Il giorno 24/ott/2011, alle ore 17:22, Douglas Gregor ha scritto:
> ExprResult ImpCastExprToType(Expr *E, QualType Type, CastKind CK,
> ExprValueKind VK = VK_RValue,
> - const CXXCastPath *BasePath = 0,
> - CheckedConversionKind CCK
> - = CCK_ImplicitConversion);
> + const CXXCastPath *BasePath = 0);
>
> I'm slightly nervous about the two defaulted arguments here, since '0' can be
> silently passed for either of them, but I guess it works since '0' is
> CCK_ImplicitConversion anyway :)
>
> @@ -2193,13 +2192,13 @@
> return Owned(From);
> }
>
> -/// PerformImplicitConversion - Perform an implicit conversion of the
> +/// PerformConversion - Perform a conversion of the
> /// expression From to the type ToType by following the standard
> /// conversion sequence SCS. Returns the converted
> /// expression. Flavor is the context in which we're performing this
> /// conversion, for use in error messages.
> ExprResult
> -Sema::PerformImplicitConversion(Expr *From, QualType ToType,
> +Sema::PerformConversion(Expr *From, QualType ToType,
> const StandardConversionSequence& SCS,
> AssignmentAction Action,
> CheckedConversionKind CCK) {
> @@ -2277,20 +2276,20 @@
> case ICK_Array_To_Pointer:
> FromType = Context.getArrayDecayedType(FromType);
> From = ImpCastExprToType(From, FromType, CK_ArrayToPointerDecay,
> - VK_RValue, /*BasePath=*/0, CCK).take();
> + VK_RValue, /*BasePath=*/0).take();
> break;
>
> case ICK_Function_To_Pointer:
> FromType = Context.getPointerType(FromType);
> From = ImpCastExprToType(From, FromType, CK_FunctionToPointerDecay,
> - VK_RValue, /*BasePath=*/0, CCK).take();
> + VK_RValue, /*BasePath=*/0).take();
> break;
>
> default:
> llvm_unreachable("Improper first standard conversion");
> }
>
> I think you'll want to count the # of necessary conversions a bit more
> closely here, or maybe compute the number ahead of time. This still creates
> an extra conversion on code like this:
>
> struct A { };
>
> void f(A as[]) {
> static_cast<const A*>(as);
> }
>
> by producing
>
> (CXXStaticCastExpr 0x7f823203dde8 <line:4:3, col:27> 'const struct A *'
> static_cast<const struct A *> <NoOp>
> (ImplicitCastExpr 0x7f823203ddd0 <col:25> 'const struct A *' <NoOp>
> (ImplicitCastExpr 0x7f823203ddb8 <col:25> 'struct A *' <LValueToRValue>
> (DeclRefExpr 0x7f823203dd50 <col:25> 'struct A *' lvalue ParmVar
> 0x7f823203dbf0 'as' 'struct A *')))))
>
> Index: lib/Sema/SemaCast.cpp
> ===================================================================
> --- lib/Sema/SemaCast.cpp (revision 142579)
> +++ lib/Sema/SemaCast.cpp (working copy)
> @@ -289,6 +289,18 @@
> return ExprError();
> }
>
> + // CheckStaticCast _may_ have already created the cast node. Let's check
> + if(CXXStaticCastExpr *Cast =
> dyn_cast<CXXStaticCastExpr>(Op.SrcExpr.get()))
> + {
> + if(!Cast->getTypeInfoAsWritten())
> + {
> + Cast->setTypeInfoAsWritten(DestTInfo);
> + Cast->setOperatorLoc(OpLoc);
> + Cast->setRParenLoc(Parens.getEnd());
> + return Op.complete(Cast);
> + }
> + }
> +
>
> This feels a little shaky. I assume that the inner "if" is intended to make
> sure we don't cannibalize the inner "if" for something like
>
> static_cast<int>(static_cast<float>(something))
>
> However, I'd feel far better if we had a more direct way to signal to this
> code that the CXXStaticCastExpr has already been created. Also, it seems like
> some assertions comparing Op.Kind to Cast->getCastKind() and comparing the
> resulting types would be helpful to flush out any remaining issues.
>
> Oh, and '{'s up on the line above, rather than on their own line, please.
>
> The changes to Initialization.h (e.g., SIK_DirectCast -> SIK_DirectStaticCast
> and related) could go in at any time, if you'd like to tease these out from
> the main part of the patch.
> Hello. I've attached a patch that corrects what you pointed out. The issue about FunctionToPointer and ArrayToPointer decays persists, because they're handled in a very different way and they'll require a future new patch. I've removed the "shaky if" by setting a boolean parameter in CheckStaticCast and CheckCXXCStyleCast, telling the caller if the function have created and applied a new cast node. I believe that this patch does what we need and is ready to be committed if you agree. It applies to r143190 (today) and passes the tests. > - Doug > Thanks, Nicola
cast.patch
Description: Binary data
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