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