aaron.ballman added inline comments.
================
Comment at: clang/include/clang/Parse/Parser.h:2311
case DeclSpecContext::DSC_association:
+ case DeclSpecContext::DSC_offsetof:
return true;
----------------
inclyc wrote:
> aaron.ballman wrote:
> > Is this correct? I don't think we can deduce the type from `offsetof`
> > through CTAD, can we?
> >
> > https://godbolt.org/z/Kab6ahYe7
> >
> > (This might be a good test case to add assuming we don't already have that
> > coverage.)
> Emm, these checks just return as the same as "type_specifier". Because that's
> what we passed into "ParsingTypename" before.
Hmmm, that's certainly reasonable. Can you add the test case and make sure the
behavior doesn't change?
================
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:
> > 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....
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D133574/new/
https://reviews.llvm.org/D133574
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