https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94772
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:64da1b761db248f4f0d2235a6055c025fbbc94eb commit r10-7996-g64da1b761db248f4f0d2235a6055c025fbbc94eb Author: Patrick Palka <ppa...@redhat.com> Date: Mon Apr 27 17:06:35 2020 -0400 c++: Delegating constructor in constexpr init [PR94772] In the first testcase below, the call to the target constructor foo{} from foo's delegating constructor is encoded as the INIT_EXPR *(struct foo *) this = AGGR_INIT_EXPR <4, __ct_comp, D.2140, ...>; During initialization of the variable 'bar', we prematurely set TREE_READONLY on bar's CONSTRUCTOR in two places before the outer delegating constructor has returned: first, at the end of cxx_eval_call_expression after evaluating the RHS of the above INIT_EXPR, and second, at the end of cxx_eval_store_expression after having finished evaluating the above INIT_EXPR. This then prevents the rest of the outer delegating constructor from mutating 'bar'. This (hopefully minimally risky) patch makes cxx_eval_call_expression refrain from setting TREE_READONLY when evaluating the target constructor of a delegating constructor. It also makes cxx_eval_store_expression refrain from setting TREE_READONLY when the object being initialized is "*this', on the basis that it should be the responsibility of the routine that set 'this' in the first place to set the object's TREE_READONLY appropriately. gcc/cp/ChangeLog: PR c++/94772 * constexpr.c (cxx_eval_call_expression): Don't set new_obj if we're evaluating the target constructor of a delegating constructor. (cxx_eval_store_expression): Don't set TREE_READONLY if the LHS of the INIT_EXPR is '*this'. gcc/testsuite/ChangeLog: PR c++/94772 * g++.dg/cpp1y/constexpr-tracking-const23.C: New test. * g++.dg/cpp1y/constexpr-tracking-const24.C: New test. * g++.dg/cpp1y/constexpr-tracking-const25.C: New test.
