On Sat, 24 Jan 2026, Nathaniel Shead wrote: > Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
LGTM too, this might also fix PR123354 (https://gcc.gnu.org/pipermail/gcc-patches/2026-January/705501.html) > > -- >8 -- > > What happens in the linked PR is that when evaluating the concept we > call 'push_to_top_level', we see cfun is non-null, and so call > 'push_function_context' which sets cfun to NULL and sets a flag so that > we remember to pop it later. > > Then, when instantiating Foo's default constructor as part of the > concept, we call 'maybe_push_to_top_level'. Here we see that 'Foo' is > function-local, so '!push_to_top', and we call 'push_function_context'. > This allocates a new cfun for some reason, and pushes that empty cfun. > > Eventually we 'maybe_pop_from_top_level', and restore that newly > allocated cfun (instead of a NULL cfun), which means that when we start > trying to build the new-expression (which requires building a statement > list) we try accessing the (uninitialized) cfun's x_stmt_tree rather > than the scope_chain's x_stmt_tree, and so crash. > > This fixes the issue by also remembering whether we had a cfun when > doing maybe_push_to_top_level so that we only do push_function_context > if needed. > > PR c++/123663 > > gcc/cp/ChangeLog: > > * name-lookup.cc (struct local_state_t): New flag has_cfun. > (local_state_t::save_and_clear): Set has_cfun, call > push_function_context iff there's a cfun to save. > (local_state_t::restore): call pop_function_context if > has_cfun is set. > (maybe_push_to_top_level): Delegte push_function_context to > local_state_t::save_and_clear. > (maybe_pop_from_top_level): Delegate pop_function_context to > local_state_t::restore. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp2a/concepts-pr123663.C: New test. > > Signed-off-by: Nathaniel Shead <[email protected]> > --- > gcc/cp/name-lookup.cc | 12 +++++++----- > gcc/testsuite/g++.dg/cpp2a/concepts-pr123663.C | 13 +++++++++++++ > 2 files changed, 20 insertions(+), 5 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-pr123663.C > > diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc > index 1b3713dc40e..10c45548dc2 100644 > --- a/gcc/cp/name-lookup.cc > +++ b/gcc/cp/name-lookup.cc > @@ -8957,6 +8957,7 @@ struct local_state_t > int cp_unevaluated_operand; > int c_inhibit_evaluation_warnings; > int cp_noexcept_operand_; > + bool has_cfun; > > static local_state_t > save_and_clear () > @@ -8968,6 +8969,9 @@ struct local_state_t > ::c_inhibit_evaluation_warnings = 0; > s.cp_noexcept_operand_ = ::cp_noexcept_operand; > ::cp_noexcept_operand = 0; > + s.has_cfun = !!cfun; > + if (s.has_cfun) > + push_function_context (); > return s; > } > > @@ -8977,6 +8981,8 @@ struct local_state_t > ::cp_unevaluated_operand = this->cp_unevaluated_operand; > ::c_inhibit_evaluation_warnings = this->c_inhibit_evaluation_warnings; > ::cp_noexcept_operand = this->cp_noexcept_operand_; > + if (this->has_cfun) > + pop_function_context (); > } > }; > > @@ -9005,7 +9011,6 @@ maybe_push_to_top_level (tree d) > else > { > gcc_assert (!processing_template_decl); > - push_function_context (); > local_state_stack.safe_push (local_state_t::save_and_clear ()); > } > > @@ -9020,10 +9025,7 @@ maybe_pop_from_top_level (bool push_to_top) > if (push_to_top) > pop_from_top_level (); > else > - { > - local_state_stack.pop ().restore (); > - pop_function_context (); > - } > + local_state_stack.pop ().restore (); > } > > /* Push into the scope of the namespace NS, even if it is deeply > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr123663.C > b/gcc/testsuite/g++.dg/cpp2a/concepts-pr123663.C > new file mode 100644 > index 00000000000..8ac303683c0 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr123663.C > @@ -0,0 +1,13 @@ > +// PR c++/123663 > +// { dg-do compile { target c++20 } } > + > +template <typename T> > +concept TestConcept = requires { > + new T[1]{}; > +}; > +struct base { > + base() { > + struct Foo {}; > + TestConcept<Foo>; > + } > +}; > -- > 2.51.0 > >
