================
@@ -2243,9 +2236,27 @@
ItaniumRecordLayoutBuilder::updateExternalFieldOffset(const FieldDecl *Field,
uint64_t ComputedOffset)
{
uint64_t ExternalFieldOffset = External.getExternalFieldOffset(Field);
- if (InferAlignment && ExternalFieldOffset < ComputedOffset) {
- // The externally-supplied field offset is before the field offset we
- // computed. Assume that the structure is packed.
+ // DWARF doesn't tell us whether a structure was declared as packed.
+ // So we try to figure out if the supplied Field is at a packed offset
+ // (i.e., the externally-supplied offset is less than the layout builder
+ // expected).
+ //
+ // There are cases where fields are placed at overlapping offsets (e.g.,
+ // as a result of [[no_unique_address]]). In those cases we don't want
+ // to incorrectly deduce that they are placed at packed offsets. Hence,
+ // ignore empty fields (which are the only fields that can overlap).
+ //
+ // FIXME: emit enough information in DWARF to get rid of InferAlignment.
+ //
+ CXXRecordDecl *CXX = nullptr;
+ if (auto *RT = dyn_cast<RecordType>(Field->getType()))
+ CXX = RT->getAsCXXRecordDecl();
----------------
rjmccall wrote:
This is all just `auto CXX = Field->getType()->getAsCXXRecordDecl();`
https://github.com/llvm/llvm-project/pull/97443
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