Core: Guard vmlinux struct lookup against non-class metadata

_allocate_for_attribute reached for `metadata.__name__` whenever the
base symbol was not a known user struct, but `metadata` is only a struct
class for struct-typed symbols. For a symbol carrying None (any plainly
typed local) or a ctypes class (a `c_void_p` context parameter), that
raised AttributeError instead of reporting the unsupported access.

Resolve the name via getattr and fall through to the existing
"struct type not found" diagnostic when there is none.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: r41k0u

pythonbpf/allocation_pass.py

@@ -340,9 +340,15 @@ def _allocate_for_attribute(
 
     struct_type: type = local_sym_tab[struct_var].metadata
     if not struct_type or struct_type not in structs_sym_tab:
-        if VmlinuxHandlerRegistry.is_vmlinux_struct(struct_type.__name__):
+        # `metadata` only names a struct for struct-typed symbols. For anything
+        # else (None, an IR type, or a plain ctypes class such as a `c_void_p`
+        # context parameter) there is no vmlinux struct name to look up, so guard
+        # the attribute access instead of blowing up with an AttributeError.
+        vmlinux_struct_name = getattr(struct_type, "__name__", None)
+        if vmlinux_struct_name and VmlinuxHandlerRegistry.is_vmlinux_struct(
+            vmlinux_struct_name
+        ):
             # Handle vmlinux struct field access
-            vmlinux_struct_name = struct_type.__name__
             if not VmlinuxHandlerRegistry.has_field(vmlinux_struct_name, field_name):
                 logger.error(
                     f"Field '{field_name}' not found in vmlinux struct '{vmlinux_struct_name}'"