rjmccall added inline comments.
================
Comment at: clang/lib/AST/ItaniumMangle.cpp:5576
+ "program to refer to the anonymous union, and there is therefore no need
"
+ "to mangle its name. '");
+}
----------------
erichkeane wrote:
> rjmccall wrote:
> > Unfortunately, I think class value mangling has a counter-example to this:
> > you can have an anonymous struct or union which doesn't declare any named
> > members but will of course nonetheless show up in the list of members in
> > the enclosing class. Code can even give it a non-zero initializer using
> > list-initialization; that value can never be read, but it's there, and
> > presumably it's part of uniquely determining a different template argument
> > value and therefore needs to be mangled.
> >
> > I don't know what we should do about this in the ABI, but we shouldn't
> > crash in the compiler.
> I'm not really understanding what you mean? Can you provide an example? All
> of the cases I could come up with like this ended up getting caught by the
> 'zero -init' case.
>
> That said, I considered this 'unreachable' to be a distinct improvement over
> our current behavior which is to crash at effectively line 5558.
>
> Would you prefer some sort of 'fatal-error' emit here?
I think the test case would be something like:
```
struct A {
union { unsigned: 10; };
int x;
constexpr A(int x) : x(x) {}
};
template <A a> void foo() {}
template void foo<A(5)>();
```
But also consider:
```
struct B {
struct Nested {
union { unsigned: 10; };
int x;
} nested;
constexpr B(int x) : nested{5, x} {}
};
template <B b> void bar() {}
template void bar<B(10)>();
```
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D122820/new/
https://reviews.llvm.org/D122820
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