https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113141
--- Comment #10 from Patrick Palka <ppalka at gcc dot gnu.org> --- The master branch has been updated by Jason Merrill <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:df7bfdb7dbf2d46aa5768a0280d4dcfcc868b7f9 commit r14-9947-df7bfdb7dbf2d46aa5768a0280d4dcfcc868b7f9 Author: Jason Merrill <ja...@redhat.com> Date: Wed Apr 10 15:12:26 2024 -0400 c++: reference cast, conversion fn [PR113141] The second testcase in 113141 is a separate issue: we first decide that the conversion is ill-formed, but then when recalculating the special c_cast_p handling makes us think it's OK. We don't want that, it should continue to fall back to the reinterpret_cast interpretation. And while we're here, let's warn that we're not using the conversion function. Note that the standard seems to say that in this case we should treat (Matrix &) as const_cast<Matrix &>(static_cast<const Matrix &>(X)), which would use the conversion operator, but that doesn't match existing practice, so let's resolve that another day. I've raised this issue with CWG; at the moment I lean toward never binding a temporary in a C-style cast to reference type, which would also be a change from existing practice. PR c++/113141 gcc/c-family/ChangeLog: * c.opt: Add -Wcast-user-defined. gcc/ChangeLog: * doc/invoke.texi: Document -Wcast-user-defined. gcc/cp/ChangeLog: * call.cc (reference_binding): For an invalid cast, warn and don't recalculate. gcc/testsuite/ChangeLog: * g++.dg/conversion/ref12.C: New test. Co-authored-by: Patrick Palka <ppa...@redhat.com>
