On 12/22/22 11:31, Patrick Palka wrote:
On Wed, 21 Dec 2022, Jason Merrill wrote:
On 12/21/22 09:52, Patrick Palka wrote:
Here during ahead of time checking of C{}, we indirectly call get_nsdmi
for C::m from finish_compound_literal, which in turn calls
break_out_target_exprs for C::m's (non-templated) initializer, during
which we end up building a call to A::~A and checking expr_noexcept_p
for it (from build_vec_delete_1). But this is all done with
processing_template_decl set, so the built A::~A call is templated
(whose form r12-6897-gdec8d0e5fa00ceb2 recently changed) which
expr_noexcept_p doesn't expect and we crash.
In r10-6183-g20afdcd3698275 we fixed a similar issue by guarding a
expr_noexcept_p call with !processing_template_decl, which works here
too. But it seems to me since the initializer we obtain in get_nsdmi is
always non-templated, it should be calling break_out_target_exprs with
processing_template_decl cleared since otherwise the function might end
up mixing templated and non-templated trees.
I'm not sure about this though, perhaps this is not the best fix here.
Alternatively, when processing_template_decl we could make get_nsdmi
avoid calling break_out_target_exprs at all or something. Additionally,
perhaps break_out_target_exprs should be a no-op more generally when
processing_template_decl since we shouldn't see any TARGET_EXPRs inside
a template?
Hmm.
Any time we would call break_out_target_exprs we're dealing with non-dependent
expressions; if we're in a template, we're building up an initializer or a
call that we'll soon throw away, just for the purpose of checking or type
computation.
Furthermore, as you say, the argument is always a non-template tree, whether
in get_nsdmi or convert_default_arg. So having processing_template_decl
cleared would be correct.
I don't think we can get away with not calling break_out_target_exprs at all
in a template; if nothing else, we would lose immediate invocation expansion.
However, we could probably skip the bot_manip tree walk, which should avoid
the problem.
Either way we end up returning non-template trees, as we do now, and callers
have to deal with transient CONSTRUCTORs containing such (as we do in
massage_init_elt).
Ah I see, makes sense.
Does convert_default_arg not run into the same problem, e.g. when calling
void g(B = {0});
In practice it seems not, because we don't call convert_default_arg
when processing_template_decl is set (verified with an assert to
that effect). In build_over_call for example we exit early when
processing_template_decl is set, and return a templated CALL_EXPR
that doesn't include default arguments at all. A consequence of
this is that we don't reject ahead of time a call that would use
an ill-formed dependent default argument, e.g.
template<class T>
void g(B = T{0});
template<class>
void f() {
g<void>();
}
since the default argument instantiation would be the responsibility
of convert_default_arg.
Thinking hypothetically here, if we do in the future want to include default
arguments in the templated form of a CALL_EXPR,
We definitely do not want to; the templated form should be as close as
possible to the source.
We might want to perform non-dependent conversions to get any errors
(such as this one) before throwing away the result. Which would be
parallel to what we currently do in calling get_nsdmi, and would want
the same behavior.
[snip]
shall we go with the original approach to clear
processing_template_decl directly from get_nsdmi?
OK, but then we should also checking_assert !processing_template_decl in
b_o_t_e.
Jason
?
Bootstrapped and regtested on x86_64-pc-linux-gnu.
PR c++/108116
gcc/cp/ChangeLog:
* init.cc (get_nsdmi): Clear processing_template_decl before
processing the non-templated initializer.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/nsdmi-template24.C: New test.
---
gcc/cp/init.cc | 8 ++++++-
gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C | 22 +++++++++++++++++++
2 files changed, 29 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C
diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index 73e6547c076..c4345ebdaea 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -561,7 +561,8 @@ perform_target_ctor (tree init)
return init;
}
-/* Return the non-static data initializer for FIELD_DECL MEMBER. */
+/* Return the non-static data initializer for FIELD_DECL MEMBER.
+ The initializer returned is always non-templated. */
static GTY((cache)) decl_tree_cache_map *nsdmi_inst;
@@ -670,6 +671,11 @@ get_nsdmi (tree member, bool in_ctor, tsubst_flags_t
complain)
current_class_ptr = build_address (current_class_ref);
}
+ /* Since INIT is always non-templated clear processing_template_decl
+ before processing it so that we don't interleave templated and
+ non-templated trees. */
+ processing_template_decl_sentinel ptds;
+
/* Strip redundant TARGET_EXPR so we don't need to remap it, and
so the aggregate init code below will see a CONSTRUCTOR. */
bool simple_target = (init && SIMPLE_TARGET_EXPR_P (init));
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C
b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C
new file mode 100644
index 00000000000..202c67d7321
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C
@@ -0,0 +1,22 @@
+// PR c++/108116
+// { dg-do compile { target c++11 } }
+
+#include <initializer_list>
+
+struct A {
+ A(int);
+ ~A();
+};
+
+struct B {
+ B(std::initializer_list<A>);
+};
+
+struct C {
+ B m{0};
+};
+
+template<class>
+void f() {
+ C c = C{};
+};
