[cfe-commits] r147723 - in /cfe/trunk: include/clang/AST/DeclCXX.h include/clang/Basic/DiagnosticSemaKinds.td include/clang/Sema/ScopeInfo.h include/clang/Sema/Sema.h lib/AST/DeclCXX.cpp lib/Sema/Sema.cpp lib/Sema/SemaCodeComplete.cpp lib/Sema/Se

[John McCall]

On Jan 9, 2012, at 11:34 AM, Eli Friedman wrote:
> On Mon, Jan 9, 2012 at 11:09 AM, John McCall <rjmccall at apple.com> wrote:
>> On Jan 9, 2012, at 10:44 AM, Eli Friedman wrote:
>>> On Mon, Jan 9, 2012 at 9:26 AM, John McCall <rjmccall at apple.com> wrote:
>>>> On Jan 6, 2012, at 8:59 PM, Eli Friedman wrote:
>>>>> Modified: cfe/trunk/include/clang/Sema/ScopeInfo.h
>>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/ScopeInfo.h?rev=147723&r1=147722&r2=147723&view=diff
>>>>> ==============================================================================
>>>>> --- cfe/trunk/include/clang/Sema/ScopeInfo.h (original)
>>>>> +++ cfe/trunk/include/clang/Sema/ScopeInfo.h Fri Jan  6 22:59:52 2012
>>>>> @@ -189,15 +189,20 @@
>>>>>   /// \brief A mapping from the set of captured variables to the
>>>>>   /// fields (within the lambda class) that represent the captured variables.
>>>>>   llvm::DenseMap<VarDecl *, FieldDecl *> CapturedVariables;
>>>>> -
>>>>> +
>>>>>   /// \brief The list of captured variables, starting with the explicit
>>>>>   /// captures and then finishing with any implicit captures.
>>>>>   llvm::SmallVector<Capture, 4> Captures;
>>>>> -
>>>>> +
>>>>> +  // \brief Whether we have already captured 'this'.
>>>>> +  bool CapturesCXXThis;
>>>>> +
>>>>>   /// \brief The number of captures in the \c Captures list that are
>>>>>   /// explicit captures.
>>>>>   unsigned NumExplicitCaptures;
>>>>> -
>>>>> +
>>>>> +  LambdaCaptureDefault Default;
>>>>> +
>>>>>   /// \brief The field associated with the captured 'this' pointer.
>>>>>   FieldDecl *ThisCapture;
>>>>> 
>>>>> @@ -208,8 +213,9 @@
>>>>>   QualType ReturnType;
>>>>> 
>>>>>   LambdaScopeInfo(DiagnosticsEngine &Diag, CXXRecordDecl *Lambda)
>>>>> -    : FunctionScopeInfo(Diag), Lambda(Lambda),
>>>>> -      NumExplicitCaptures(0), ThisCapture(0) , HasImplicitReturnType(false)
>>>>> +    : FunctionScopeInfo(Diag), Lambda(Lambda), CapturesCXXThis(false),
>>>>> +      NumExplicitCaptures(0), Default(LCD_None), ThisCapture(0),
>>>>> +      HasImplicitReturnType(false)
>>>>>   {
>>>>>     Kind = SK_Lambda;
>>>>>   }
>>>> 
>>>> Please do abstract out the common capture functionality between this and
>>>> BlockScopeInfo.  There's at least one more kind of capture (VLA typedef)
>>>> that really ought to go here in both cases.
>>> 
>>> I don't think this will be much of a benefit, given that I can't think
>>> of any code that can handle both blocks and lambdas without caring
>>> which one is in use.  I can try it out anyway, I guess.
>>> 
>>> I do not follow how VLA typedefs are in any way related; they don't
>>> provide a function-like context (with labels etc.), and they don't
>>> capture local variables.
>> 
>> VLA typedefs capture values.  If you use a VLA typedef within a
>> block/lambda, those captured values need to be captured by the block/lambda.
> 
> In that sense, any statement which can contain an expression captures
> values.  That isn't relevant here.

We discussed this offline, but for the record, we're talking about code like this:

  void foo(int n) {
    typedef int array_type[n];
    n++;
    std::something([] { array_type arr; ... });
  }

This code should capture the bounds evaluated as part of the typedef.  Note
that this potentially propagates further, e.g.
  typedef int inner_array[n];
  typedef inner_array *outer_array[n];

Here a reference to outer_array must also cause a capture the bounds
used for inner_array.

We don't really need to support this right away, but we should probably
stop it from crashing / silently miscompiling. :)

John.