[v4] c++: ICE with temporary of class type in DMI [PR100252]
Commit Message
On Sat, May 07, 2022 at 06:02:13PM -0400, Jason Merrill wrote:
> On 5/7/22 15:11, Marek Polacek wrote:
> > On Tue, May 03, 2022 at 04:59:38PM -0400, Jason Merrill wrote:
> > > Does this testcase still work with this patch?
> > >
> > > struct A {
> > > const A* p = this;
> > > };
> > >
> > > struct B {
> > > A a = A{};
> > > };
> > >
> > > constexpr B b;
> > > static_assert (b.a.p == &b.a);
> >
> > Ouch, no. Thanks for catching this, it would have been very unpleasant
> > to hit this problem later...
> >
> > The reason your testcase was rejected is that replacing a PLACEHOLDER
> > in the outermost TARGET_EXPR broke guaranteed copy elision. Now that
> > I've spent another day on this, I still think we have to replace the
> > placeholders created when temporary materialization takes place in an
> > NSDMI, but it must happen in digest_nsdmi_init (as Patrick suggested),
> > where we can see the full initializer. That way I can avoid breaking
> > copy elision.
> >
> > I've added a bunch of new testcases and updated the
> > (already long) description. The yuge comment hopefully also explains
> > how this problem is avoided. Thanks again,
> >
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> >
> > -- >8 --
> > Consider
> >
> > struct A {
> > int x;
> > int y = x;
> > };
> >
> > struct B {
> > int x = 0;
> > int y = A{x}.y; // #1
> > };
> >
> > where for #1 we end up with
> >
> > {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
> >
> > that is, two PLACEHOLDER_EXPRs for different types on the same level in
> > a {}. This crashes because our CONSTRUCTOR_PLACEHOLDER_BOUNDARY mechanism to
> > avoid replacing unrelated PLACEHOLDER_EXPRs cannot deal with it.
> >
> > Here's why we wound up with those PLACEHOLDER_EXPRs: When we're performing
> > cp_parser_late_parsing_nsdmi for "int y = A{x}.y;" we use finish_compound_literal
> > on type=A, compound_literal={((struct B *) this)->x}. When digesting this
> > initializer, we call get_nsdmi which creates a PLACEHOLDER_EXPR for A -- we don't
> > have any object to refer to yet. After digesting, we have
> >
> > {.x=((struct B *) this)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
> >
> > and since we've created a PLACEHOLDER_EXPR inside it, we marked the whole ctor
> > CONSTRUCTOR_PLACEHOLDER_BOUNDARY. f_c_l creates a TARGET_EXPR and returns
> >
> > TARGET_EXPR <D.2384, {.x=((struct B *) this)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}>
> >
> > Then we get to
> >
> > B b = {};
> >
> > and call store_init_value, which digests the {}, which produces
> >
> > {.x=NON_LVALUE_EXPR <0>, .y=(TARGET_EXPR <D.2395, {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}>).y}
> >
> > lookup_placeholder in constexpr won't find an object to replace the
> > PLACEHOLDER_EXPR for B, because ctx->object will be D.2395 of type A, and we
> > cannot search outward from D.2395 to find 'b'.
> >
> > The call to replace_placeholders in store_init_value will not do anything:
> > we've marked the inner { } CONSTRUCTOR_PLACEHOLDER_BOUNDARY, and it's only
> > a sub-expression, so replace_placeholders does nothing, so the <P_E struct B>
> > stays even though now is the perfect time to replace it because we have an
> > object for it: 'b'.
> >
> > Later, in cp_gimplify_init_expr the *expr_p is
> >
> > D.2395 = {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
> >
> > where D.2395 is of type A, but we crash because we hit <P_E struct B>, which
> > has a different type.
> >
> > My idea was to replace <P_E struct A> with D.2384 after creating the
> > TARGET_EXPR because that means we have an object we can refer to.
> > Then clear CONSTRUCTOR_PLACEHOLDER_BOUNDARY because we no longer have
> > a PLACEHOLDER_EXPR in the {}. Then store_init_value will be able to
> > replace <P_E struct B> with 'b', and we should be good to go. We must
> > be careful not to break guaranteed copy elision, so this replacement
> > happens in digest_nsdmi_init where we can see the whole initializer,
> > and avoid replacing any placeholders in the outermost TARGET_EXPR.
> >
> > PR c++/100252
> >
> > gcc/cp/ChangeLog:
> >
> > * typeck2.cc (replace_placeholders_for_class_temp_r): New.
> > (digest_nsdmi_init): Call it.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp1y/nsdmi-aggr14.C: New test.
> > * g++.dg/cpp1y/nsdmi-aggr15.C: New test.
> > * g++.dg/cpp1y/nsdmi-aggr16.C: New test.
> > * g++.dg/cpp1y/nsdmi-aggr17.C: New test.
> > * g++.dg/cpp1y/nsdmi-aggr18.C: New test.
> > ---
> > gcc/cp/typeck2.cc | 54 +++++++++++++++++++++++
> > gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C | 46 +++++++++++++++++++
> > gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C | 29 ++++++++++++
> > gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C | 19 ++++++++
> > gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C | 47 ++++++++++++++++++++
> > gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C | 25 +++++++++++
> > 6 files changed, 220 insertions(+)
> > create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C
> >
> > diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
> > index 63d95c1529a..72d7cfaf1d3 100644
> > --- a/gcc/cp/typeck2.cc
> > +++ b/gcc/cp/typeck2.cc
> > @@ -1371,6 +1371,34 @@ digest_init_flags (tree type, tree init, int flags, tsubst_flags_t complain)
> > return digest_init_r (type, init, 0, flags, complain);
> > }
> > +/* Callback to replace PLACEHOLDER_EXPRs in a TARGET_EXPR (which isn't used
> > + in the context of guaranteed copy elision). */
> > +
> > +static tree
> > +replace_placeholders_for_class_temp_r (tree *tp, int *walk_subtrees, void *data)
> > +{
> > + tree t = *tp;
> > + tree full_expr = *static_cast<tree *>(data);
> > +
> > + /* We're looking for a TARGET_EXPR nested in the whole expression. */
> > + if (TREE_CODE (t) == TARGET_EXPR && t != full_expr)
>
> Just comparing to full_expr doesn't seem enough to catch all the cases where
> a prvalue is used as an initializer rather than for temporary
> materialization; you will also need to handle comma and conditional
> expressions. And probably PAREN_EXPR.
>
> I'm failing to find a term for this in the standard; "potential result" also
> includes objects that the result is an xvalue subobject of (as in #1 below).
> Maybe "potential prvalue result", to exclude the xvalue cases? So,
>
> && !potential_prvalue_result_of (t, full_expr)
>
> ?
Thanks, the previous version indeed did have problems when ?: or , was used.
I've greatly enhanced the tests to detect more cases, and added
potential_prvalue_result_of.
While looking into this, I found PR105550, which turned out to be a big
can of worms. So, XFAIL for now.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
Consider
struct A {
int x;
int y = x;
};
struct B {
int x = 0;
int y = A{x}.y; // #1
};
where for #1 we end up with
{.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
that is, two PLACEHOLDER_EXPRs for different types on the same level in
a {}. This crashes because our CONSTRUCTOR_PLACEHOLDER_BOUNDARY mechanism to
avoid replacing unrelated PLACEHOLDER_EXPRs cannot deal with it.
Here's why we wound up with those PLACEHOLDER_EXPRs: When we're performing
cp_parser_late_parsing_nsdmi for "int y = A{x}.y;" we use finish_compound_literal
on type=A, compound_literal={((struct B *) this)->x}. When digesting this
initializer, we call get_nsdmi which creates a PLACEHOLDER_EXPR for A -- we don't
have any object to refer to yet. After digesting, we have
{.x=((struct B *) this)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
and since we've created a PLACEHOLDER_EXPR inside it, we marked the whole ctor
CONSTRUCTOR_PLACEHOLDER_BOUNDARY. f_c_l creates a TARGET_EXPR and returns
TARGET_EXPR <D.2384, {.x=((struct B *) this)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}>
Then we get to
B b = {};
and call store_init_value, which digests the {}, which produces
{.x=NON_LVALUE_EXPR <0>, .y=(TARGET_EXPR <D.2395, {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}>).y}
lookup_placeholder in constexpr won't find an object to replace the
PLACEHOLDER_EXPR for B, because ctx->object will be D.2395 of type A, and we
cannot search outward from D.2395 to find 'b'.
The call to replace_placeholders in store_init_value will not do anything:
we've marked the inner { } CONSTRUCTOR_PLACEHOLDER_BOUNDARY, and it's only
a sub-expression, so replace_placeholders does nothing, so the <P_E struct B>
stays even though now is the perfect time to replace it because we have an
object for it: 'b'.
Later, in cp_gimplify_init_expr the *expr_p is
D.2395 = {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
where D.2395 is of type A, but we crash because we hit <P_E struct B>, which
has a different type.
My idea was to replace <P_E struct A> with D.2384 after creating the
TARGET_EXPR because that means we have an object we can refer to.
Then clear CONSTRUCTOR_PLACEHOLDER_BOUNDARY because we no longer have
a PLACEHOLDER_EXPR in the {}. Then store_init_value will be able to
replace <P_E struct B> with 'b', and we should be good to go. We must
be careful not to break guaranteed copy elision, so this replacement
happens in digest_nsdmi_init where we can see the whole initializer,
and avoid replacing any placeholders in TARGET_EXPRs used in the context
of initialization/copy elision. This is achieved via the new function
called potential_prvalue_result_of.
While fixing this problem, I found PR105550, thus the FIXMEs in the
tests.
PR c++/100252
gcc/cp/ChangeLog:
* typeck2.cc (potential_prvalue_result_of): New.
(replace_placeholders_for_class_temp_r): New.
(digest_nsdmi_init): Call it.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1y/nsdmi-aggr14.C: New test.
* g++.dg/cpp1y/nsdmi-aggr15.C: New test.
* g++.dg/cpp1y/nsdmi-aggr16.C: New test.
* g++.dg/cpp1y/nsdmi-aggr17.C: New test.
* g++.dg/cpp1y/nsdmi-aggr18.C: New test.
* g++.dg/cpp1y/nsdmi-aggr19.C: New test.
---
gcc/cp/typeck2.cc | 90 ++++++++++++++
gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C | 131 ++++++++++++++++++++
gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C | 80 +++++++++++++
gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C | 58 +++++++++
gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C | 138 ++++++++++++++++++++++
gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C | 56 +++++++++
gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr19.C | 28 +++++
7 files changed, 581 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C
create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C
create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C
create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C
create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C
create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr19.C
base-commit: dd7813f05df50d2ad8e0dc34503f2dff0b521d89
Comments
On 5/13/22 19:41, Marek Polacek wrote:
> On Sat, May 07, 2022 at 06:02:13PM -0400, Jason Merrill wrote:
>> On 5/7/22 15:11, Marek Polacek wrote:
>>> On Tue, May 03, 2022 at 04:59:38PM -0400, Jason Merrill wrote:
>>>> Does this testcase still work with this patch?
>>>>
>>>> struct A {
>>>> const A* p = this;
>>>> };
>>>>
>>>> struct B {
>>>> A a = A{};
>>>> };
>>>>
>>>> constexpr B b;
>>>> static_assert (b.a.p == &b.a);
>>>
>>> Ouch, no. Thanks for catching this, it would have been very unpleasant
>>> to hit this problem later...
>>>
>>> The reason your testcase was rejected is that replacing a PLACEHOLDER
>>> in the outermost TARGET_EXPR broke guaranteed copy elision. Now that
>>> I've spent another day on this, I still think we have to replace the
>>> placeholders created when temporary materialization takes place in an
>>> NSDMI, but it must happen in digest_nsdmi_init (as Patrick suggested),
>>> where we can see the full initializer. That way I can avoid breaking
>>> copy elision.
>>>
>>> I've added a bunch of new testcases and updated the
>>> (already long) description. The yuge comment hopefully also explains
>>> how this problem is avoided. Thanks again,
>>>
>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>
>>> -- >8 --
>>> Consider
>>>
>>> struct A {
>>> int x;
>>> int y = x;
>>> };
>>>
>>> struct B {
>>> int x = 0;
>>> int y = A{x}.y; // #1
>>> };
>>>
>>> where for #1 we end up with
>>>
>>> {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
>>>
>>> that is, two PLACEHOLDER_EXPRs for different types on the same level in
>>> a {}. This crashes because our CONSTRUCTOR_PLACEHOLDER_BOUNDARY mechanism to
>>> avoid replacing unrelated PLACEHOLDER_EXPRs cannot deal with it.
>>>
>>> Here's why we wound up with those PLACEHOLDER_EXPRs: When we're performing
>>> cp_parser_late_parsing_nsdmi for "int y = A{x}.y;" we use finish_compound_literal
>>> on type=A, compound_literal={((struct B *) this)->x}. When digesting this
>>> initializer, we call get_nsdmi which creates a PLACEHOLDER_EXPR for A -- we don't
>>> have any object to refer to yet. After digesting, we have
>>>
>>> {.x=((struct B *) this)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
>>>
>>> and since we've created a PLACEHOLDER_EXPR inside it, we marked the whole ctor
>>> CONSTRUCTOR_PLACEHOLDER_BOUNDARY. f_c_l creates a TARGET_EXPR and returns
>>>
>>> TARGET_EXPR <D.2384, {.x=((struct B *) this)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}>
>>>
>>> Then we get to
>>>
>>> B b = {};
>>>
>>> and call store_init_value, which digests the {}, which produces
>>>
>>> {.x=NON_LVALUE_EXPR <0>, .y=(TARGET_EXPR <D.2395, {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}>).y}
>>>
>>> lookup_placeholder in constexpr won't find an object to replace the
>>> PLACEHOLDER_EXPR for B, because ctx->object will be D.2395 of type A, and we
>>> cannot search outward from D.2395 to find 'b'.
>>>
>>> The call to replace_placeholders in store_init_value will not do anything:
>>> we've marked the inner { } CONSTRUCTOR_PLACEHOLDER_BOUNDARY, and it's only
>>> a sub-expression, so replace_placeholders does nothing, so the <P_E struct B>
>>> stays even though now is the perfect time to replace it because we have an
>>> object for it: 'b'.
>>>
>>> Later, in cp_gimplify_init_expr the *expr_p is
>>>
>>> D.2395 = {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
>>>
>>> where D.2395 is of type A, but we crash because we hit <P_E struct B>, which
>>> has a different type.
>>>
>>> My idea was to replace <P_E struct A> with D.2384 after creating the
>>> TARGET_EXPR because that means we have an object we can refer to.
>>> Then clear CONSTRUCTOR_PLACEHOLDER_BOUNDARY because we no longer have
>>> a PLACEHOLDER_EXPR in the {}. Then store_init_value will be able to
>>> replace <P_E struct B> with 'b', and we should be good to go. We must
>>> be careful not to break guaranteed copy elision, so this replacement
>>> happens in digest_nsdmi_init where we can see the whole initializer,
>>> and avoid replacing any placeholders in the outermost TARGET_EXPR.
>>>
>>> PR c++/100252
>>>
>>> gcc/cp/ChangeLog:
>>>
>>> * typeck2.cc (replace_placeholders_for_class_temp_r): New.
>>> (digest_nsdmi_init): Call it.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> * g++.dg/cpp1y/nsdmi-aggr14.C: New test.
>>> * g++.dg/cpp1y/nsdmi-aggr15.C: New test.
>>> * g++.dg/cpp1y/nsdmi-aggr16.C: New test.
>>> * g++.dg/cpp1y/nsdmi-aggr17.C: New test.
>>> * g++.dg/cpp1y/nsdmi-aggr18.C: New test.
>>> ---
>>> gcc/cp/typeck2.cc | 54 +++++++++++++++++++++++
>>> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C | 46 +++++++++++++++++++
>>> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C | 29 ++++++++++++
>>> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C | 19 ++++++++
>>> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C | 47 ++++++++++++++++++++
>>> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C | 25 +++++++++++
>>> 6 files changed, 220 insertions(+)
>>> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C
>>> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C
>>> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C
>>> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C
>>> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C
>>>
>>> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
>>> index 63d95c1529a..72d7cfaf1d3 100644
>>> --- a/gcc/cp/typeck2.cc
>>> +++ b/gcc/cp/typeck2.cc
>>> @@ -1371,6 +1371,34 @@ digest_init_flags (tree type, tree init, int flags, tsubst_flags_t complain)
>>> return digest_init_r (type, init, 0, flags, complain);
>>> }
>>> +/* Callback to replace PLACEHOLDER_EXPRs in a TARGET_EXPR (which isn't used
>>> + in the context of guaranteed copy elision). */
>>> +
>>> +static tree
>>> +replace_placeholders_for_class_temp_r (tree *tp, int *walk_subtrees, void *data)
>>> +{
>>> + tree t = *tp;
>>> + tree full_expr = *static_cast<tree *>(data);
>>> +
>>> + /* We're looking for a TARGET_EXPR nested in the whole expression. */
>>> + if (TREE_CODE (t) == TARGET_EXPR && t != full_expr)
>>
>> Just comparing to full_expr doesn't seem enough to catch all the cases where
>> a prvalue is used as an initializer rather than for temporary
>> materialization; you will also need to handle comma and conditional
>> expressions. And probably PAREN_EXPR.
>>
>> I'm failing to find a term for this in the standard; "potential result" also
>> includes objects that the result is an xvalue subobject of (as in #1 below).
>> Maybe "potential prvalue result", to exclude the xvalue cases? So,
>>
>> && !potential_prvalue_result_of (t, full_expr)
>>
>> ?
>
> Thanks, the previous version indeed did have problems when ?: or , was used.
> I've greatly enhanced the tests to detect more cases, and added
> potential_prvalue_result_of.
>
> While looking into this, I found PR105550, which turned out to be a big
> can of worms. So, XFAIL for now.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
> -- >8 --
> Consider
>
> struct A {
> int x;
> int y = x;
> };
>
> struct B {
> int x = 0;
> int y = A{x}.y; // #1
> };
>
> where for #1 we end up with
>
> {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
>
> that is, two PLACEHOLDER_EXPRs for different types on the same level in
> a {}. This crashes because our CONSTRUCTOR_PLACEHOLDER_BOUNDARY mechanism to
> avoid replacing unrelated PLACEHOLDER_EXPRs cannot deal with it.
>
> Here's why we wound up with those PLACEHOLDER_EXPRs: When we're performing
> cp_parser_late_parsing_nsdmi for "int y = A{x}.y;" we use finish_compound_literal
> on type=A, compound_literal={((struct B *) this)->x}. When digesting this
> initializer, we call get_nsdmi which creates a PLACEHOLDER_EXPR for A -- we don't
> have any object to refer to yet. After digesting, we have
>
> {.x=((struct B *) this)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
>
> and since we've created a PLACEHOLDER_EXPR inside it, we marked the whole ctor
> CONSTRUCTOR_PLACEHOLDER_BOUNDARY. f_c_l creates a TARGET_EXPR and returns
>
> TARGET_EXPR <D.2384, {.x=((struct B *) this)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}>
>
> Then we get to
>
> B b = {};
>
> and call store_init_value, which digests the {}, which produces
>
> {.x=NON_LVALUE_EXPR <0>, .y=(TARGET_EXPR <D.2395, {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}>).y}
>
> lookup_placeholder in constexpr won't find an object to replace the
> PLACEHOLDER_EXPR for B, because ctx->object will be D.2395 of type A, and we
> cannot search outward from D.2395 to find 'b'.
>
> The call to replace_placeholders in store_init_value will not do anything:
> we've marked the inner { } CONSTRUCTOR_PLACEHOLDER_BOUNDARY, and it's only
> a sub-expression, so replace_placeholders does nothing, so the <P_E struct B>
> stays even though now is the perfect time to replace it because we have an
> object for it: 'b'.
>
> Later, in cp_gimplify_init_expr the *expr_p is
>
> D.2395 = {.x=(&<PLACEHOLDER_EXPR struct B>)->x, .y=(&<PLACEHOLDER_EXPR struct A>)->x}
>
> where D.2395 is of type A, but we crash because we hit <P_E struct B>, which
> has a different type.
>
> My idea was to replace <P_E struct A> with D.2384 after creating the
> TARGET_EXPR because that means we have an object we can refer to.
> Then clear CONSTRUCTOR_PLACEHOLDER_BOUNDARY because we no longer have
> a PLACEHOLDER_EXPR in the {}. Then store_init_value will be able to
> replace <P_E struct B> with 'b', and we should be good to go. We must
> be careful not to break guaranteed copy elision, so this replacement
> happens in digest_nsdmi_init where we can see the whole initializer,
> and avoid replacing any placeholders in TARGET_EXPRs used in the context
> of initialization/copy elision. This is achieved via the new function
> called potential_prvalue_result_of.
>
> While fixing this problem, I found PR105550, thus the FIXMEs in the
> tests.
>
> PR c++/100252
>
> gcc/cp/ChangeLog:
>
> * typeck2.cc (potential_prvalue_result_of): New.
> (replace_placeholders_for_class_temp_r): New.
> (digest_nsdmi_init): Call it.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp1y/nsdmi-aggr14.C: New test.
> * g++.dg/cpp1y/nsdmi-aggr15.C: New test.
> * g++.dg/cpp1y/nsdmi-aggr16.C: New test.
> * g++.dg/cpp1y/nsdmi-aggr17.C: New test.
> * g++.dg/cpp1y/nsdmi-aggr18.C: New test.
> * g++.dg/cpp1y/nsdmi-aggr19.C: New test.
> ---
> gcc/cp/typeck2.cc | 90 ++++++++++++++
> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C | 131 ++++++++++++++++++++
> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C | 80 +++++++++++++
> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C | 58 +++++++++
> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C | 138 ++++++++++++++++++++++
> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C | 56 +++++++++
> gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr19.C | 28 +++++
> 7 files changed, 581 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C
> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C
> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C
> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C
> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C
> create mode 100644 gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr19.C
>
> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
> index 1d92310edd0..f60e1df4c27 100644
> --- a/gcc/cp/typeck2.cc
> +++ b/gcc/cp/typeck2.cc
> @@ -1371,6 +1371,70 @@ digest_init_flags (tree type, tree init, int flags, tsubst_flags_t complain)
> return digest_init_r (type, init, 0, flags, complain);
> }
>
> +/* Return true if a prvalue is used as an initializer rather than for
> + temporary materialization. For instance:
I might say "if SUBOB initializes the same object as FULL_EXPR"; the
full-expression could still end up initializing a temporary.
> + A a = A{}; // initializer
> + A a = (A{}); // initializer
> + A a = (1, A{}); // initializer
> + A a = true ? A{} : A{}; // initializer
> + auto x = A{}.x; // temporary materialization
> + auto x = foo(A{}); // temporary materialization
> +
> + FULL_EXPR is the whole expression, SUBOB is its TARGET_EXPR subobject. */
> +
> +static bool
> +potential_prvalue_result_of (tree subob, tree full_expr)
> +{
> + if (subob == full_expr)
> + return true;
> + else if (TREE_CODE (full_expr) == TARGET_EXPR)
> + {
> + tree init = TARGET_EXPR_INITIAL (full_expr);
> + if (TREE_CODE (init) == COND_EXPR)
> + return (potential_prvalue_result_of (subob, TREE_OPERAND (init, 1))
> + || potential_prvalue_result_of (subob, TREE_OPERAND (init, 2)));
> + else if (TREE_CODE (init) == COMPOUND_EXPR)
> + return (potential_prvalue_result_of (subob, TREE_OPERAND (init, 0))
We shouldn't recurse into the LHS of the comma, only the RHS.
> + || potential_prvalue_result_of (subob, TREE_OPERAND (init, 1)));
> + /* ??? I don't know if this can be hit. If so, look inside the ( )
> + instead of the assert. */
> + else if (TREE_CODE (init) == PAREN_EXPR)
> + gcc_checking_assert (false);
It seems trivial enough to recurse after the assert, in case it does
happen in the wild.
> + }
> + return false;
> +}
> +
> +/* Callback to replace PLACEHOLDER_EXPRs in a TARGET_EXPR (which isn't used
> + in the context of guaranteed copy elision). */
> +
> +static tree
> +replace_placeholders_for_class_temp_r (tree *tp, int *, void *data)
> +{
> + tree t = *tp;
> + tree full_expr = *static_cast<tree *>(data);
> +
> + /* We're looking for a TARGET_EXPR nested in the whole expression. */
> + if (TREE_CODE (t) == TARGET_EXPR
> + && !potential_prvalue_result_of (t, full_expr))
> + {
> + tree init = TARGET_EXPR_INITIAL (t);
> + while (TREE_CODE (init) == COMPOUND_EXPR)
> + init = TREE_OPERAND (init, 1);
> + if (TREE_CODE (init) == CONSTRUCTOR
> + && CONSTRUCTOR_PLACEHOLDER_BOUNDARY (init))
> + {
> + tree obj = TARGET_EXPR_SLOT (t);
> + replace_placeholders (init, obj);
> + /* We should have dealt with all PLACEHOLDER_EXPRs. */
> + CONSTRUCTOR_PLACEHOLDER_BOUNDARY (init) = false;
> + gcc_checking_assert (!find_placeholders (init));
> + }
> + }
> +
> + return NULL_TREE;
> +}
> +
> /* Process the initializer INIT for an NSDMI DECL (a FIELD_DECL). */
> tree
> digest_nsdmi_init (tree decl, tree init, tsubst_flags_t complain)
> @@ -1390,6 +1454,32 @@ digest_nsdmi_init (tree decl, tree init, tsubst_flags_t complain)
> && CP_AGGREGATE_TYPE_P (type))
> init = reshape_init (type, init, complain);
> init = digest_init_flags (type, init, flags, complain);
> +
> + /* We may have temporary materialization in a NSDMI, if the initializer
> + has something like A{} in it. Digesting the {} could have introduced
> + a PLACEHOLDER_EXPR referring to A. Now that we've got a TARGET_EXPR,
> + we have an object we can refer to. The reason we bother doing this
> + here is for code like
> +
> + struct A {
> + int x;
> + int y = x;
> + };
> +
> + struct B {
> + int x = 0;
> + int y = A{x}.y; // #1
> + };
> +
> + where in #1 we don't want to end up with two PLACEHOLDER_EXPRs for
> + different types on the same level in a {} when lookup_placeholder
> + wouldn't find a named object for the PLACEHOLDER_EXPR for A. Note,
> + temporary materialization does not occur when initializing an object
> + from a prvalue of the same type, therefore we must not replace the
> + placeholder with a temporary object so that it can be elided. */
> + cp_walk_tree (&init, replace_placeholders_for_class_temp_r, &init,
> + nullptr);
> +
> return init;
> }
>
> diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C
> new file mode 100644
> index 00000000000..28b908a0a1a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr14.C
> @@ -0,0 +1,131 @@
> +// PR c++/100252
> +// { dg-do run { target c++14 } }
> +
> +#define SA(X) static_assert ((X),#X)
> +
> +struct A {
> + int x;
> + int y = x;
> +};
> +
> +struct B {
> + int x = 0;
> + int y = A{x}.y;
> +};
> +
> +constexpr B csb1 = { };
> +SA(csb1.x == 0 && csb1.y == csb1.x);
> +constexpr B csb2 = { 1 };
> +SA(csb2.x == 1 && csb2.y == csb2.x);
> +constexpr B csb3 = { 1, 2 };
> +SA(csb3.x == 1 && csb3.y == 2);
> +
> +B sb1 = { };
> +B sb2 = { 1 };
> +B sb3 = { 1, 2};
> +
> +struct C {
> + int x = 0;
> + int y = (true, A{x}.y) + (A{x}.y, 0);
> +};
> +
> +constexpr C csc1 = { };
> +SA(csc1.x == 0 && csc1.y == csc1.x);
> +constexpr C csc2 = { 1 };
> +SA(csc2.x == 1 && csc2.y == csc2.x);
> +constexpr C csc3 = { 1, 2 };
> +SA(csc3.x == 1 && csc3.y == 2);
> +
> +C sc1 = { };
> +C sc2 = { 1 };
> +C sc3 = { 1, 2};
> +
> +struct D {
> + int x = 0;
> + int y = (A{x}.y);
> +};
> +
> +constexpr D csd1 = { };
> +SA(csd1.x == 0 && csd1.y == csd1.x);
> +constexpr D csd2 = { 1 };
> +SA(csd2.x == 1 && csd2.y == csd2.x);
> +constexpr D csd3 = { 1, 2 };
> +SA(csd3.x == 1 && csd3.y == 2);
> +
> +D sd1 = { };
> +D sd2 = { 1 };
> +D sd3 = { 1, 2};
> +
> +struct E {
> + int x = 0;
> + int y = x ? A{x}.y : A{x}.y;
> +};
> +
> +constexpr E cse1 = { };
> +SA(cse1.x == 0 && cse1.y == cse1.x);
> +constexpr E cse2 = { 1 };
> +SA(cse2.x == 1 && cse2.y == cse2.x);
> +constexpr E cse3 = { 1, 2 };
> +SA(cse3.x == 1 && cse3.y == 2);
> +
> +E se1 = { };
> +E se2 = { 1 };
> +E se3 = { 1, 2};
> +
> +int
> +main ()
> +{
> + if (sb1.x != 0 || sb1.x != sb1.y)
> + __builtin_abort();
> + if (sb2.x != 1 || sb2.x != sb2.y)
> + __builtin_abort();
> + if (sb3.x != 1 || sb3.y != 2)
> + __builtin_abort();
> +
> + if (sc1.x != 0 || sc1.x != sc1.y)
> + __builtin_abort();
> + if (sc2.x != 1 || sc2.x != sc2.y)
> + __builtin_abort();
> + if (sc3.x != 1 || sc3.y != 2)
> + __builtin_abort();
> +
> + B b1 = { };
> + B b2 = { 1 };
> + B b3 = { 1, 2};
> + if (b1.x != 0 || b1.x != b1.y)
> + __builtin_abort();
> + if (b2.x != 1 || b2.x != b2.y)
> + __builtin_abort();
> + if (b3.x != 1 || b3.y != 2)
> + __builtin_abort();
> +
> + C c1 = { };
> + C c2 = { 1 };
> + C c3 = { 1, 2};
> + if (c1.x != 0 || c1.x != c1.y)
> + __builtin_abort();
> + if (c2.x != 1 || c2.x != c2.y)
> + __builtin_abort();
> + if (c3.x != 1 || c3.y != 2)
> + __builtin_abort();
> +
> + D d1 = { };
> + D d2 = { 1 };
> + D d3 = { 1, 2};
> + if (d1.x != 0 || d1.x != d1.y)
> + __builtin_abort();
> + if (d2.x != 1 || d2.x != d2.y)
> + __builtin_abort();
> + if (d3.x != 1 || d3.y != 2)
> + __builtin_abort();
> +
> + E e1 = { };
> + E e2 = { 1 };
> + E e3 = { 1, 2};
> + if (e1.x != 0 || e1.x != e1.y)
> + __builtin_abort();
> + if (e2.x != 1 || e2.x != e2.y)
> + __builtin_abort();
> + if (e3.x != 1 || e3.y != 2)
> + __builtin_abort();
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C
> new file mode 100644
> index 00000000000..d091d693042
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr15.C
> @@ -0,0 +1,80 @@
> +// PR c++/100252
> +// { dg-do run { target c++14 } }
> +
> +struct A {
> + int x;
> + int y = x;
> +};
> +
> +struct B {
> + int x = 0;
> + int y = A{x}.y;
> +};
> +
> +static void
> +test_b (B b1 = B{}, B b2 = B{1}, B b3 = B{1, 2})
> +{
> + if (b1.x != 0 || b1.y != b1.x)
> + __builtin_abort();
> + if (b2.x != 1 || b2.y != b2.x)
> + __builtin_abort();
> + if (b3.x != 1 || b3.y != 2)
> + __builtin_abort();
> +}
> +
> +struct C {
> + int x = 0;
> + int y = (true, A{x}.y) + (A{x}.y, 0);
> +};
> +
> +static void
> +test_c (C c1 = C{}, C c2 = C{1}, C c3 = C{1, 2})
> +{
> + if (c1.x != 0 || c1.y != c1.x)
> + __builtin_abort();
> + if (c2.x != 1 || c2.y != c2.x)
> + __builtin_abort();
> + if (c3.x != 1 || c3.y != 2)
> + __builtin_abort();
> +}
> +
> +struct D {
> + int x = 0;
> + int y = (A{x}.y);
> +};
> +
> +static void
> +test_d (D d1 = D{}, D d2 = D{1}, D d3 = D{1, 2})
> +{
> + if (d1.x != 0 || d1.y != d1.x)
> + __builtin_abort();
> + if (d2.x != 1 || d2.y != d2.x)
> + __builtin_abort();
> + if (d3.x != 1 || d3.y != 2)
> + __builtin_abort();
> +}
> +
> +struct E {
> + int x = 0;
> + int y = x ? A{x}.y : A{x}.y;
> +};
> +
> +static void
> +test_e (E e1 = E{}, E e2 = E{1}, E e3 = E{1, 2})
> +{
> + if (e1.x != 0 || e1.y != e1.x)
> + __builtin_abort();
> + if (e2.x != 1 || e2.y != e2.x)
> + __builtin_abort();
> + if (e3.x != 1 || e3.y != 2)
> + __builtin_abort();
> +}
> +
> +int
> +main ()
> +{
> + test_b ();
> + test_c ();
> + test_d ();
> + test_e ();
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C
> new file mode 100644
> index 00000000000..dc6492c1b0b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr16.C
> @@ -0,0 +1,58 @@
> +// PR c++/100252
> +// { dg-do compile { target c++14 } }
> +
> +#define SA(X) static_assert ((X),#X)
> +
> +struct A {
> + const A* p = this;
> +};
> +
> +struct B {
> + A a = A{};
> +};
> +
> +constexpr B b;
> +SA(b.a.p == &b.a);
> +B b1 = { };
> +
> +struct C {
> + A a = (true, A{});
> +};
> +
> +constexpr C c;
> +SA(c.a.p == &c.a);
> +C c1 = { };
> +
> +struct D {
> + A a = (A{});
> +};
> +
> +constexpr D d;
> +SA(d.a.p == &d.a);
> +D d1 = { };
> +
> +static constexpr A global_a;
> +
> +struct E {
> + A a = true ? A{} : A{};
> + A b = true ? global_a : (false ? A{} : A{});
> + A c = true ? (false ? A{} : A{}) : global_a;
> + A d = true ? (false ? A{} : A{}) : (false ? A{} : A{});
> +};
> +
> +// FIXME: When fixing this, also fix nsdmi-aggr17.C.
> +constexpr E e; // { dg-bogus "" "PR105550" { xfail *-*-* } }
> +SA (e.a.p == &e.a); // { dg-bogus "" "PR105550" { xfail *-*-* } }
> +
> +E e1 = { };
> +
> +struct F {
> + bool b = (A{}, true);
> +};
> +
> +constexpr F f;
> +
> +void
> +g (B b2 = B{}, C c2 = C{}, D d2 = D{}, E e2 = E{})
> +{
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C
> new file mode 100644
> index 00000000000..fc27a2cdac7
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr17.C
> @@ -0,0 +1,138 @@
> +// PR c++/100252
> +// { dg-do run { target c++14 } }
> +
> +#define SA(X) static_assert ((X),#X)
> +
> +struct A {
> + int x;
> + int y = x;
> + const A* p = this;
> +};
> +
> +struct B {
> + int x = 42;
> + A a = A{x};
> +};
> +
> +constexpr B b;
> +SA(b.a.p == &b.a);
> +SA(b.x == 42);
> +B b2 = { };
> +B b3 = { 42 };
> +
> +struct C {
> + int x = 42;
> + B b = B{x};
> +};
> +
> +constexpr C c;
> +C c2;
> +C c3;
> +
> +struct D {
> + int x = 42;
> + A a = (true, A{x});
> +};
> +
> +constexpr D d;
> +SA(d.a.p == &d.a);
> +SA(d.x == 42);
> +D d2 = { };
> +D d3 = { 42 };
> +
> +struct E {
> + int x = 42;
> + A a = (A{x});
> +};
> +
> +constexpr E e;
> +SA(e.a.p == &e.a);
> +SA(e.x == 42);
> +E e2 = { };
> +E e3 = { 42 };
> +
> +struct F {
> + int x = 42;
> + A a = true ? A{x} : A{x};
> +};
> +
> +// FIXME: Doesn't work due to PR105550.
> +//constexpr F f;
> +//SA (f.a.p == &f.a);
> +SA (e.x == 42);
> +F f2 = { };
> +F f3 = { 42 };
> +
> +static void
> +test_b (B b4 = B{}, B b5 = B{ 42 })
> +{
> + if (b2.x != 42 || b2.a.x != 42 || b2.a.y != b2.a.x)
> + __builtin_abort ();
> + if (b3.x != 42 || b3.a.x != 42 || b3.a.y != b3.a.x)
> + __builtin_abort ();
> + if (b4.x != 42 || b4.a.x != 42 || b4.a.y != b4.a.x)
> + __builtin_abort ();
> + if (b5.x != 42 || b5.a.x != 42 || b5.a.y != b5.a.x)
> + __builtin_abort ();
> +}
> +
> +static void
> +test_c (C c4 = C{}, C c5 = C{ 42 })
> +{
> + if (c2.b.x != 42 || c2.b.a.x != 42 || c2.b.a.y != c2.b.a.x)
> + __builtin_abort ();
> + if (c3.b.x != 42 || c3.b.a.x != 42 || c3.b.a.y != c3.b.a.x)
> + __builtin_abort ();
> + if (c4.b.x != 42 || c4.b.a.x != 42 || c4.b.a.y != c4.b.a.x)
> + __builtin_abort ();
> + if (c5.b.x != 42 || c5.b.a.x != 42 || c5.b.a.y != c5.b.a.x)
> + __builtin_abort ();
> +}
> +
> +static void
> +test_d (D d4 = D{}, D d5 = D{ 42 })
> +{
> + if (d2.x != 42 || d2.a.x != 42 || d2.a.y != d2.a.x)
> + __builtin_abort ();
> + if (d3.x != 42 || d3.a.x != 42 || d3.a.y != d3.a.x)
> + __builtin_abort ();
> + if (d4.x != 42 || d4.a.x != 42 || d4.a.y != d4.a.x)
> + __builtin_abort ();
> + if (d5.x != 42 || d5.a.x != 42 || d5.a.y != d5.a.x)
> + __builtin_abort ();
> +}
> +
> +static void
> +test_e (E e4 = E{}, E e5 = E{ 42 })
> +{
> + if (e2.x != 42 || e2.a.x != 42 || e2.a.y != e2.a.x)
> + __builtin_abort ();
> + if (e3.x != 42 || e3.a.x != 42 || e3.a.y != e3.a.x)
> + __builtin_abort ();
> + if (e4.x != 42 || e4.a.x != 42 || e4.a.y != e4.a.x)
> + __builtin_abort ();
> + if (e5.x != 42 || e5.a.x != 42 || e5.a.y != e5.a.x)
> + __builtin_abort ();
> +}
> +
> +static void
> +test_f (F f4 = F{}, F f5 = F{ 42 })
> +{
> + if (f2.x != 42 || f2.a.x != 42 || f2.a.y != f2.a.x)
> + __builtin_abort ();
> + if (f3.x != 42 || f3.a.x != 42 || f3.a.y != f3.a.x)
> + __builtin_abort ();
> + if (f4.x != 42 || f4.a.x != 42 || f4.a.y != f4.a.x)
> + __builtin_abort ();
> + if (f5.x != 42 || f5.a.x != 42 || f5.a.y != f5.a.x)
> + __builtin_abort ();
> +}
> +int
> +main ()
> +{
> + test_b ();
> + test_c ();
> + test_d ();
> + test_e ();
> + test_f ();
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C
> new file mode 100644
> index 00000000000..567b8ee96d9
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr18.C
> @@ -0,0 +1,56 @@
> +// PR c++/100252
> +// { dg-do compile { target c++14 } }
> +
> +struct B { };
> +
> +struct A {
> + int x;
> + int y = x;
> + constexpr operator B() { return B{}; }
> +};
> +
> +struct C {
> + int x = 42;
> + B b = A{x};
> +};
> +
> +C c1 = {};
> +C c2 = { 42 };
> +constexpr C c3 = {};
> +constexpr C c4 = { 42 };
> +
> +struct D {
> + int x = 42;
> + B b = (true, A{x});
> +};
> +
> +D d1 = {};
> +D d2 = { 42 };
> +constexpr D d3 = {};
> +constexpr D d4 = { 42 };
> +
> +struct E {
> + int x = 42;
> + B b = (A{x});
> +};
> +
> +E e1 = {};
> +E e2 = { 42 };
> +constexpr E e3 = {};
> +constexpr E e4 = { 42 };
> +
> +struct F {
> + int x = 42;
> + B b = (A{x});
> +};
> +
> +F f1 = {};
> +F f2 = { 42 };
> +constexpr F f3 = {};
> +constexpr F f4 = { 42 };
> +
> +void
> +g (C c5 = C{}, C c6 = C{ 42 }, D d5 = D{}, D d6 = D{ 42 },
> + E e5 = E{}, E e6 = E{ 42 }, F f5 = F{}, F f6 = F{ 42 })
> +{
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr19.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr19.C
> new file mode 100644
> index 00000000000..f4892e3379b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr19.C
> @@ -0,0 +1,28 @@
> +// PR c++/100252
> +// { dg-do compile { target c++14 } }
> +
> +#define SA(X) static_assert ((X),#X)
> +
> +struct A {
> + const A* p = this;
> +};
> +
> +struct B {
> + A a = (A{}, A{});
> +};
> +
> +constexpr B b;
> +SA(b.a.p == &b.a);
> +
> +struct C {
> + int x;
> + int y = x;
> +};
> +
> +struct D {
> + int x = 0;
> + int y = (C{x}.y, C{x}.y);
> +};
> +
> +constexpr D d = { };
> +D d2 = {};
>
> base-commit: dd7813f05df50d2ad8e0dc34503f2dff0b521d89
@@ -1371,6 +1371,70 @@ digest_init_flags (tree type, tree init, int flags, tsubst_flags_t complain)
return digest_init_r (type, init, 0, flags, complain);
}
+/* Return true if a prvalue is used as an initializer rather than for
+ temporary materialization. For instance:
+
+ A a = A{}; // initializer
+ A a = (A{}); // initializer
+ A a = (1, A{}); // initializer
+ A a = true ? A{} : A{}; // initializer
+ auto x = A{}.x; // temporary materialization
+ auto x = foo(A{}); // temporary materialization
+
+ FULL_EXPR is the whole expression, SUBOB is its TARGET_EXPR subobject. */
+
+static bool
+potential_prvalue_result_of (tree subob, tree full_expr)
+{
+ if (subob == full_expr)
+ return true;
+ else if (TREE_CODE (full_expr) == TARGET_EXPR)
+ {
+ tree init = TARGET_EXPR_INITIAL (full_expr);
+ if (TREE_CODE (init) == COND_EXPR)
+ return (potential_prvalue_result_of (subob, TREE_OPERAND (init, 1))
+ || potential_prvalue_result_of (subob, TREE_OPERAND (init, 2)));
+ else if (TREE_CODE (init) == COMPOUND_EXPR)
+ return (potential_prvalue_result_of (subob, TREE_OPERAND (init, 0))
+ || potential_prvalue_result_of (subob, TREE_OPERAND (init, 1)));
+ /* ??? I don't know if this can be hit. If so, look inside the ( )
+ instead of the assert. */
+ else if (TREE_CODE (init) == PAREN_EXPR)
+ gcc_checking_assert (false);
+ }
+ return false;
+}
+
+/* Callback to replace PLACEHOLDER_EXPRs in a TARGET_EXPR (which isn't used
+ in the context of guaranteed copy elision). */
+
+static tree
+replace_placeholders_for_class_temp_r (tree *tp, int *, void *data)
+{
+ tree t = *tp;
+ tree full_expr = *static_cast<tree *>(data);
+
+ /* We're looking for a TARGET_EXPR nested in the whole expression. */
+ if (TREE_CODE (t) == TARGET_EXPR
+ && !potential_prvalue_result_of (t, full_expr))
+ {
+ tree init = TARGET_EXPR_INITIAL (t);
+ while (TREE_CODE (init) == COMPOUND_EXPR)
+ init = TREE_OPERAND (init, 1);
+ if (TREE_CODE (init) == CONSTRUCTOR
+ && CONSTRUCTOR_PLACEHOLDER_BOUNDARY (init))
+ {
+ tree obj = TARGET_EXPR_SLOT (t);
+ replace_placeholders (init, obj);
+ /* We should have dealt with all PLACEHOLDER_EXPRs. */
+ CONSTRUCTOR_PLACEHOLDER_BOUNDARY (init) = false;
+ gcc_checking_assert (!find_placeholders (init));
+ }
+ }
+
+ return NULL_TREE;
+}
+
/* Process the initializer INIT for an NSDMI DECL (a FIELD_DECL). */
tree
digest_nsdmi_init (tree decl, tree init, tsubst_flags_t complain)
@@ -1390,6 +1454,32 @@ digest_nsdmi_init (tree decl, tree init, tsubst_flags_t complain)
&& CP_AGGREGATE_TYPE_P (type))
init = reshape_init (type, init, complain);
init = digest_init_flags (type, init, flags, complain);
+
+ /* We may have temporary materialization in a NSDMI, if the initializer
+ has something like A{} in it. Digesting the {} could have introduced
+ a PLACEHOLDER_EXPR referring to A. Now that we've got a TARGET_EXPR,
+ we have an object we can refer to. The reason we bother doing this
+ here is for code like
+
+ struct A {
+ int x;
+ int y = x;
+ };
+
+ struct B {
+ int x = 0;
+ int y = A{x}.y; // #1
+ };
+
+ where in #1 we don't want to end up with two PLACEHOLDER_EXPRs for
+ different types on the same level in a {} when lookup_placeholder
+ wouldn't find a named object for the PLACEHOLDER_EXPR for A. Note,
+ temporary materialization does not occur when initializing an object
+ from a prvalue of the same type, therefore we must not replace the
+ placeholder with a temporary object so that it can be elided. */
+ cp_walk_tree (&init, replace_placeholders_for_class_temp_r, &init,
+ nullptr);
+
return init;
}
new file mode 100644
@@ -0,0 +1,131 @@
+// PR c++/100252
+// { dg-do run { target c++14 } }
+
+#define SA(X) static_assert ((X),#X)
+
+struct A {
+ int x;
+ int y = x;
+};
+
+struct B {
+ int x = 0;
+ int y = A{x}.y;
+};
+
+constexpr B csb1 = { };
+SA(csb1.x == 0 && csb1.y == csb1.x);
+constexpr B csb2 = { 1 };
+SA(csb2.x == 1 && csb2.y == csb2.x);
+constexpr B csb3 = { 1, 2 };
+SA(csb3.x == 1 && csb3.y == 2);
+
+B sb1 = { };
+B sb2 = { 1 };
+B sb3 = { 1, 2};
+
+struct C {
+ int x = 0;
+ int y = (true, A{x}.y) + (A{x}.y, 0);
+};
+
+constexpr C csc1 = { };
+SA(csc1.x == 0 && csc1.y == csc1.x);
+constexpr C csc2 = { 1 };
+SA(csc2.x == 1 && csc2.y == csc2.x);
+constexpr C csc3 = { 1, 2 };
+SA(csc3.x == 1 && csc3.y == 2);
+
+C sc1 = { };
+C sc2 = { 1 };
+C sc3 = { 1, 2};
+
+struct D {
+ int x = 0;
+ int y = (A{x}.y);
+};
+
+constexpr D csd1 = { };
+SA(csd1.x == 0 && csd1.y == csd1.x);
+constexpr D csd2 = { 1 };
+SA(csd2.x == 1 && csd2.y == csd2.x);
+constexpr D csd3 = { 1, 2 };
+SA(csd3.x == 1 && csd3.y == 2);
+
+D sd1 = { };
+D sd2 = { 1 };
+D sd3 = { 1, 2};
+
+struct E {
+ int x = 0;
+ int y = x ? A{x}.y : A{x}.y;
+};
+
+constexpr E cse1 = { };
+SA(cse1.x == 0 && cse1.y == cse1.x);
+constexpr E cse2 = { 1 };
+SA(cse2.x == 1 && cse2.y == cse2.x);
+constexpr E cse3 = { 1, 2 };
+SA(cse3.x == 1 && cse3.y == 2);
+
+E se1 = { };
+E se2 = { 1 };
+E se3 = { 1, 2};
+
+int
+main ()
+{
+ if (sb1.x != 0 || sb1.x != sb1.y)
+ __builtin_abort();
+ if (sb2.x != 1 || sb2.x != sb2.y)
+ __builtin_abort();
+ if (sb3.x != 1 || sb3.y != 2)
+ __builtin_abort();
+
+ if (sc1.x != 0 || sc1.x != sc1.y)
+ __builtin_abort();
+ if (sc2.x != 1 || sc2.x != sc2.y)
+ __builtin_abort();
+ if (sc3.x != 1 || sc3.y != 2)
+ __builtin_abort();
+
+ B b1 = { };
+ B b2 = { 1 };
+ B b3 = { 1, 2};
+ if (b1.x != 0 || b1.x != b1.y)
+ __builtin_abort();
+ if (b2.x != 1 || b2.x != b2.y)
+ __builtin_abort();
+ if (b3.x != 1 || b3.y != 2)
+ __builtin_abort();
+
+ C c1 = { };
+ C c2 = { 1 };
+ C c3 = { 1, 2};
+ if (c1.x != 0 || c1.x != c1.y)
+ __builtin_abort();
+ if (c2.x != 1 || c2.x != c2.y)
+ __builtin_abort();
+ if (c3.x != 1 || c3.y != 2)
+ __builtin_abort();
+
+ D d1 = { };
+ D d2 = { 1 };
+ D d3 = { 1, 2};
+ if (d1.x != 0 || d1.x != d1.y)
+ __builtin_abort();
+ if (d2.x != 1 || d2.x != d2.y)
+ __builtin_abort();
+ if (d3.x != 1 || d3.y != 2)
+ __builtin_abort();
+
+ E e1 = { };
+ E e2 = { 1 };
+ E e3 = { 1, 2};
+ if (e1.x != 0 || e1.x != e1.y)
+ __builtin_abort();
+ if (e2.x != 1 || e2.x != e2.y)
+ __builtin_abort();
+ if (e3.x != 1 || e3.y != 2)
+ __builtin_abort();
+}
new file mode 100644
@@ -0,0 +1,80 @@
+// PR c++/100252
+// { dg-do run { target c++14 } }
+
+struct A {
+ int x;
+ int y = x;
+};
+
+struct B {
+ int x = 0;
+ int y = A{x}.y;
+};
+
+static void
+test_b (B b1 = B{}, B b2 = B{1}, B b3 = B{1, 2})
+{
+ if (b1.x != 0 || b1.y != b1.x)
+ __builtin_abort();
+ if (b2.x != 1 || b2.y != b2.x)
+ __builtin_abort();
+ if (b3.x != 1 || b3.y != 2)
+ __builtin_abort();
+}
+
+struct C {
+ int x = 0;
+ int y = (true, A{x}.y) + (A{x}.y, 0);
+};
+
+static void
+test_c (C c1 = C{}, C c2 = C{1}, C c3 = C{1, 2})
+{
+ if (c1.x != 0 || c1.y != c1.x)
+ __builtin_abort();
+ if (c2.x != 1 || c2.y != c2.x)
+ __builtin_abort();
+ if (c3.x != 1 || c3.y != 2)
+ __builtin_abort();
+}
+
+struct D {
+ int x = 0;
+ int y = (A{x}.y);
+};
+
+static void
+test_d (D d1 = D{}, D d2 = D{1}, D d3 = D{1, 2})
+{
+ if (d1.x != 0 || d1.y != d1.x)
+ __builtin_abort();
+ if (d2.x != 1 || d2.y != d2.x)
+ __builtin_abort();
+ if (d3.x != 1 || d3.y != 2)
+ __builtin_abort();
+}
+
+struct E {
+ int x = 0;
+ int y = x ? A{x}.y : A{x}.y;
+};
+
+static void
+test_e (E e1 = E{}, E e2 = E{1}, E e3 = E{1, 2})
+{
+ if (e1.x != 0 || e1.y != e1.x)
+ __builtin_abort();
+ if (e2.x != 1 || e2.y != e2.x)
+ __builtin_abort();
+ if (e3.x != 1 || e3.y != 2)
+ __builtin_abort();
+}
+
+int
+main ()
+{
+ test_b ();
+ test_c ();
+ test_d ();
+ test_e ();
+}
new file mode 100644
@@ -0,0 +1,58 @@
+// PR c++/100252
+// { dg-do compile { target c++14 } }
+
+#define SA(X) static_assert ((X),#X)
+
+struct A {
+ const A* p = this;
+};
+
+struct B {
+ A a = A{};
+};
+
+constexpr B b;
+SA(b.a.p == &b.a);
+B b1 = { };
+
+struct C {
+ A a = (true, A{});
+};
+
+constexpr C c;
+SA(c.a.p == &c.a);
+C c1 = { };
+
+struct D {
+ A a = (A{});
+};
+
+constexpr D d;
+SA(d.a.p == &d.a);
+D d1 = { };
+
+static constexpr A global_a;
+
+struct E {
+ A a = true ? A{} : A{};
+ A b = true ? global_a : (false ? A{} : A{});
+ A c = true ? (false ? A{} : A{}) : global_a;
+ A d = true ? (false ? A{} : A{}) : (false ? A{} : A{});
+};
+
+// FIXME: When fixing this, also fix nsdmi-aggr17.C.
+constexpr E e; // { dg-bogus "" "PR105550" { xfail *-*-* } }
+SA (e.a.p == &e.a); // { dg-bogus "" "PR105550" { xfail *-*-* } }
+
+E e1 = { };
+
+struct F {
+ bool b = (A{}, true);
+};
+
+constexpr F f;
+
+void
+g (B b2 = B{}, C c2 = C{}, D d2 = D{}, E e2 = E{})
+{
+}
new file mode 100644
@@ -0,0 +1,138 @@
+// PR c++/100252
+// { dg-do run { target c++14 } }
+
+#define SA(X) static_assert ((X),#X)
+
+struct A {
+ int x;
+ int y = x;
+ const A* p = this;
+};
+
+struct B {
+ int x = 42;
+ A a = A{x};
+};
+
+constexpr B b;
+SA(b.a.p == &b.a);
+SA(b.x == 42);
+B b2 = { };
+B b3 = { 42 };
+
+struct C {
+ int x = 42;
+ B b = B{x};
+};
+
+constexpr C c;
+C c2;
+C c3;
+
+struct D {
+ int x = 42;
+ A a = (true, A{x});
+};
+
+constexpr D d;
+SA(d.a.p == &d.a);
+SA(d.x == 42);
+D d2 = { };
+D d3 = { 42 };
+
+struct E {
+ int x = 42;
+ A a = (A{x});
+};
+
+constexpr E e;
+SA(e.a.p == &e.a);
+SA(e.x == 42);
+E e2 = { };
+E e3 = { 42 };
+
+struct F {
+ int x = 42;
+ A a = true ? A{x} : A{x};
+};
+
+// FIXME: Doesn't work due to PR105550.
+//constexpr F f;
+//SA (f.a.p == &f.a);
+SA (e.x == 42);
+F f2 = { };
+F f3 = { 42 };
+
+static void
+test_b (B b4 = B{}, B b5 = B{ 42 })
+{
+ if (b2.x != 42 || b2.a.x != 42 || b2.a.y != b2.a.x)
+ __builtin_abort ();
+ if (b3.x != 42 || b3.a.x != 42 || b3.a.y != b3.a.x)
+ __builtin_abort ();
+ if (b4.x != 42 || b4.a.x != 42 || b4.a.y != b4.a.x)
+ __builtin_abort ();
+ if (b5.x != 42 || b5.a.x != 42 || b5.a.y != b5.a.x)
+ __builtin_abort ();
+}
+
+static void
+test_c (C c4 = C{}, C c5 = C{ 42 })
+{
+ if (c2.b.x != 42 || c2.b.a.x != 42 || c2.b.a.y != c2.b.a.x)
+ __builtin_abort ();
+ if (c3.b.x != 42 || c3.b.a.x != 42 || c3.b.a.y != c3.b.a.x)
+ __builtin_abort ();
+ if (c4.b.x != 42 || c4.b.a.x != 42 || c4.b.a.y != c4.b.a.x)
+ __builtin_abort ();
+ if (c5.b.x != 42 || c5.b.a.x != 42 || c5.b.a.y != c5.b.a.x)
+ __builtin_abort ();
+}
+
+static void
+test_d (D d4 = D{}, D d5 = D{ 42 })
+{
+ if (d2.x != 42 || d2.a.x != 42 || d2.a.y != d2.a.x)
+ __builtin_abort ();
+ if (d3.x != 42 || d3.a.x != 42 || d3.a.y != d3.a.x)
+ __builtin_abort ();
+ if (d4.x != 42 || d4.a.x != 42 || d4.a.y != d4.a.x)
+ __builtin_abort ();
+ if (d5.x != 42 || d5.a.x != 42 || d5.a.y != d5.a.x)
+ __builtin_abort ();
+}
+
+static void
+test_e (E e4 = E{}, E e5 = E{ 42 })
+{
+ if (e2.x != 42 || e2.a.x != 42 || e2.a.y != e2.a.x)
+ __builtin_abort ();
+ if (e3.x != 42 || e3.a.x != 42 || e3.a.y != e3.a.x)
+ __builtin_abort ();
+ if (e4.x != 42 || e4.a.x != 42 || e4.a.y != e4.a.x)
+ __builtin_abort ();
+ if (e5.x != 42 || e5.a.x != 42 || e5.a.y != e5.a.x)
+ __builtin_abort ();
+}
+
+static void
+test_f (F f4 = F{}, F f5 = F{ 42 })
+{
+ if (f2.x != 42 || f2.a.x != 42 || f2.a.y != f2.a.x)
+ __builtin_abort ();
+ if (f3.x != 42 || f3.a.x != 42 || f3.a.y != f3.a.x)
+ __builtin_abort ();
+ if (f4.x != 42 || f4.a.x != 42 || f4.a.y != f4.a.x)
+ __builtin_abort ();
+ if (f5.x != 42 || f5.a.x != 42 || f5.a.y != f5.a.x)
+ __builtin_abort ();
+}
+int
+main ()
+{
+ test_b ();
+ test_c ();
+ test_d ();
+ test_e ();
+ test_f ();
+}
new file mode 100644
@@ -0,0 +1,56 @@
+// PR c++/100252
+// { dg-do compile { target c++14 } }
+
+struct B { };
+
+struct A {
+ int x;
+ int y = x;
+ constexpr operator B() { return B{}; }
+};
+
+struct C {
+ int x = 42;
+ B b = A{x};
+};
+
+C c1 = {};
+C c2 = { 42 };
+constexpr C c3 = {};
+constexpr C c4 = { 42 };
+
+struct D {
+ int x = 42;
+ B b = (true, A{x});
+};
+
+D d1 = {};
+D d2 = { 42 };
+constexpr D d3 = {};
+constexpr D d4 = { 42 };
+
+struct E {
+ int x = 42;
+ B b = (A{x});
+};
+
+E e1 = {};
+E e2 = { 42 };
+constexpr E e3 = {};
+constexpr E e4 = { 42 };
+
+struct F {
+ int x = 42;
+ B b = (A{x});
+};
+
+F f1 = {};
+F f2 = { 42 };
+constexpr F f3 = {};
+constexpr F f4 = { 42 };
+
+void
+g (C c5 = C{}, C c6 = C{ 42 }, D d5 = D{}, D d6 = D{ 42 },
+ E e5 = E{}, E e6 = E{ 42 }, F f5 = F{}, F f6 = F{ 42 })
+{
+}
new file mode 100644
@@ -0,0 +1,28 @@
+// PR c++/100252
+// { dg-do compile { target c++14 } }
+
+#define SA(X) static_assert ((X),#X)
+
+struct A {
+ const A* p = this;
+};
+
+struct B {
+ A a = (A{}, A{});
+};
+
+constexpr B b;
+SA(b.a.p == &b.a);
+
+struct C {
+ int x;
+ int y = x;
+};
+
+struct D {
+ int x = 0;
+ int y = (C{x}.y, C{x}.y);
+};
+
+constexpr D d = { };
+D d2 = {};