attr->getLocation(), diag::note_declared_required_constant_init_here)
+          << attr->getRange();
+      }
+    }
+    else if (!var->isConstexpr() && IsGlobal &&
+             !getDiagnostics().isIgnored(diag::warn_global_constructor,
+                                    var->getLocation())) {
+      // Warn about globals which don't have a constant initializer.  Don't
+      // warn about globals with a non-trivial destructor because we already
+      // warned about them.
+      CXXRecordDecl *RD = baseType->getAsCXXRecordDecl();
+      if (!(RD && !RD->hasTrivialDestructor())) {
+        if (!checkConstInit())
+          Diag(var->getLocation(), diag::warn_global_constructor)
+            << Init->getSourceRange();
+      }
+    }
   }
 
   // Require the destructor.
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 0471f65cccd..824d68e838e 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -5630,6 +5630,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case AttributeList::AT_VecTypeHint:
     handleVecTypeHint(S, D, Attr);
     break;
+  case AttributeList::AT_RequireConstantInit:
+    handleSimpleAttribute<RequireConstantInitAttr>(S, D, Attr);
+    break;
   case AttributeList::AT_InitPriority:
     handleInitPriorityAttr(S, D, Attr);
     break;