[cfe-commits] r171912 - in /cfe/trunk: include/clang/Basic/DiagnosticSemaKinds.td lib/Sema/SemaExpr.cpp test/SemaObjCXX/capturing-flexible-array-in-block.mm

[Eli Friedman]

On Tue, Jan 8, 2013 at 3:47 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> On Tue, Jan 8, 2013 at 3:29 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
>> On Tue, Jan 8, 2013 at 3:17 PM, Fariborz Jahanian <fjahanian at apple.com> wrote:
>>> Author: fjahanian
>>> Date: Tue Jan  8 17:17:51 2013
>>> New Revision: 171912
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=171912&view=rev
>>> Log:
>>> 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
>>>
>>> Added:
>>>     cfe/trunk/test/SemaObjCXX/capturing-flexible-array-in-block.mm
>>> Modified:
>>>     cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>     cfe/trunk/lib/Sema/SemaExpr.cpp
>>>
>>> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=171912&r1=171911&r2=171912&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Jan  8 17:17:51 2013
>>> @@ -4224,6 +4224,9 @@
>>>  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 @@
>>>    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">;
>>>
>>> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=171912&r1=171911&r2=171912&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
>>> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Tue Jan  8 17:17:51 2013
>>> @@ -10759,7 +10759,22 @@
>>>        }
>>>        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) {
>>>
>>> Added: cfe/trunk/test/SemaObjCXX/capturing-flexible-array-in-block.mm
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaObjCXX/capturing-flexible-array-in-block.mm?rev=171912&view=auto
>>> ==============================================================================
>>> --- cfe/trunk/test/SemaObjCXX/capturing-flexible-array-in-block.mm (added)
>>> +++ cfe/trunk/test/SemaObjCXX/capturing-flexible-array-in-block.mm Tue Jan  8 17:17:51 2013
>>> @@ -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}}
>>> +}
>>
>> We can do whatever we want with blocks, but the C++11 standard doesn't
>> allow us to reject this construct for lambda expressions.
>
> C++11 doesn't have flexible array members. The diagnostic seems
> sensible to me for lambdas.

Oh, oops... clang is missing a diagnostic here.

-Eli