FYI, patch generally looks good. I think in two places you're needlessly checking for a reference type: the base type of a base initializer.
On Mon, Jun 20, 2011 at 10:07 AM, Manuel Klimek <[email protected]> wrote: > Changed to always require a type in ParenListExpr and tried to fill in the > right types (sanity checking welcome :) > > On Fri, Jun 17, 2011 at 9:15 AM, Douglas Gregor <[email protected]> wrote: > >> >> On Jun 17, 2011, at 8:11 AM, Douglas Gregor wrote: >> >> >> On Jun 16, 2011, at 11:47 PM, Manuel Klimek wrote: >> >> On Thu, Jun 16, 2011 at 11:36 PM, Douglas Gregor <[email protected]>wrote: >> >>> >>> On Jun 15, 2011, at 10:11 AM, Manuel Klimek wrote: >>> >>> On Tue, Jun 14, 2011 at 8:21 PM, Douglas Gregor <[email protected]>wrote: >>> >>>> >>>> On Jun 14, 2011, at 6:06 PM, Manuel Klimek wrote: >>>> >>>> > The attached patch >>>> > - fixes the introduction of null types for ParenListExpr's that end up >>>> > in the AST for explicit initializers by making the constructor of >>>> > ParenListExpr take a type (as suggested by dgregor on irc) >>>> > - gets rid of some code I assume is dead (tested by running the tests >>>> > and by running it over all of our internal C++ code without hitting >>>> > any of those asserts - and by my inability to come up with an example >>>> > that hits that code path (which admittedly doesn't mean a lot)) >>>> > - tested that the other in-use cases that create ParenListExpr's >>>> > without a type don't lead to them being in the AST in the end >>>> >>>> Index: lib/Sema/SemaDeclCXX.cpp >>>> diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp >>>> index >>>> ce99efbd0bd2020f702da71fc87a80d0b86759a8..a95ef69085526291eb7532aeb9788f68bab235f6 >>>> 100644 >>>> --- a/lib/Sema/SemaDeclCXX.cpp >>>> +++ b/lib/Sema/SemaDeclCXX.cpp >>>> @@ -1617,7 +1617,7 @@ Sema::BuildMemberInitializer(ValueDecl *Member, >>>> Expr **Args, >>>> // Can't check initialization for a member of dependent type or when >>>> // any of the arguments are type-dependent expressions. >>>> Init = new (Context) ParenListExpr(Context, LParenLoc, Args, >>>> NumArgs, >>>> - RParenLoc); >>>> + RParenLoc, QualType()); >>>> >>>> // Erase any temporaries within this evaluation context; we're not >>>> // going to track them in the AST, since we'll be rebuilding the >>>> >>>> Why not just use Member->getType() as the type of the ParenListExpr, so >>>> it never has a NULL type? >>>> >>> >>> Because I wasn't able to get it to make a difference, in which case I >>> default to not changing it. If you think the invariant should be that the >>> ParenListExpr always has a type, I'm happy to change this. I'll have a hard >>> time writing a test for it, though ... ;) >>> >>> >>> I just figured that if you're going to fix the problem in one place, it >>> would be better to just make it an AST invariant. >>> >>> >>>> Index: lib/Sema/SemaInit.cpp >>>> diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp >>>> index >>>> a33f5d0b2f3ef530c689a2ddc28ebaef3074635e..f0d39893a449e62902f21160f10bd6a400353789 >>>> 100644 >>>> --- a/lib/Sema/SemaInit.cpp >>>> +++ b/lib/Sema/SemaInit.cpp >>>> @@ -3684,19 +3684,9 @@ InitializationSequence::Perform(Sema &S, >>>> >>>> } >>>> } >>>> - >>>> - if (Kind.getKind() == InitializationKind::IK_Copy || >>>> Kind.isExplicitCast()) >>>> - return ExprResult(Args.release()[0]); >>>> - >>>> - if (Args.size() == 0) >>>> - return S.Owned((Expr *)0); >>>> - >>>> - unsigned NumArgs = Args.size(); >>>> - return S.Owned(new (S.Context) ParenListExpr(S.Context, >>>> - SourceLocation(), >>>> - (Expr >>>> **)Args.release(), >>>> - NumArgs, >>>> - SourceLocation())); >>>> + assert(Kind.getKind() == InitializationKind::IK_Copy || >>>> + Kind.isExplicitCast()); >>>> + return ExprResult(Args.release()[0]); >>>> } >>>> >>>> // No steps means no initialization. >>>> >>>> Hrm, interesting. This is only dead because its potential callers seem >>>> to avoid building InitializationSequences in dependent cases. Please update >>>> the assert to always check that Args.size() ==1, and if *that* doesn't >>>> trigger any failures, this change is okay. We can always resurrect the code >>>> if the callers change. >>>> >>> >>> I'm happy to do this, but I don't understand the underlying assumption >>> yet - even if Args.size() != 1, if the assert that I added is true, the code >>> will behave exactly the same way as before (before we would early return if >>> it is true). So I'm not sure what the extra assert would change (if it >>> breaks, and that makes the code wrong, I'd say the code was wrong before...) >>> >>> >>> The previous code would return *all* of the arguments in Args (NumArgs of >>> them) as a ParenListExpr, indicating direct initialization. >>> >>> The new code only returns the first of the arguments, so if we're going >>> to make that change, we need to assert that there is exactly one argument. >>> >> >> >> Now I feel like I'm really missing something here... >> In the previous code: >> >> if (Kind.getKind() == InitializationKind::IK_Copy || >>> Kind.isExplicitCast()) >>> return ExprResult(Args.release()[0]); >> >> >> ... reads to me as: >> if (condition) >> return statement; >> <... some code that was never executed ...> >> which I (at least hope that I did) transformed to: >> assert(condition); >> return statement; >> <... delete code that was never executed ...> >> which I would think is equivalent, given that the assert always holds >> true. >> >> What am I missing? >> >> >> The code that is currently never executed is still nonetheless correct, >> and a minor tweak the any of the callers' handling of initialization >> involving type-dependent expressions could make this code relevant again. If >> we take your simplification, and one of those tweaks happen, we'll silently >> transform ASTs into something semantically different and cause ourselves >> some serious debugging pain. >> >> So if you want to simplify this code, I'm asking you to add appropriate >> assertions to make sure that we catch the cases where this code will be >> broken. In particular, the code itself is designed to handle NumArgs != 1, >> but your simplification assumes NumArgs == 1 without checking. >> >> >> Apparently, I'm just misreading patches right now. This change is fine; >> sorry for the confusion. >> >> - Doug >> >> > > _______________________________________________ > cfe-commits mailing list > [email protected] > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits > >
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