properly fixes the LLDB pretty printer

Author: cjdb

lldb/examples/synthetic/libcxx.py

@@ -104,12 +104,24 @@ def get_buffer_endcap(parent, buffer, begin, has_compressed_pair_layout, is_size
         map_endcap = parent._get_value_of_compressed_pair(
             buffer.GetChildMemberWithName("__end_cap_")
         )
+    elif buffer.GetType().GetNumberOfDirectBaseClasses() == 1:
+        # LLVM 22's __split_buffer is derived from a base class that describes its layout. When the
+        # compressed pair ABI is required, we also use an anonymous struct. Per [#158131], LLDB
+        # is unable to access members of an anonymous struct to a base class, through the derived
+        # class. This means that in order to access the compressed pair's pointer, we need to first
+        # get to its base class.
+        #
+        # [#158131]: https://github.com/llvm/llvm-project/issues/158131
+        buffer = buffer.GetChildAtIndex(0)
+        if is_size_based:
+            map_endcap = buffer.GetChildMemberWithName("__cap_")
+        else:
+            map_endcap = buffer.GetChildMemberWithName("__back_cap_")
+        map_endcap = map_endcap.GetValueAsUnsigned(0)
     else:
         map_endcap = buffer.GetChildMemberWithName("__cap_")
         if not map_endcap.IsValid():
             map_endcap = buffer.GetChildMemberWithName("__end_cap_")
-        if not map_endcap.IsValid():
-            map_endcap = buffer.GetChildMemberWithName("__back_cap_")
         map_endcap = map_endcap.GetValueAsUnsigned(0)
 
     if is_size_based:
@@ -804,11 +816,11 @@ def update(self):
             map_ = self.valobj.GetChildMemberWithName("__map_")
             is_size_based = map_.GetChildMemberWithName("__size_").IsValid()
             first = map_.GetChildMemberWithName("__first_")
+            # LLVM 22 renames __map_.__begin_ to __map_.__front_cap_
+            if not first:
+                first = map_.GetChildMemberWithName("__front_cap_")
             map_first = first.GetValueAsUnsigned(0)
             self.map_begin = map_.GetChildMemberWithName("__begin_")
-            # LLVM 22 renames __map_.__begin_ to __map_.__front_cap_
-            if not self.map_begin:
-                self.map_begin = map_.GetChildMemberWithName("__front_cap_")
             map_begin = self.map_begin.GetValueAsUnsigned(0)
             map_end = get_buffer_end(map_, map_begin)
             map_endcap = get_buffer_endcap(