On 10/24/23 12:18, Marek Polacek wrote:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?-- >8 -- Here we issue a bogus error: invalid operands of types 'unsigned char:2' and 'int' to binary 'operator!=' when casting a bit-field of scoped enum type to bool. In build_static_cast_1, perform_direct_initialization_if_possible returns NULL_TREE, because the invented declaration T t(e) fails, which is correct. So we go down to ocp_convert, which has code to deal with this case: /* We can't implicitly convert a scoped enum to bool, so convert to the underlying type first. */ if (SCOPED_ENUM_P (intype) && (convtype & CONV_STATIC)) e = build_nop (ENUM_UNDERLYING_TYPE (intype), e); but the SCOPED_ENUM_P is false since intype is <unnamed-unsigned:2>. This could be fixed by using unlowered_expr_type. But then c_common_truthvalue_conversion/CASE_CONVERT has a similar problem, and unlowered_expr_type is a C++-only function. Rather than adding a dummy unlowered_expr_type to C, I think we should follow [expr.static.cast]p3: "the lvalue-to-rvalue conversion is applied to the bit-field and the resulting prvalue is used as the operand of the static_cast." There are no prvalue bit-fields, so the l-to-r conversion will get us an expression whose type is the enum. (I thought we didn't need decay_conversion because that does a whole lot more but using it would make sense to me too.)
It's possible that we might want some of that more, particularly mark_rvalue_use; decay_conversion seems like the right answer. OK with that change.
rvalue() would also make sense, though that seems to be missing a call to unlowered_expr_type at the moment. In fact, after "otherwise, it's the lvalue-to-rvalue conversion" in decay_conv should probably just be a call to rvalue, with missing bits added to the latter function.
Jason
