[Lldb-commits] [lldb] [lldb][DWARFUnit] Implement PeekDIEName query (PR #78486)

[Greg Clayton via lldb-commits]

================
@@ -663,6 +663,14 @@ DWARFUnit::GetDIE(dw_offset_t die_offset) {
   return DWARFDIE(); // Not found
 }
 
+llvm::StringRef DWARFUnit::PeekDIEName(dw_offset_t die_offset) {
+  const DWARFDataExtractor &data = GetData();
+  DWARFDebugInfoEntry die;
+  if (!die.Extract(data, this, &die_offset))
+    return llvm::StringRef();
+  return die.GetName(this);
+}
----------------
clayborg wrote:

If the attribute isn't in the current DIE (it is in a `DW_AT_specification` or `DW_AT_abstract_origin`), the `DWARFDebugInfoEntry::GetAttributeValue(...)` function will just run this code:
```
    if (GetAttributeValue(cu, DW_AT_specification, form_value)) {
      DWARFDIE die = form_value.Reference();
      if (die) {
```
or
```
    if (GetAttributeValue(cu, DW_AT_abstract_origin, form_value)) {
      DWARFDIE die = form_value.Reference();
      if (die) {
```
Both of these go back to the DWARFDIE class which will cause all of the DIEs to be parsed in the DWARFUnit anyway. So the peek function will work, it will just do a lot more work than you expected. Note that if the `DW_AT_specification` or `DW_AT_abstract_origin` attributes can represent a DIE from another compile unit of they use the `DW_FORM_ref_addr`, which can point across compile units. So it will take some more work to make the `DWARFUnit::PeekDIEName` work and be as efficient as needed.

https://github.com/llvm/llvm-project/pull/78486