rust-lang/rust · error · Exception

Cannot bless invalid SBType object

Error message

Cannot bless invalid SBType object

What it means

Raised by from_lldb.type_from_lldb during a bless run when an lldb.SBType fails IsValid(). The function needs to read byte size, basic type, type class, fields and generics, none of which are meaningful on an invalid type, so blessing is aborted.

Source

Thrown at src/etc/lldb_batchmode/from_lldb.py:225

    # template values at the moment.
    # Eventually we can either change `get_template_args` to skip template values OR update
    # rustc to output them for DWARF debug info. Also, since it's target-specific behavior, it
    # shouldn't actually cause tests not to work.
    if TARGET == Target.WindowsMsvc:
        return [
            lldb_lookup.resolve_msvc_template_arg(x, sbtarget)
            for x in lldb_lookup.get_template_args(name)
        ]
    else:
        return [
            ty.GetTemplateArgumentType(i)
            for i in range(ty.GetNumberOfTemplateArguments())
        ]


def type_from_lldb(ty: lldb.SBType, sbtarget: lldb.SBTarget) -> Type:
    if BLESS and not ty.IsValid():
        raise Exception("Cannot bless invalid SBType object")

    generic_types = get_generics(ty, sbtarget)
    generics = [g.GetName() for g in generic_types]

    return Type(
        ty.GetByteSize(),
        ty.GetBasicType(),
        ty.GetTypeClass(),
        [field_from_lldb(ty.GetFieldAtIndex(i)) for i in range(ty.GetNumberOfFields())],
        generics,
    )


def child_from_lldb(child: lldb.SBValue) -> Child:
    if BLESS and not child.IsValid():
        raise Exception("Cannot bless invalid child")

    sbtype: lldb.SBType = child.GetType()

View on GitHub (pinned to 7088e4b63a)

Solutions

1. Verify the SBType is valid in an interactive LLDB session before blessing (script print(ty.IsValid())).
2. For PDB targets, ensure get_generics falls back to lldb_lookup.resolve_msvc_template_arg correctly and the template arg name is parseable.
3. Recompile with DWARF debug info on non-MSVC targets to sidestep PDB template-arg gaps.

Example fix

# before: blindly iterating template args that may be unresolved
for i in range(ty.GetNumberOfTemplateArguments()):
    type_from_lldb(ty.GetTemplateArgumentType(i), target)
# after: guard each arg
for i in range(ty.GetNumberOfTemplateArguments()):
    arg = ty.GetTemplateArgumentType(i)
    if arg.IsValid():
        type_from_lldb(arg, target)

if BLESS:
    for i in range(ty.GetNumberOfTemplateArguments()):
        arg = ty.GetTemplateArgumentType(i)
        if not arg.IsValid():
            continue  # or raise a clearer, arg-indexed error

def is_valid_type(ty: lldb.SBType) -> bool:
    return ty.IsValid()

When it happens

Trigger: Calling type_from_lldb with BLESS=True on an SBType obtained from e.g. GetTemplateArgumentType(i) that LLDB could not resolve (common with PDB/MSVC where template args are synthesized), or from a dangling SBType after the target's type system changed.

Common situations: MSVC/PDB targets where template argument types are not represented; a generic type's argument fails to resolve; LLDB/clang version regression in type lookup.

Related errors

• Invalid input data path: '{path}'\nIf test data has not been
• Cannot bless invalid SBTypeMember object
• Cannot bless invalid child
• Cannot bless invalid SBValue object
• <bless error: Cannot find variable {var_name}>

AI-assisted analysis of rust-lang/rust@7088e4b63a (2026-08-10). Data as JSON: /api/errors/1142f6852addaf6d. Report an issue: GitHub.