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f74aaca632
**Background** Prior to DWARFv4, there was no clear normative text on how to handle static data members. Non-normative text suggested that compilers should use `DW_AT_external` to mark static data members of structrues/unions. Clang does this consistently. However, GCC doesn't, e.g., when the structure/union is in an anonymous namespace (which is C++ standard conformant). Additionally, GCC never emits `DW_AT_data_member_location`s for union members (regardless of storage linkage and storage duration). Since DWARFv5 (issue 161118.1), static data members get emitted as `DW_TAG_variable`. LLDB used to differentiate between static and non-static members by checking the `DW_AT_external` flag and the absence of `DW_AT_data_member_location`. With [D18008](https://reviews.llvm.org/D18008) LLDB started to pretend that union members always have a `0` `DW_AT_data_member_location` by default (because GCC never emits these locations). In [D124409](https://reviews.llvm.org/D124409) LLDB stopped checking the `DW_AT_external` flag to account for the case where GCC doesn't emit the flag for types in anonymous namespaces; instead we only check for presence of `DW_AT_data_member_location`s. The combination of these changes then meant that LLDB would never correctly detect that a union has static data members. **Solution** Instead of unconditionally initializing the `member_byte_offset` to `0` specifically for union members, this patch proposes to check for both the absence of `DW_AT_data_member_location` and `DW_AT_declaration`, which consistently gets emitted for static data members on GCC and Clang. We initialize the `member_byte_offset` to `0` anyway if we determine it wasn't a static. So removing the special case for unions makes this code simpler to reason about. Long-term, we should just use DWARFv5's new representation for static data members. Fixes #68135 |
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