nomanous added inline comments.
================
Comment at: clang/lib/Sema/SemaTemplate.cpp:10117
+ TSK == TSK_ExplicitInstantiationDefinition && Prev &&
+ !Context.hasSameTypeIgnoreLifetime(Prev->getType(), R)) {
+ Diag(T->getTypeLoc().getBeginLoc(),
----------------
nomanous wrote:
> rsmith wrote:
> > Please can you point us at an example that needs this "ignore lifetime"
> > nuance? We should check with Apple folks what they want to happen here, and
> > we should presumably have the same rule for all explicit instantiations of
> > templated variables -- both in the static data member case here and the
> > variable template case a few lines above.
> >
> > My expectation is that we want one of these two rules:
> > 1) the declared lifetime should match exactly between the declaration and
> > the explicit instantiation, or
> > 2) there cannot be a declared lifetime on the explicit instantiation, and a
> > lifetime on the template declaration is ignored by the check
> > (or a combination of these rules where we accept either option). I don't
> > think that matches what you're doing here -- in particular, I think a wrong
> > declared lifetime on the explicit instantiation should result in an error.
> I'll do some test and give you a code snippet to trigger the lifetime
> mismatch when lifetime specifiers are not ignored.
With lifetime specifiers not ignored, use command
```
clang -cc1 -fobjc-arc -fblocks -fsyntax-only snippet.mm
```
to compile the obj-c++ file `snippet.mm` whose contents are as follows:
```
typedef void (^fptr)();
template<typename T> struct StaticMembers {
static fptr f;
};
template<typename T>
fptr StaticMembers<T>::f = [] {};
template fptr StaticMembers<float>::f;
```
The compiler will give a type mismatch error, saying that `f`'s definition in
the template class has a type `'__strong fptr' (aka 'void (^__strong)()')`
while its explicit instantiation has a type `'fptr' (aka 'void (^)()')`, though
they should essentially have the same type.
This problem only happens in explicit instantiation of a static member of block
type and doesn't affect static members of other types.
@rsmith
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D90448/new/
https://reviews.llvm.org/D90448
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