On Jan 9, 2012, at 11:34 AM, Eli Friedman wrote:
> On Mon, Jan 9, 2012 at 11:09 AM, John McCall <[email protected]> wrote:
>> On Jan 9, 2012, at 10:44 AM, Eli Friedman wrote:
>>> On Mon, Jan 9, 2012 at 9:26 AM, John McCall <[email protected]> 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.
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