Re: [PATCH] c++: noexcept and copy elision [PR109030]
On 3/16/23 11:48, Patrick Palka wrote:
On Thu, 16 Mar 2023, Jason Merrill wrote:
On 3/16/23 10:09, Patrick Palka wrote:
On Wed, 15 Mar 2023, Patrick Palka wrote:
On Thu, 9 Mar 2023, Jason Merrill wrote:
On 3/9/23 14:32, Patrick Palka wrote:
On Mon, 6 Mar 2023, Marek Polacek via Gcc-patches wrote:
When processing a noexcept, constructors aren't elided:
build_over_call
has
/* It's unsafe to elide the constructor when handling
a noexcept-expression, it may evaluate to the wrong
value (c++/53025). */
&& (force_elide || cp_noexcept_operand == 0))
so the assert I added recently needs to be relaxed a little bit.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/109030
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_call_expression): Relax assert.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept77.C: New test.
---
gcc/cp/constexpr.cc | 6 +-
gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
2 files changed, 14 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 364695b762c..5384d0e8e46 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx
*ctx,
tree t,
/* We used to shortcut trivial constructor/op= here, but
nowadays
we can only get a trivial function here with
-fno-elide-constructors. */
- gcc_checking_assert (!trivial_fn_p (fun) ||
!flag_elide_constructors);
+ gcc_checking_assert (!trivial_fn_p (fun)
+ || !flag_elide_constructors
+ /* We don't elide constructors when processing
+ a noexcept-expression. */
+ || cp_noexcept_operand);
It seems weird that we're performing constant evaluation within an
unevaluated operand. Would it make sense to also fix this a second
way
by avoiding constant evaluation from maybe_constant_init when
cp_unevaluated_operand && !manifestly_const_eval, like in
maybe_constant_value?
Sounds good.
Hmm, while working on this I noticed we currently don't reject a version
of
g++.dg/cpp2a/constexpr-inst1.C that list initializes an aggregate instead
of
int (ever since r12-4425-g1595fe44e11a96):
struct A { int m; };
template constexpr int f() { return T::value; }
template void h(decltype(A{B ? f() : 0})); //
was int{...}
template void h(...);
void x() {
h(0); // OK?
}
ISTM we should instantiate f here for the same reason we do in the
original version of the testcase, and for that to happen we need to
pass manifestly_const_eval=true in massage_init_elt. Does that seem
reasonable?
FWIW the reason this came up is because I tried contriving a testcase
for the aforementioned maybe_constant_init change, and I came up with:
struct __as_receiver {
int empty_env;
};
template
constexpr int f(T t) {
return t.fail;
};
using type = decltype(__as_receiver{f(0)}); // OK, f no longer
instantiated
which we used to reject and afterwards accept. But since the elements
of an initializer list are potentially constant evaluated, I wonder if
that that means f should be instantiated here after all despite the
unevaluated context?
The relevant section of the standard would seem to be
https://eel.is/c++draft/expr.const#20 ; an immediate subexpression of a
braced-init-list is potentially constant-evaluated even though it isn't
potentially-evaluated or manifestly constant-evaluated.
It seems like the call to fold_non_dependent_expr in check_narrowing ought to
cause instantiation in this case, why doesn't it?
Looks like check_narrowing isn't called at all in this aggr init case.
The call from e.g. convert_like_internal isn't reached because the
conversion for the initializer element is ck_identity, and don't ever
set conversion::check_narrowing for ck_identity conversions I think.
Ah, yes, that makes sense; an identity conversion can never be
narrowing, so we don't care about the constant value. So not
instantiating seems correct, and the patch is OK.
Yet for using 'type = decltype(int{f(0)});' (similar to the example in
[temp.inst]/8) we do call check_narrowing directly from
finish_compound_literal, despite the conversion effectively being an
identity conversion.
Hmm, maybe check_narrowing should defer constant evaluation until after
deciding that the target type is not a superset of the source type...
Here's the full patch for reference:
-- >8 --
Subject: [PATCH] c++: maybe_constant_init and unevaluated operands
[PR109030]
This testcase in this PR (already fixed by r13-6526-ge4692319fd5fc7)
illustrates that maybe_constant_init can be called on an unevaluated
operand (from massage_init_elt), so this entry point should limit
constant evaluation in that case, like maybe_constant_value does.
PR c++/10
Re: [PATCH] c++: noexcept and copy elision [PR109030]
On Thu, 16 Mar 2023, Jason Merrill wrote:
> On 3/16/23 10:09, Patrick Palka wrote:
> > On Wed, 15 Mar 2023, Patrick Palka wrote:
> >
> > > On Thu, 9 Mar 2023, Jason Merrill wrote:
> > >
> > > > On 3/9/23 14:32, Patrick Palka wrote:
> > > > > On Mon, 6 Mar 2023, Marek Polacek via Gcc-patches wrote:
> > > > >
> > > > > > When processing a noexcept, constructors aren't elided:
> > > > > > build_over_call
> > > > > > has
> > > > > > /* It's unsafe to elide the constructor when handling
> > > > > > a noexcept-expression, it may evaluate to the wrong
> > > > > > value (c++/53025). */
> > > > > > && (force_elide || cp_noexcept_operand == 0))
> > > > > > so the assert I added recently needs to be relaxed a little bit.
> > > > > >
> > > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > > > > >
> > > > > > PR c++/109030
> > > > > >
> > > > > > gcc/cp/ChangeLog:
> > > > > >
> > > > > > * constexpr.cc (cxx_eval_call_expression): Relax assert.
> > > > > >
> > > > > > gcc/testsuite/ChangeLog:
> > > > > >
> > > > > > * g++.dg/cpp0x/noexcept77.C: New test.
> > > > > > ---
> > > > > >gcc/cp/constexpr.cc | 6 +-
> > > > > >gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
> > > > > >2 files changed, 14 insertions(+), 1 deletion(-)
> > > > > >create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
> > > > > >
> > > > > > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> > > > > > index 364695b762c..5384d0e8e46 100644
> > > > > > --- a/gcc/cp/constexpr.cc
> > > > > > +++ b/gcc/cp/constexpr.cc
> > > > > > @@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx
> > > > > > *ctx,
> > > > > > tree t,
> > > > > >/* We used to shortcut trivial constructor/op= here, but
> > > > > > nowadays
> > > > > > we can only get a trivial function here with
> > > > > > -fno-elide-constructors. */
> > > > > > - gcc_checking_assert (!trivial_fn_p (fun) ||
> > > > > > !flag_elide_constructors);
> > > > > > + gcc_checking_assert (!trivial_fn_p (fun)
> > > > > > + || !flag_elide_constructors
> > > > > > + /* We don't elide constructors when processing
> > > > > > + a noexcept-expression. */
> > > > > > + || cp_noexcept_operand);
> > > > >
> > > > > It seems weird that we're performing constant evaluation within an
> > > > > unevaluated operand. Would it make sense to also fix this a second
> > > > > way
> > > > > by avoiding constant evaluation from maybe_constant_init when
> > > > > cp_unevaluated_operand && !manifestly_const_eval, like in
> > > > > maybe_constant_value?
> > > >
> > > > Sounds good.
> > >
> > > Hmm, while working on this I noticed we currently don't reject a version
> > > of
> > > g++.dg/cpp2a/constexpr-inst1.C that list initializes an aggregate instead
> > > of
> > > int (ever since r12-4425-g1595fe44e11a96):
> > >
> > >struct A { int m; };
> > >template constexpr int f() { return T::value; }
> > >template void h(decltype(A{B ? f() : 0})); //
> > > was int{...}
> > >template void h(...);
> > >void x() {
> > > h(0); // OK?
> > >}
> > >
> > > ISTM we should instantiate f here for the same reason we do in the
> > > original version of the testcase, and for that to happen we need to
> > > pass manifestly_const_eval=true in massage_init_elt. Does that seem
> > > reasonable?
> > >
> >
> > FWIW the reason this came up is because I tried contriving a testcase
> > for the aforementioned maybe_constant_init change, and I came up with:
> >
> >struct __as_receiver {
> > int empty_env;
> >};
> >
> >template
> >constexpr int f(T t) {
> > return t.fail;
> >};
> >
> >using type = decltype(__as_receiver{f(0)}); // OK, f no longer
> > instantiated
> >
> > which we used to reject and afterwards accept. But since the elements
> > of an initializer list are potentially constant evaluated, I wonder if
> > that that means f should be instantiated here after all despite the
> > unevaluated context?
>
> The relevant section of the standard would seem to be
> https://eel.is/c++draft/expr.const#20 ; an immediate subexpression of a
> braced-init-list is potentially constant-evaluated even though it isn't
> potentially-evaluated or manifestly constant-evaluated.
>
> It seems like the call to fold_non_dependent_expr in check_narrowing ought to
> cause instantiation in this case, why doesn't it?
Looks like check_narrowing isn't called at all in this aggr init case.
The call from e.g. convert_like_internal isn't reached because the
conversion for the initializer element is ck_identity, and don't ever
set conversion::check_narrowing for ck_identity conversions I think.
Yet for using 'type = decltype(int{f(0)});' (similar to the example in
[temp.inst]/8) we do call check_narrowing directly from
finish_compound_literal, despite the conversion effectively being
Re: [PATCH] c++: noexcept and copy elision [PR109030]
On 3/16/23 10:09, Patrick Palka wrote:
On Wed, 15 Mar 2023, Patrick Palka wrote:
On Thu, 9 Mar 2023, Jason Merrill wrote:
On 3/9/23 14:32, Patrick Palka wrote:
On Mon, 6 Mar 2023, Marek Polacek via Gcc-patches wrote:
When processing a noexcept, constructors aren't elided: build_over_call
has
/* It's unsafe to elide the constructor when handling
a noexcept-expression, it may evaluate to the wrong
value (c++/53025). */
&& (force_elide || cp_noexcept_operand == 0))
so the assert I added recently needs to be relaxed a little bit.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/109030
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_call_expression): Relax assert.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept77.C: New test.
---
gcc/cp/constexpr.cc | 6 +-
gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
2 files changed, 14 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 364695b762c..5384d0e8e46 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx *ctx,
tree t,
/* We used to shortcut trivial constructor/op= here, but nowadays
we can only get a trivial function here with
-fno-elide-constructors. */
- gcc_checking_assert (!trivial_fn_p (fun) || !flag_elide_constructors);
+ gcc_checking_assert (!trivial_fn_p (fun)
+ || !flag_elide_constructors
+ /* We don't elide constructors when processing
+ a noexcept-expression. */
+ || cp_noexcept_operand);
It seems weird that we're performing constant evaluation within an
unevaluated operand. Would it make sense to also fix this a second way
by avoiding constant evaluation from maybe_constant_init when
cp_unevaluated_operand && !manifestly_const_eval, like in
maybe_constant_value?
Sounds good.
Hmm, while working on this I noticed we currently don't reject a version of
g++.dg/cpp2a/constexpr-inst1.C that list initializes an aggregate instead of
int (ever since r12-4425-g1595fe44e11a96):
struct A { int m; };
template constexpr int f() { return T::value; }
template void h(decltype(A{B ? f() : 0})); // was
int{...}
template void h(...);
void x() {
h(0); // OK?
}
ISTM we should instantiate f here for the same reason we do in the
original version of the testcase, and for that to happen we need to
pass manifestly_const_eval=true in massage_init_elt. Does that seem
reasonable?
FWIW the reason this came up is because I tried contriving a testcase
for the aforementioned maybe_constant_init change, and I came up with:
struct __as_receiver {
int empty_env;
};
template
constexpr int f(T t) {
return t.fail;
};
using type = decltype(__as_receiver{f(0)}); // OK, f no longer
instantiated
which we used to reject and afterwards accept. But since the elements
of an initializer list are potentially constant evaluated, I wonder if
that that means f should be instantiated here after all despite the
unevaluated context?
The relevant section of the standard would seem to be
https://eel.is/c++draft/expr.const#20 ; an immediate subexpression of a
braced-init-list is potentially constant-evaluated even though it isn't
potentially-evaluated or manifestly constant-evaluated.
It seems like the call to fold_non_dependent_expr in check_narrowing
ought to cause instantiation in this case, why doesn't it?
Here's the full patch for reference:
-- >8 --
Subject: [PATCH] c++: maybe_constant_init and unevaluated operands [PR109030]
This testcase in this PR (already fixed by r13-6526-ge4692319fd5fc7)
illustrates that maybe_constant_init can be called on an unevaluated
operand (from massage_init_elt), so this entry point should limit
constant evaluation in that case, like maybe_constant_value does.
PR c++/109030
gcc/cp/ChangeLog:
* constexpr.cc (maybe_constant_init_1): For an unevaluated
non-manifestly-constant operand, don't constant evaluate
and instead call fold_to_constant.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/decltype83.C: New test.
---
gcc/cp/constexpr.cc | 2 ++
gcc/testsuite/g++.dg/cpp0x/decltype83.C | 14 ++
2 files changed, 16 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/decltype83.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 8683c00596a..f325af375c8 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -8795,6 +8795,8 @@ maybe_constant_init_1 (tree t, tree decl, bool
allow_non_constant,
&& (TREE_STATIC (decl) || DECL_EXTERNAL (decl)));
if (is_static)
manifestly_const_eval = true;
+ if (cp_unevaluated_operand && !manifestly_const_eval)
+
Re: [PATCH] c++: noexcept and copy elision [PR109030]
On Wed, 15 Mar 2023, Patrick Palka wrote:
> On Thu, 9 Mar 2023, Jason Merrill wrote:
>
> > On 3/9/23 14:32, Patrick Palka wrote:
> > > On Mon, 6 Mar 2023, Marek Polacek via Gcc-patches wrote:
> > >
> > > > When processing a noexcept, constructors aren't elided: build_over_call
> > > > has
> > > > /* It's unsafe to elide the constructor when handling
> > > > a noexcept-expression, it may evaluate to the wrong
> > > > value (c++/53025). */
> > > > && (force_elide || cp_noexcept_operand == 0))
> > > > so the assert I added recently needs to be relaxed a little bit.
> > > >
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > > >
> > > > PR c++/109030
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > > * constexpr.cc (cxx_eval_call_expression): Relax assert.
> > > >
> > > > gcc/testsuite/ChangeLog:
> > > >
> > > > * g++.dg/cpp0x/noexcept77.C: New test.
> > > > ---
> > > > gcc/cp/constexpr.cc | 6 +-
> > > > gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
> > > > 2 files changed, 14 insertions(+), 1 deletion(-)
> > > > create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
> > > >
> > > > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> > > > index 364695b762c..5384d0e8e46 100644
> > > > --- a/gcc/cp/constexpr.cc
> > > > +++ b/gcc/cp/constexpr.cc
> > > > @@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx
> > > > *ctx,
> > > > tree t,
> > > > /* We used to shortcut trivial constructor/op= here, but nowadays
> > > >we can only get a trivial function here with
> > > > -fno-elide-constructors. */
> > > > - gcc_checking_assert (!trivial_fn_p (fun) ||
> > > > !flag_elide_constructors);
> > > > + gcc_checking_assert (!trivial_fn_p (fun)
> > > > + || !flag_elide_constructors
> > > > + /* We don't elide constructors when processing
> > > > + a noexcept-expression. */
> > > > + || cp_noexcept_operand);
> > >
> > > It seems weird that we're performing constant evaluation within an
> > > unevaluated operand. Would it make sense to also fix this a second way
> > > by avoiding constant evaluation from maybe_constant_init when
> > > cp_unevaluated_operand && !manifestly_const_eval, like in
> > > maybe_constant_value?
> >
> > Sounds good.
>
> Hmm, while working on this I noticed we currently don't reject a version of
> g++.dg/cpp2a/constexpr-inst1.C that list initializes an aggregate instead of
> int (ever since r12-4425-g1595fe44e11a96):
>
> struct A { int m; };
> template constexpr int f() { return T::value; }
> template void h(decltype(A{B ? f() : 0})); // was
> int{...}
> template void h(...);
> void x() {
> h(0); // OK?
> }
>
> ISTM we should instantiate f here for the same reason we do in the
> original version of the testcase, and for that to happen we need to
> pass manifestly_const_eval=true in massage_init_elt. Does that seem
> reasonable?
>
FWIW the reason this came up is because I tried contriving a testcase
for the aforementioned maybe_constant_init change, and I came up with:
struct __as_receiver {
int empty_env;
};
template
constexpr int f(T t) {
return t.fail;
};
using type = decltype(__as_receiver{f(0)}); // OK, f no longer
instantiated
which we used to reject and afterwards accept. But since the elements
of an initializer list are potentially constant evaluated, I wonder if
that that means f should be instantiated here after all despite the
unevaluated context?
Here's the full patch for reference:
-- >8 --
Subject: [PATCH] c++: maybe_constant_init and unevaluated operands [PR109030]
This testcase in this PR (already fixed by r13-6526-ge4692319fd5fc7)
illustrates that maybe_constant_init can be called on an unevaluated
operand (from massage_init_elt), so this entry point should limit
constant evaluation in that case, like maybe_constant_value does.
PR c++/109030
gcc/cp/ChangeLog:
* constexpr.cc (maybe_constant_init_1): For an unevaluated
non-manifestly-constant operand, don't constant evaluate
and instead call fold_to_constant.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/decltype83.C: New test.
---
gcc/cp/constexpr.cc | 2 ++
gcc/testsuite/g++.dg/cpp0x/decltype83.C | 14 ++
2 files changed, 16 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/decltype83.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 8683c00596a..f325af375c8 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -8795,6 +8795,8 @@ maybe_constant_init_1 (tree t, tree decl, bool
allow_non_constant,
&& (TREE_STATIC (decl) || DECL_EXTERNAL (decl)));
if (is_static)
manifestly_const_eval = true;
+ if (cp_unevaluated_operand && !manifestly_const_eval)
+ return fold_to_consta
Re: [PATCH] c++: noexcept and copy elision [PR109030]
On Thu, 9 Mar 2023, Jason Merrill wrote:
> On 3/9/23 14:32, Patrick Palka wrote:
> > On Mon, 6 Mar 2023, Marek Polacek via Gcc-patches wrote:
> >
> > > When processing a noexcept, constructors aren't elided: build_over_call
> > > has
> > >/* It's unsafe to elide the constructor when handling
> > > a noexcept-expression, it may evaluate to the wrong
> > > value (c++/53025). */
> > >&& (force_elide || cp_noexcept_operand == 0))
> > > so the assert I added recently needs to be relaxed a little bit.
> > >
> > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > >
> > > PR c++/109030
> > >
> > > gcc/cp/ChangeLog:
> > >
> > > * constexpr.cc (cxx_eval_call_expression): Relax assert.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > > * g++.dg/cpp0x/noexcept77.C: New test.
> > > ---
> > > gcc/cp/constexpr.cc | 6 +-
> > > gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
> > > 2 files changed, 14 insertions(+), 1 deletion(-)
> > > create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
> > >
> > > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> > > index 364695b762c..5384d0e8e46 100644
> > > --- a/gcc/cp/constexpr.cc
> > > +++ b/gcc/cp/constexpr.cc
> > > @@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx *ctx,
> > > tree t,
> > > /* We used to shortcut trivial constructor/op= here, but nowadays
> > >we can only get a trivial function here with
> > > -fno-elide-constructors. */
> > > - gcc_checking_assert (!trivial_fn_p (fun) || !flag_elide_constructors);
> > > + gcc_checking_assert (!trivial_fn_p (fun)
> > > +|| !flag_elide_constructors
> > > +/* We don't elide constructors when processing
> > > + a noexcept-expression. */
> > > +|| cp_noexcept_operand);
> >
> > It seems weird that we're performing constant evaluation within an
> > unevaluated operand. Would it make sense to also fix this a second way
> > by avoiding constant evaluation from maybe_constant_init when
> > cp_unevaluated_operand && !manifestly_const_eval, like in
> > maybe_constant_value?
>
> Sounds good.
Hmm, while working on this I noticed we currently don't reject a version of
g++.dg/cpp2a/constexpr-inst1.C that list initializes an aggregate instead of
int (ever since r12-4425-g1595fe44e11a96):
struct A { int m; };
template constexpr int f() { return T::value; }
template void h(decltype(A{B ? f() : 0})); // was
int{...}
template void h(...);
void x() {
h(0); // OK?
}
ISTM we should instantiate f here for the same reason we do in the
original version of the testcase, and for that to happen we need to
pass manifestly_const_eval=true in massage_init_elt. Does that seem
reasonable?
Re: [PATCH] c++: noexcept and copy elision [PR109030]
On 3/9/23 14:32, Patrick Palka wrote:
On Mon, 6 Mar 2023, Marek Polacek via Gcc-patches wrote:
When processing a noexcept, constructors aren't elided: build_over_call
has
/* It's unsafe to elide the constructor when handling
a noexcept-expression, it may evaluate to the wrong
value (c++/53025). */
&& (force_elide || cp_noexcept_operand == 0))
so the assert I added recently needs to be relaxed a little bit.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/109030
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_call_expression): Relax assert.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept77.C: New test.
---
gcc/cp/constexpr.cc | 6 +-
gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
2 files changed, 14 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 364695b762c..5384d0e8e46 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree
t,
/* We used to shortcut trivial constructor/op= here, but nowadays
we can only get a trivial function here with -fno-elide-constructors. */
- gcc_checking_assert (!trivial_fn_p (fun) || !flag_elide_constructors);
+ gcc_checking_assert (!trivial_fn_p (fun)
+ || !flag_elide_constructors
+ /* We don't elide constructors when processing
+ a noexcept-expression. */
+ || cp_noexcept_operand);
It seems weird that we're performing constant evaluation within an
unevaluated operand. Would it make sense to also fix this a second way
by avoiding constant evaluation from maybe_constant_init when
cp_unevaluated_operand && !manifestly_const_eval, like in maybe_constant_value?
Sounds good.
IIUC since we could still have an evaluated subexpression withis
noexcept, the two fixes would be complementary.
bool non_constant_args = false;
new_call.bindings
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
new file mode 100644
index 000..16db8eb79ee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
@@ -0,0 +1,9 @@
+// PR c++/109030
+// { dg-do compile { target c++11 } }
+
+struct foo { };
+
+struct __as_receiver {
+ foo empty_env;
+};
+void sched(foo __fun) noexcept(noexcept(__as_receiver{__fun})) { }
base-commit: dfb14cdd796ad9df6b5f2def047ef36b29385902
--
2.39.2
Re: [PATCH] c++: noexcept and copy elision [PR109030]
On Mon, 6 Mar 2023, Marek Polacek via Gcc-patches wrote:
> When processing a noexcept, constructors aren't elided: build_over_call
> has
>/* It's unsafe to elide the constructor when handling
> a noexcept-expression, it may evaluate to the wrong
> value (c++/53025). */
>&& (force_elide || cp_noexcept_operand == 0))
> so the assert I added recently needs to be relaxed a little bit.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
> PR c++/109030
>
> gcc/cp/ChangeLog:
>
> * constexpr.cc (cxx_eval_call_expression): Relax assert.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp0x/noexcept77.C: New test.
> ---
> gcc/cp/constexpr.cc | 6 +-
> gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
> 2 files changed, 14 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
>
> diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> index 364695b762c..5384d0e8e46 100644
> --- a/gcc/cp/constexpr.cc
> +++ b/gcc/cp/constexpr.cc
> @@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx *ctx,
> tree t,
>
>/* We used to shortcut trivial constructor/op= here, but nowadays
> we can only get a trivial function here with -fno-elide-constructors.
> */
> - gcc_checking_assert (!trivial_fn_p (fun) || !flag_elide_constructors);
> + gcc_checking_assert (!trivial_fn_p (fun)
> +|| !flag_elide_constructors
> +/* We don't elide constructors when processing
> + a noexcept-expression. */
> +|| cp_noexcept_operand);
It seems weird that we're performing constant evaluation within an
unevaluated operand. Would it make sense to also fix this a second way
by avoiding constant evaluation from maybe_constant_init when
cp_unevaluated_operand && !manifestly_const_eval, like in maybe_constant_value?
IIUC since we could still have an evaluated subexpression withis
noexcept, the two fixes would be complementary.
>
>bool non_constant_args = false;
>new_call.bindings
> diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
> b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
> new file mode 100644
> index 000..16db8eb79ee
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
> @@ -0,0 +1,9 @@
> +// PR c++/109030
> +// { dg-do compile { target c++11 } }
> +
> +struct foo { };
> +
> +struct __as_receiver {
> + foo empty_env;
> +};
> +void sched(foo __fun) noexcept(noexcept(__as_receiver{__fun})) { }
>
> base-commit: dfb14cdd796ad9df6b5f2def047ef36b29385902
> --
> 2.39.2
>
>
Re: [PATCH] c++: noexcept and copy elision [PR109030]
On 3/6/23 18:59, Marek Polacek wrote:
When processing a noexcept, constructors aren't elided: build_over_call
has
/* It's unsafe to elide the constructor when handling
a noexcept-expression, it may evaluate to the wrong
value (c++/53025). */
&& (force_elide || cp_noexcept_operand == 0))
so the assert I added recently needs to be relaxed a little bit.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
OK.
PR c++/109030
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_call_expression): Relax assert.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept77.C: New test.
---
gcc/cp/constexpr.cc | 6 +-
gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
2 files changed, 14 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 364695b762c..5384d0e8e46 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree
t,
/* We used to shortcut trivial constructor/op= here, but nowadays
we can only get a trivial function here with -fno-elide-constructors. */
- gcc_checking_assert (!trivial_fn_p (fun) || !flag_elide_constructors);
+ gcc_checking_assert (!trivial_fn_p (fun)
+ || !flag_elide_constructors
+ /* We don't elide constructors when processing
+ a noexcept-expression. */
+ || cp_noexcept_operand);
bool non_constant_args = false;
new_call.bindings
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
new file mode 100644
index 000..16db8eb79ee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
@@ -0,0 +1,9 @@
+// PR c++/109030
+// { dg-do compile { target c++11 } }
+
+struct foo { };
+
+struct __as_receiver {
+ foo empty_env;
+};
+void sched(foo __fun) noexcept(noexcept(__as_receiver{__fun})) { }
base-commit: dfb14cdd796ad9df6b5f2def047ef36b29385902
[PATCH] c++: noexcept and copy elision [PR109030]
When processing a noexcept, constructors aren't elided: build_over_call
has
/* It's unsafe to elide the constructor when handling
a noexcept-expression, it may evaluate to the wrong
value (c++/53025). */
&& (force_elide || cp_noexcept_operand == 0))
so the assert I added recently needs to be relaxed a little bit.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/109030
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_call_expression): Relax assert.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept77.C: New test.
---
gcc/cp/constexpr.cc | 6 +-
gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +
2 files changed, 14 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 364695b762c..5384d0e8e46 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree
t,
/* We used to shortcut trivial constructor/op= here, but nowadays
we can only get a trivial function here with -fno-elide-constructors. */
- gcc_checking_assert (!trivial_fn_p (fun) || !flag_elide_constructors);
+ gcc_checking_assert (!trivial_fn_p (fun)
+ || !flag_elide_constructors
+ /* We don't elide constructors when processing
+ a noexcept-expression. */
+ || cp_noexcept_operand);
bool non_constant_args = false;
new_call.bindings
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
new file mode 100644
index 000..16db8eb79ee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
@@ -0,0 +1,9 @@
+// PR c++/109030
+// { dg-do compile { target c++11 } }
+
+struct foo { };
+
+struct __as_receiver {
+ foo empty_env;
+};
+void sched(foo __fun) noexcept(noexcept(__as_receiver{__fun})) { }
base-commit: dfb14cdd796ad9df6b5f2def047ef36b29385902
--
2.39.2
