c++: get_nsdmi in template context [PR108116]

  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?

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
  

On Wed, 21 Dec 2022, 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?
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu.

Note this is a 12 regression so I suppose there's also the question of
what's safest to backport vs what's the best fix..

> 
> 	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{};
> +};
> -- 
> 2.39.0.95.g7c2ef319c5
> 
>
  

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).

Does convert_default_arg not run into the same problem, e.g. when calling

   void g(B = {0});

?

> 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{};
> +};
  

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'd probably have to
instantiate them with processing_template_decl set so that the result is
templated.  And we'd subsequently want to call break_out_target_exprs on
the result also with processing_template_decl set IIUC, to perform
immediate invocation expansion.  This seems to be a potential use case
for being able to call break_out_target_exprs on templated trees, and so
unconditionally clearing p_t_d from break_out_target_exprs might not be
future proof.

In light of this, shall we go with the original approach to clear
processing_template_decl directly from get_nsdmi?

> 
> ?
> 
> > 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{};
> > +};
> 
>
  

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{};
>>> +};
>>
>>
>
  

On Thu, 22 Dec 2022, Jason Merrill wrote:

> 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.

Ah, sounds good.

> 
> 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.

*nod*

> 
> > [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.

Unfortunately we'd trigger that assert from maybe_constant_value, which
potentially calls b_o_t_e with processing_template_decl set.

> 
> 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{};
> > > > +};
> > > 
> > > 
> > 
> 
>
  

On 12/22/22 16:41, Patrick Palka wrote:
> On Thu, 22 Dec 2022, Jason Merrill wrote:
> 
>> 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.
> 
> Ah, sounds good.
> 
>>
>> 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.
> 
> *nod*
> 
>>
>>> [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.
> 
> Unfortunately we'd trigger that assert from maybe_constant_value, which
> potentially calls b_o_t_e with processing_template_decl set.

maybe_constant_value could also clear processing_template_decl; entries 
in cv_cache are non-templated.

>>>>> 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{};
>>>>> +};
>>>>
>>>>
>>>
>>
>>
>
  

On Thu, 22 Dec 2022, Jason Merrill wrote:

> On 12/22/22 16:41, Patrick Palka wrote:
> > On Thu, 22 Dec 2022, Jason Merrill wrote:
> > 
> > > 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.
> > 
> > Ah, sounds good.
> > 
> > > 
> > > 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.
> > 
> > *nod*
> > 
> > > 
> > > > [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.
> > 
> > Unfortunately we'd trigger that assert from maybe_constant_value, which
> > potentially calls b_o_t_e with processing_template_decl set.
> 
> maybe_constant_value could also clear processing_template_decl; entries in
> cv_cache are non-templated.

Aha!  I'll try that.

> 
> > > > > > 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{};
> > > > > > +};
> > > > > 
> > > > > 
> > > > 
> > > 
> > > 
> > 
> 
>
  

On Thu, 22 Dec 2022, Patrick Palka wrote:

> On Thu, 22 Dec 2022, Jason Merrill wrote:
> 
> > On 12/22/22 16:41, Patrick Palka wrote:
> > > On Thu, 22 Dec 2022, Jason Merrill wrote:
> > > 
> > > > 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.
> > > 
> > > Ah, sounds good.
> > > 
> > > > 
> > > > 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.
> > > 
> > > *nod*
> > > 
> > > > 
> > > > > [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.
> > > 
> > > Unfortunately we'd trigger that assert from maybe_constant_value, which
> > > potentially calls b_o_t_e with processing_template_decl set.
> > 
> > maybe_constant_value could also clear processing_template_decl; entries in
> > cv_cache are non-templated.
> 
> Aha!  I'll try that.

How does this look?  Bootstrapped and regtested on x86_64-pc-linux-gnu.

-- >8 --

Subject: [PATCH] c++: get_nsdmi in template context [PR108116]

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 build a call to A::~A and check 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 was recently
changed by r12-6897-gdec8d0e5fa00ceb2) which expr_noexcept_p doesn't
expect, and we crash.

This patch fixes this by clearing processing_template_decl before
the call to break_out_target_exprs from get_nsdmi.  And since it more
generally seems we shouldn't be seeing (or producing) non-templated
trees from break_out_target_exprs, this patch also adds an assert to
that effect.

	PR c++/108116

gcc/cp/ChangeLog:

	* constexpr.cc (maybe_constant_value): Clear
	processing_template_decl before calling break_out_target_exprs.
	* init.cc (get_nsdmi): Likewise.
	* tree.cc (break_out_target_exprs): Assert processing_template_decl
	is cleared.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/nsdmi-template24.C: New test.
---
 gcc/cp/constexpr.cc                           |  4 ++++
 gcc/cp/init.cc                                |  4 ++++
 gcc/cp/tree.cc                                |  4 ++++
 gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C | 22 +++++++++++++++++++
 4 files changed, 34 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index d99c49bdbe2..414af7a6d4c 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -8507,6 +8507,10 @@ maybe_constant_value (tree t, tree decl /* = NULL_TREE */,
       r = *cached;
       if (r != t)
 	{
+	  /* Clear processing_template_decl for sake of break_out_target_exprs;
+	     entries in the cv_cache are non-templated.  */
+	  processing_template_decl_sentinel ptds;
+
 	  r = break_out_target_exprs (r, /*clear_loc*/true);
 	  protected_set_expr_location (r, EXPR_LOCATION (t));
 	}
diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index 73e6547c076..b49a7ca9169 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -670,6 +670,10 @@ get_nsdmi (tree member, bool in_ctor, tsubst_flags_t complain)
       current_class_ptr = build_address (current_class_ref);
     }
 
+  /* Clear processing_template_decl for sake of break_out_target_exprs;
+     INIT is always non-templated.  */
+  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/cp/tree.cc b/gcc/cp/tree.cc
index 33bde16f128..faf01616f87 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -3342,6 +3342,10 @@ break_out_target_exprs (tree t, bool clear_location /* = false */)
   static int target_remap_count;
   static splay_tree target_remap;
 
+  /* We shouldn't be called on templated trees, nor do we want to
+     produce them.  */
+  gcc_checking_assert (!processing_template_decl);
+
   if (!target_remap_count++)
     target_remap = splay_tree_new (splay_tree_compare_pointers,
 				   /*splay_tree_delete_key_fn=*/NULL,
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{};
+};
  

On 12/23/22 10:48, Patrick Palka wrote:
> On Thu, 22 Dec 2022, Patrick Palka wrote:
> 
>> On Thu, 22 Dec 2022, Jason Merrill wrote:
>>
>>> On 12/22/22 16:41, Patrick Palka wrote:
>>>> On Thu, 22 Dec 2022, Jason Merrill wrote:
>>>>
>>>>> 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.
>>>>
>>>> Ah, sounds good.
>>>>
>>>>>
>>>>> 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.
>>>>
>>>> *nod*
>>>>
>>>>>
>>>>>> [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.
>>>>
>>>> Unfortunately we'd trigger that assert from maybe_constant_value, which
>>>> potentially calls b_o_t_e with processing_template_decl set.
>>>
>>> maybe_constant_value could also clear processing_template_decl; entries in
>>> cv_cache are non-templated.
>>
>> Aha!  I'll try that.
> 
> How does this look?  Bootstrapped and regtested on x86_64-pc-linux-gnu.

OK.

> -- >8 --
> 
> Subject: [PATCH] c++: get_nsdmi in template context [PR108116]
> 
> 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 build a call to A::~A and check 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 was recently
> changed by r12-6897-gdec8d0e5fa00ceb2) which expr_noexcept_p doesn't
> expect, and we crash.
> 
> This patch fixes this by clearing processing_template_decl before
> the call to break_out_target_exprs from get_nsdmi.  And since it more
> generally seems we shouldn't be seeing (or producing) non-templated
> trees from break_out_target_exprs, this patch also adds an assert to
> that effect.
> 
> 	PR c++/108116
> 
> gcc/cp/ChangeLog:
> 
> 	* constexpr.cc (maybe_constant_value): Clear
> 	processing_template_decl before calling break_out_target_exprs.
> 	* init.cc (get_nsdmi): Likewise.
> 	* tree.cc (break_out_target_exprs): Assert processing_template_decl
> 	is cleared.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/nsdmi-template24.C: New test.
> ---
>   gcc/cp/constexpr.cc                           |  4 ++++
>   gcc/cp/init.cc                                |  4 ++++
>   gcc/cp/tree.cc                                |  4 ++++
>   gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C | 22 +++++++++++++++++++
>   4 files changed, 34 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/nsdmi-template24.C
> 
> diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> index d99c49bdbe2..414af7a6d4c 100644
> --- a/gcc/cp/constexpr.cc
> +++ b/gcc/cp/constexpr.cc
> @@ -8507,6 +8507,10 @@ maybe_constant_value (tree t, tree decl /* = NULL_TREE */,
>         r = *cached;
>         if (r != t)
>   	{
> +	  /* Clear processing_template_decl for sake of break_out_target_exprs;
> +	     entries in the cv_cache are non-templated.  */
> +	  processing_template_decl_sentinel ptds;
> +
>   	  r = break_out_target_exprs (r, /*clear_loc*/true);
>   	  protected_set_expr_location (r, EXPR_LOCATION (t));
>   	}
> diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
> index 73e6547c076..b49a7ca9169 100644
> --- a/gcc/cp/init.cc
> +++ b/gcc/cp/init.cc
> @@ -670,6 +670,10 @@ get_nsdmi (tree member, bool in_ctor, tsubst_flags_t complain)
>         current_class_ptr = build_address (current_class_ref);
>       }
>   
> +  /* Clear processing_template_decl for sake of break_out_target_exprs;
> +     INIT is always non-templated.  */
> +  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/cp/tree.cc b/gcc/cp/tree.cc
> index 33bde16f128..faf01616f87 100644
> --- a/gcc/cp/tree.cc
> +++ b/gcc/cp/tree.cc
> @@ -3342,6 +3342,10 @@ break_out_target_exprs (tree t, bool clear_location /* = false */)
>     static int target_remap_count;
>     static splay_tree target_remap;
>   
> +  /* We shouldn't be called on templated trees, nor do we want to
> +     produce them.  */
> +  gcc_checking_assert (!processing_template_decl);
> +
>     if (!target_remap_count++)
>       target_remap = splay_tree_new (splay_tree_compare_pointers,
>   				   /*splay_tree_delete_key_fn=*/NULL,
> 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{};
> +};