PiJoules wrote:
I updated to this with a new AST node but would like some guidance in
implementation details. One of the shortcomings of making this a (sugared) node
is when passing this type around through templates, the node doesn't persist
since only canonical types are substituted through templates. This could lead
to something like:
```
void func() __attribute__((cfi_unchecked_callee)) {}
template <typename T>
struct S {
S(T *ptr) {}
};
S s(&func);
```
Giving a warning since clang deduces `T *ptr` as the canonical `void (*)()`.
Other attributes like `noreturn` work around this by being part of the function
prototype via `ExtInfo` or `FunctionTypeExtraBitfields` as @efriedma-quic
suggested, but using the bitfields alone wouldn't allow warning on casts since
those attrributes get freely added/dropped without warning. I think perhaps the
best way to approach this would be instead treating this as an extra bitfield
rather than having a node and for every implicit conversion which would add or
drop attributes, specifically check if this attribute is dropped. I'd like some
opinions on this before moving forward though just to make sure I don't do
unnecessary work. I imagine we wouldn't want a mix of both a node and extra
bitfield since we'd have two representations of the same thing. Another idea is
perhaps making this not a sugared type, but I don't know if there would be
ramifications to that.
https://github.com/llvm/llvm-project/pull/135836
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