Per DWARF v5 Section 2.5.1.6, a nonzero DW_OP_convert operand references a type DIE in the current compilation unit, and that DIE must be a DW_TAG_base_type.
LLDB validates only the resolved DIE's size and encoding, not its tag. As a result, a non-base type DIE is accepted whenever it happens to carry base-type-like attributes — a DW_AT_byte_size/DW_AT_bit_size and a signed/unsigned DW_AT_encoding.
Source Evidence
The nonzero-operand path is Evaluate_DW_OP_convert in DWARFExpression.cpp, which resolves the target type through DWARFUnit::GetDIEBitSizeAndSign in DWARFUnit.cpp:
llvm::Expected<std::pair<uint64_t, bool>>
DWARFUnit::GetDIEBitSizeAndSign(uint64_t relative_die_offset) const {
const uint64_t abs_die_offset = relative_die_offset + GetOffset();
DWARFDIE die = const_cast<DWARFUnit *>(this)->GetDIE(abs_die_offset);
if (!die)
return llvm::createStringError("cannot resolve DW_OP_convert type DIE");
uint64_t encoding =
die.GetAttributeValueAsUnsigned(DW_AT_encoding, DW_ATE_hi_user);
uint64_t bit_size = die.GetAttributeValueAsUnsigned(DW_AT_byte_size, 0) * 8;
if (!bit_size)
bit_size = die.GetAttributeValueAsUnsigned(DW_AT_bit_size, 0);
if (!bit_size)
return llvm::createStringError("unsupported type size");
bool sign;
switch (encoding) {
case DW_ATE_signed:
case DW_ATE_signed_char:
sign = true;
break;
case DW_ATE_unsigned:
case DW_ATE_unsigned_char:
sign = false;
break;
default:
return llvm::createStringError("unsupported encoding");
}
return std::pair{bit_size, sign};
}It resolves the DIE and reads DW_AT_encoding, DW_AT_byte_size, and DW_AT_bit_size, but never checks that die.Tag() is DW_TAG_base_type. Any DIE carrying a signed/unsigned encoding and a size is therefore accepted. (A DIE without a signed/unsigned encoding falls into the default: unsupported encoding path, so the DIEs that slip through are exactly the non-base types that still have such an encoding and a size, such as DW_TAG_enumeration_type.)
Per DWARF v5 Section 2.5.1.6, a nonzero
DW_OP_convertoperand references a type DIE in the current compilation unit, and that DIE must be aDW_TAG_base_type.LLDB validates only the resolved DIE's size and encoding, not its tag. As a result, a non-base type DIE is accepted whenever it happens to carry base-type-like attributes — a
DW_AT_byte_size/DW_AT_bit_sizeand a signed/unsignedDW_AT_encoding.Source Evidence
The nonzero-operand path is
Evaluate_DW_OP_convertinDWARFExpression.cpp, which resolves the target type throughDWARFUnit::GetDIEBitSizeAndSigninDWARFUnit.cpp:It resolves the DIE and reads
DW_AT_encoding,DW_AT_byte_size, andDW_AT_bit_size, but never checks thatdie.Tag()isDW_TAG_base_type. Any DIE carrying a signed/unsigned encoding and a size is therefore accepted. (A DIE without a signed/unsigned encoding falls into thedefault: unsupported encodingpath, so the DIEs that slip through are exactly the non-base types that still have such an encoding and a size, such asDW_TAG_enumeration_type.)