[PATCH] D147591: [clang][Interp] Handle CXXTemporaryObjectExprs

[Timm Bäder via Phabricator via cfe-commits]

tbaeder added inline comments.


================
Comment at: clang/test/AST/Interp/records.cpp:317-318
     {
-      auto T = Test(Arr, Pos);
+      Test(Arr, Pos);
       // End of scope, should destroy Test.
     }
----------------
aaron.ballman wrote:
> tbaeder wrote:
> > aaron.ballman wrote:
> > > Nit: nothing actually tests that this object is destroyed correctly. Here's an interesting test to consider:
> > > ```
> > > struct S {
> > >   constexpr S() {}
> > >   constexpr ~S() noexcept(false) { throw 12; }
> > > };
> > > 
> > > constexpr int f() {
> > >   S{};
> > >   return 12;
> > > }
> > > 
> > > static_assert(f() == 12);
> > > ```
> > > That should fail because `~S()` would hit the `throw` expression and thus is not valid. Note, you'll need to add `-Wno-invalid-constexpr` to your test to avoid the warning-defaults-to-error about the destructor never producing a constant expression.
> > There are multiple reasons why that sample is not rejected right now, one I can easily fix in a follow-up patch, the other one would actually require us to recognize the `throw` and reject it with a proper diagnostic.
> We should definitely fix the `throw` at some point, but any of the dynamically reachable problematic constructs would work (`dynamic_cast` whose type would throw, invocation of the `va_arg` macro, `reinterpret_cast`, etc)
Yes, I think we need a new opcode for that so we only emit the diagnostic when such a construct is actually executed.


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D147591/new/

https://reviews.llvm.org/D147591