Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/15?
-- >8 --
In my r15-6792 patch I added a call to tsubst in tsubst_pack_index
to fully instantiate args#N in the pack.
Here we are in an unevaluated context, but since the pack is
a TREE_VEC, we call tsubst_template_args which has cp_evaluated
at the beginning. That causes a crash because we trip on the
assert in tsubst_expr/PARM_DECL:
gcc_assert (cp_unevaluated_operand);
because retrieve_local_specialization didn't find anything (becase
there are no local_specializations yet).
ISTM that we don't need a full instantiation in an unevaluated context
so we can avoid the crash like this.
PR c++/121325
gcc/cp/ChangeLog:
* pt.cc (tsubst_pack_index): Don't call tsubst in an unevaluated
context.
gcc/testsuite/ChangeLog:
* g++.dg/cpp26/pack-indexing18.C: New test.
---
gcc/cp/pt.cc | 7 +++--
gcc/testsuite/g++.dg/cpp26/pack-indexing18.C | 32 ++++++++++++++++++++
2 files changed, 37 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp26/pack-indexing18.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c418edc6931..1e3cb6ac32d 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -14215,11 +14215,14 @@ tsubst_pack_index (tree t, tree args, tsubst_flags_t
complain, tree in_decl)
tree pack = PACK_INDEX_PACK (t);
if (PACK_EXPANSION_P (pack))
pack = tsubst_pack_expansion (pack, args, complain, in_decl);
- else
+ else if (!cp_unevaluated_operand)
{
/* PACK can be {*args#0} whose args#0's value-expr refers to
a partially instantiated closure. Let tsubst find the
- fully-instantiated one. */
+ fully-instantiated one. In an unevaluated context we don't
+ call this because tsubst_template_args switches back to
+ evaluated context immediately, and we may have parameters
+ without local specializations. */
gcc_assert (TREE_CODE (pack) == TREE_VEC);
pack = tsubst (pack, args, complain, in_decl);
}
diff --git a/gcc/testsuite/g++.dg/cpp26/pack-indexing18.C
b/gcc/testsuite/g++.dg/cpp26/pack-indexing18.C
new file mode 100644
index 00000000000..d3e3730408c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp26/pack-indexing18.C
@@ -0,0 +1,32 @@
+// PR c++/121325
+// { dg-do compile { target c++26 } }
+
+void f(auto... a) requires requires { []<int i = 0>
noexcept(noexcept(a...[i])) { }(); } {}
+void g(auto... a) requires requires { []<int i = 0> {
static_assert(noexcept(a...[i])); }(); } {}
+
+void
+h ()
+{
+ f (0);
+ g (0);
+}
+
+void foo () {}
+void bar () noexcept {}
+template<bool B>
+void baz () noexcept(B) {}
+
+template<typename... Ts>
+void
+x (Ts... ts) noexcept (noexcept (ts...[0]()))
+{
+}
+
+void
+y ()
+{
+ static_assert (!noexcept (x (foo)));
+ static_assert (noexcept (x (bar)));
+ static_assert (noexcept (x (baz<true>)));
+ static_assert (!noexcept (x (baz<false>)));
+}
base-commit: a2f4b0466be29c853c32498ae49c1acfa1594f30
--
2.51.1
