bool ItaniumABILanguageRuntime::GetDynamicTypeAndAddress(
ValueObject &in_value, lldb::DynamicValueType use_dynamic,
TypeAndOrName &class_type_or_name, Address &dynamic_address,
Value::ValueType &value_type) {
// For Itanium, if the type has a vtable pointer in the object, it will be at
// offset 0
// in the object. That will point to the "address point" within the vtable
// (not the beginning of the
// vtable.) We can then look up the symbol containing this "address point"
// and that symbol's name
// demangled will contain the full class name.
// The second pointer above the "address point" is the "offset_to_top". We'll
// use that to get the
// start of the value object which holds the dynamic type.
//
class_type_or_name.Clear();
value_type = Value::ValueType::eValueTypeScalar;
// Only a pointer or reference type can have a different dynamic and static
// type:
if (CouldHaveDynamicValue(in_value)) {
// First job, pull out the address at 0 offset from the object.
AddressType address_type;
lldb::addr_t original_ptr = in_value.GetPointerValue(&address_type);
if (original_ptr == LLDB_INVALID_ADDRESS)
return false;
ExecutionContext exe_ctx(in_value.GetExecutionContextRef());
Process *process = exe_ctx.GetProcessPtr();
if (process == nullptr)
return false;
Error error;
const lldb::addr_t vtable_address_point =
process->ReadPointerFromMemory(original_ptr, error);
if (!error.Success() || vtable_address_point == LLDB_INVALID_ADDRESS) {
return false;
}
class_type_or_name = GetTypeInfoFromVTableAddress(in_value, original_ptr,
vtable_address_point);
if (class_type_or_name) {
TypeSP type_sp = class_type_or_name.GetTypeSP();
// There can only be one type with a given name,
// so we've just found duplicate definitions, and this
// one will do as well as any other.
// We don't consider something to have a dynamic type if
// it is the same as the static type. So compare against
// the value we were handed.
if (type_sp) {
if (ClangASTContext::AreTypesSame(in_value.GetCompilerType(),
type_sp->GetForwardCompilerType())) {
// The dynamic type we found was the same type,
// so we don't have a dynamic type here...
return false;
}
// The offset_to_top is two pointers above the vtable pointer.
const uint32_t addr_byte_size = process->GetAddressByteSize();
const lldb::addr_t offset_to_top_location =
vtable_address_point - 2 * addr_byte_size;
// Watch for underflow, offset_to_top_location should be less than
// vtable_address_point
if (offset_to_top_location >= vtable_address_point)
return false;
const int64_t offset_to_top = process->ReadSignedIntegerFromMemory(
offset_to_top_location, addr_byte_size, INT64_MIN, error);
if (offset_to_top == INT64_MIN)
return false;
// So the dynamic type is a value that starts at offset_to_top
// above the original address.
lldb::addr_t dynamic_addr = original_ptr + offset_to_top;
if (!process->GetTarget().GetSectionLoadList().ResolveLoadAddress(
dynamic_addr, dynamic_address)) {
dynamic_address.SetRawAddress(dynamic_addr);
}
return true;
}
}
}
return class_type_or_name.IsEmpty() == false;
}
