On Tue, Aug 18, 2015 at 2:03 PM, David Blaikie <dblai...@gmail.com> wrote:
> Richard, do you think there's anything we could do better here? > > It seems difficult to support proper move semantic behavior for > [Sema]DiagnosticBuilder across the two common use cases: > > DiagnosticBuilder D; > D << x; > D << y; > return D; > > and > > return DiagnosticBuilder() << x << y; > Do we actually use this form to return a DiagnosticBuilder, or just to construct an ActionResult? Can we eliminate uses of this form? > The only thing I can imagine is if every one of those op<< were function > templates using universal references (I forget, is that the right name for > them?) and matching their return value (so in the first case, passed a > non-const lvalue ref, they return by non-const lvalue ref, and in the > second case, passed an rvalue, they return the same). But that seems > painful. > It seems tricky to form an unambiguous overload set for this that preserves the value category, without duplicating all the operator<<s. > On Tue, Aug 18, 2015 at 1:54 PM, David Blaikie via cfe-commits < > cfe-commits@lists.llvm.org> wrote: > >> Author: dblaikie >> Date: Tue Aug 18 15:54:26 2015 >> New Revision: 245352 >> >> URL: http://llvm.org/viewvc/llvm-project?rev=245352&view=rev >> Log: >> Workaround -Wdeprecated on SemDiagnosticConsumer's tricksy copy ctor. >> >> Modified: >> cfe/trunk/include/clang/Sema/Sema.h >> >> Modified: cfe/trunk/include/clang/Sema/Sema.h >> URL: >> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=245352&r1=245351&r2=245352&view=diff >> >> ============================================================================== >> --- cfe/trunk/include/clang/Sema/Sema.h (original) >> +++ cfe/trunk/include/clang/Sema/Sema.h Tue Aug 18 15:54:26 2015 >> @@ -1054,6 +1054,14 @@ public: >> SemaDiagnosticBuilder(DiagnosticBuilder &DB, Sema &SemaRef, unsigned >> DiagID) >> : DiagnosticBuilder(DB), SemaRef(SemaRef), DiagID(DiagID) { } >> >> + // This is a cunning lie. DiagnosticBuilder actually performs move >> + // construction in its copy constructor (but due to varied uses, >> it's not >> + // possible to conveniently express this as actual move >> construction). So >> + // the default copy ctor here is fine, because the base class >> disables the >> + // source anyway, so the user-defined ~SemaDiagnosticBuilder is a >> safe no-op >> + // in that case anwyay. >> + SemaDiagnosticBuilder(const SemaDiagnosticBuilder&) = default; >> + >> ~SemaDiagnosticBuilder() { >> // If we aren't active, there is nothing to do. >> if (!isActive()) return; >> >> >> _______________________________________________ >> cfe-commits mailing list >> cfe-commits@lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits >> > >
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