teemperor added a comment.
> (and it could tell clang exactly how large the structure is too - from the
> DWARF)
We are actually doing that to my knowledge and return the `DW_AT_byte_size`
value for the record type. The relevant API that LLDB implements to get
layout/size info back to Clang is:
bool layoutRecordType(
const clang::RecordDecl *Record, uint64_t &Size, uint64_t &Alignment,
llvm::DenseMap<const clang::FieldDecl *, uint64_t> &FieldOffsets,
llvm::DenseMap<const clang::CXXRecordDecl *, clang::CharUnits>
&BaseOffsets,
llvm::DenseMap<const clang::CXXRecordDecl *, clang::CharUnits>
&VirtualBaseOffsets) override;
I think the `sizeof` part actually works* in this regard as we just return
whatever we got from DWARF. I get the correct results for the example above
(both with and without this patch). There might be some weirder corner cases
that could go wrong but I think the main concern are more complicated
situations like in the crash that is fixed here.
FWIW, I took a look at the DWARF standard and I think that is actually
something we should already emit in the form of a `DW_AT_byte_size 0` attribute
at the field? Quote:
If the size of a data member is not the same as the size of the type given
for the data member, the data member has either a DW_AT_byte_size or a
DW_AT_bit_size attribute whose integer constant value (see Section 2.19) is the
amount of storage needed to hold the value of the data member.
I am not a DWARF laywer so maybe I understand that part wrong.
(*I actually found a bug that miscalculated empty structs while testing, but
that's unrelated. Patch incoming).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D101237/new/
https://reviews.llvm.org/D101237
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