cor3ntin added inline comments.
================
Comment at: clang/lib/Sema/SemaDeclCXX.cpp:1905
+ if (SemaRef.LangOpts.CPlusPlus2b) {
+ if (!VD->getType()->isLiteralType(SemaRef.Context))
+ SemaRef.Diag(VD->getLocation(),
----------------
aaron.ballman wrote:
> aaron.ballman wrote:
> > cor3ntin wrote:
> > > hubert.reinterpretcast wrote:
> > > > This seems to trigger even when the type is dependent:
> > > > ```
> > > > <stdin>:1:36: warning: definition of a variable of non-literal type in
> > > > a constexpr function is incompatible with C++ standards before C++2b
> > > > [-Wpre-c++2b-compat]
> > > > auto qq = [](auto x) { decltype(x) n; };
> > > > ^
> > > > 1 warning generated.
> > > > ```
> > > >
> > > > This also seems to emit even when `Kind` is not
> > > > `Sema::CheckConstexprKind::Diagnose` (unlike the
> > > > `static`/`thread_local` case above). Is the `CheckLiteralType` logic
> > > > not reusable for this?
> > > You are right, thanks for noticing that, it was rather bogus.
> > > The reason I'm not using CheckLiteralType is to avoid duplicating a
> > > diagnostics message, as CheckLiteralType doesn't allow us to pass
> > > parameter to the diagnostic message.
> > >
> > > It leaves us with an uncovered scenario though: We do not emit the
> > > warning on template instantiation, and I don't think there is an easy
> > > way to do that.
> > > The reason I'm not using CheckLiteralType is to avoid duplicating a
> > > diagnostics message, as CheckLiteralType doesn't allow us to pass
> > > parameter to the diagnostic message.
> >
> > Huh?
> >
> > ```
> > static bool CheckLiteralType(Sema &SemaRef, Sema::CheckConstexprKind Kind,
> > SourceLocation Loc, QualType T, unsigned
> > DiagID,
> > Ts &&...DiagArgs) {
> > ...
> > }
> > ```
> > I would hope `DiagArgs` should do exactly that? :-)
> > It leaves us with an uncovered scenario though: We do not emit the warning
> > on template instantiation, and I don't think there is an easy way to do
> > that.
>
> I believe the code paths that lead us here all come from
> `Sema::CheckConstexprFunctionDefinition()` which is called from
> `Sema::ActOnFinishFunctionBody()` which seems to be called when instantiating
> templates in `Sema::InstantiateFunctionDefinition()`, so perhaps some more
> investigation is needed as to why we're not reaching this for template
> instantiations.
We could add something in addition of `Sema::CheckConstexprKind::CheckValid`
and `Sema::CheckConstexprKind::Diagnose`, but
* not for implicit lambdas, because we should not warn on lambdas that won't be
constexpr
* for explicit constexpr lambdas / functions, it would force us to call
CheckConstexprFunctionDefinition on instanciation, which we currently don't
do, and is not free for that one warning - and we would have to not-reemit the
other warnings. It seems like quite a fair amount of work for a diagnostic not
enabled by default.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D122249/new/
https://reviews.llvm.org/D122249
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