inclyc added inline comments.
================
Comment at: clang/test/Sema/offsetof.c:79
+ int a;
+ struct B // no-error, struct B is not defined within __builtin_offsetof
directly
+ {
----------------
inclyc wrote:
> aaron.ballman wrote:
> > inclyc wrote:
> > > aaron.ballman wrote:
> > > > I think this is defensible. The wording in the standard is "If the
> > > > specified type defines a new type or if the specified member is a
> > > > bit-field, the behavior is undefined." and the specified type in this
> > > > case is `struct A`; that `struct A` happens to also define `struct B`
> > > > is immaterial.
> > > >
> > > > However, the intent behind the change to the rule is to support older
> > > > implementations of `offsetof` to protect them from having to deal with
> > > > a case like: `offsetof(struct S { int a, b }, b);` where `offsetof` is
> > > > a macro and thus the comma between `a` and `b` is treated as a
> > > > separator. So there's a part of me that wonders if we want to also
> > > > support diagnosing this case. But then we'd have to look at the
> > > > declarator context more recursively to see whether any of the contexts
> > > > on the stack are an `offsetof` context and that might be tricky.
> > > >
> > > > Thoughts?
> > > FWIW, gcc seems just rejects all definitions in this context. (Perhaps
> > > during Parsing the statements). If we add a bool state to the Parser
> > > (just using RAII object as before) struct B will trigger diagnostic error
> > > because the state "ParsingOffsetof" is passed into inner declaration.
> > GCC accepts currently: https://godbolt.org/z/oEvzjW6Ee but you're correct
> > regarding switching back to an RAII object being an easier way to address
> > the nested declarations.
> >
> > Let me think on this situation a bit....
> > GCC accepts currently
>
> C++: https://godbolt.org/z/fon8e7dzf
```
<source>: In function 'int main()':
<source>:3:3: error: types may not be defined within '__builtin_offsetof'
3 | {
| ^
<source>:6:5: error: types may not be defined within '__builtin_offsetof'
6 | {
| ^
Compiler returned: 1
```
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D133574/new/
https://reviews.llvm.org/D133574
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