objectiveC blocks: It is impractical to capture

struct variables with flexiable array members in
blocks (and lambdas). Issue error instead of
crashing in IRGen. // rdar://12655829

llvm-svn: 171912

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -4224,6 +4224,9 @@ def err_unexpected_interface : Error<
 def err_ref_non_value : Error<"%0 does not refer to a value">;
 def err_ref_vm_type : Error<
   "cannot refer to declaration with a variably modified type inside block">;
+def err_ref_flexarray_type : Error<
+  "cannot refer to declaration of structure variable with flexible array member "
+  "inside block">;
 def err_ref_array_type : Error<
   "cannot refer to declaration with an array type inside block">;
 def err_property_not_found : Error<
@@ -4609,6 +4612,9 @@ let CategoryName = "Lambda Issue" in {
   def err_lambda_capture_vm_type : Error<
     "variable %0 with variably modified type cannot be captured in "
     "a lambda expression">;
+  def err_lambda_capture_flexarray_type : Error<
+    "variable %0 with flexible array member cannot be captured in "
+    "a lambda expression">;
   def err_lambda_impcap : Error<
     "variable %0 cannot be implicitly captured in a lambda with no "
     "capture-default specified">;

clang/lib/Sema/SemaExpr.cpp

@@ -10759,7 +10759,22 @@ bool Sema::tryCaptureVariable(VarDecl *Var, SourceLocation Loc,
       }
       return true;
     }
-
+    // Prohibit prohibit structs with flexisble array members too.
+    // We cannot capture what is in the tail end of the struct.
+    if (const RecordType *VTTy = Var->getType()->getAs<RecordType>()) {
+      if (VTTy->getDecl()->hasFlexibleArrayMember()) {
+        if (BuildAndDiagnose) {
+          if (IsBlock)
+            Diag(Loc, diag::err_ref_flexarray_type);
+          else
+            Diag(Loc, diag::err_lambda_capture_flexarray_type)
+              << Var->getDeclName();
+          Diag(Var->getLocation(), diag::note_previous_decl)
+            << Var->getDeclName();
+        }
+        return true;
+      }
+    }
     // Lambdas are not allowed to capture __block variables; they don't
     // support the expected semantics.
     if (IsLambda && HasBlocksAttr) {

clang/test/SemaObjCXX/capturing-flexible-array-in-block.mm

@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -fsyntax-only -fblocks -verify -std=c++11 %s
+// rdar://12655829
+
+void f() {
+  struct { int x; int y[]; } a; // expected-note 2 {{'a' declared here}}
+  ^{return a.x;}(); // expected-error {{cannot refer to declaration of structure variable with flexible array member inside block}}
+
+  [] {return a.x;}(); // expected-error {{variable 'a' with flexible array member cannot be captured in a lambda expression}}
+}