* [PATCH] c++: Instantiate less when evaluating __is_convertible @ 2022-09-26 15:22 Marek Polacek 2022-09-26 15:51 ` Patrick Palka 2022-09-26 16:02 ` [PATCH] " Jonathan Wakely 0 siblings, 2 replies; 7+ messages in thread From: Marek Polacek @ 2022-09-26 15:22 UTC (permalink / raw) To: GCC Patches, Jason Merrill; +Cc: Jonathan Wakely Jon reported that evaluating __is_convertible in this test leads to instantiating char_traits<char>::eq, which is invalid (because we are trying to call a member function on a char) and so we fail to compile the test. __is_convertible doesn't and shouldn't need to instantiate so much, so let's limit it with a cp_unevaluated guard. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR c++/106784 gcc/cp/ChangeLog: * method.cc (is_convertible): Use cp_unevaluated. gcc/testsuite/ChangeLog: * g++.dg/ext/is_convertible3.C: New test. --- gcc/cp/method.cc | 1 + gcc/testsuite/g++.dg/ext/is_convertible3.C | 66 ++++++++++++++++++++++ 2 files changed, 67 insertions(+) create mode 100644 gcc/testsuite/g++.dg/ext/is_convertible3.C diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc index c35a59fe56c..45f70f5d3f3 100644 --- a/gcc/cp/method.cc +++ b/gcc/cp/method.cc @@ -2246,6 +2246,7 @@ is_convertible (tree from, tree to) { if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) return true; + cp_unevaluated u; tree expr = build_stub_object (from); expr = perform_implicit_conversion (to, expr, tf_none); if (expr == error_mark_node) diff --git a/gcc/testsuite/g++.dg/ext/is_convertible3.C b/gcc/testsuite/g++.dg/ext/is_convertible3.C new file mode 100644 index 00000000000..c817dc6f146 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/is_convertible3.C @@ -0,0 +1,66 @@ +// PR c++/106784 +// { dg-do compile { target c++11 } } +// Make sure we don't reject this at runtime by trying to instantiate +// char_traits<CharT>::eq(CharT, CharT) while evaluating __is_convertible. + +template<bool B> +struct bool_constant { static constexpr bool value = B; }; +using true_type = bool_constant<true>; +using false_type = bool_constant<false>; + +template<typename T> struct is_void : false_type { }; +template<> struct is_void<void> : true_type { }; + +template<typename T> T&& declval(); + +template<bool> struct enable_if { }; +template<> struct enable_if<true> { using type = void; }; +template<bool B> using enable_if_t = typename enable_if<B>::type; + +template<typename _From, typename _To> + struct is_convertible + : public bool_constant<__is_convertible(_From, _To)> + { }; + +template<class CharT> +struct char_traits +{ + static unsigned long length(const char* s) { eq(*s, *s); return 0; } + + static void eq(CharT l, CharT r) noexcept { l.f(r); } +}; + +template<class CharT> +struct basic_string_view +{ + using traits_type = char_traits<CharT>; + + constexpr basic_string_view() = default; + constexpr basic_string_view(const basic_string_view&) = default; + + constexpr + basic_string_view(const CharT* __str) noexcept + : _M_len{traits_type::length(__str)} + { } + + unsigned long _M_len = 0; +}; + +template<class CharT> +struct basic_string +{ + template<class T> + enable_if_t<is_convertible<const T&, basic_string_view<CharT>>::value + && !is_convertible<const T&, const char*>::value> + replace(int, T) { } + + void replace(unsigned long, const char*) { } + + void replace(const char* s) { replace(1, s); } +}; + +int main() +{ + basic_string<char> s; + s.replace(""); +} base-commit: 2460f7cdef7ef9c971de79271afc0db73687a272 -- 2.37.3 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] c++: Instantiate less when evaluating __is_convertible 2022-09-26 15:22 [PATCH] c++: Instantiate less when evaluating __is_convertible Marek Polacek @ 2022-09-26 15:51 ` Patrick Palka 2022-09-26 16:21 ` Jason Merrill 2022-09-26 16:25 ` [PATCH v2] " Marek Polacek 2022-09-26 16:02 ` [PATCH] " Jonathan Wakely 1 sibling, 2 replies; 7+ messages in thread From: Patrick Palka @ 2022-09-26 15:51 UTC (permalink / raw) To: Marek Polacek; +Cc: GCC Patches, Jason Merrill, Jonathan Wakely On Mon, 26 Sep 2022, Marek Polacek via Gcc-patches wrote: > Jon reported that evaluating __is_convertible in this test leads to > instantiating char_traits<char>::eq, which is invalid (because we > are trying to call a member function on a char) and so we fail to > compile the test. __is_convertible doesn't and shouldn't need to > instantiate so much, so let's limit it with a cp_unevaluated guard. > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > PR c++/106784 > > gcc/cp/ChangeLog: > > * method.cc (is_convertible): Use cp_unevaluated. I think is_nothrow_convertible would need cp_unevaluated too (or maybe we should define is_nothrow_convertible in terms of is_convertible). And the testcase can probably be minimized to something like: struct A; struct B { template<class T> B(const T&) noexcept { T::nonexistent; } }; static_assert(__is_convertible(const A&, B)); static_assert(__is_nothrow_convertible(const A&, B)); > > gcc/testsuite/ChangeLog: > > * g++.dg/ext/is_convertible3.C: New test. > --- > gcc/cp/method.cc | 1 + > gcc/testsuite/g++.dg/ext/is_convertible3.C | 66 ++++++++++++++++++++++ > 2 files changed, 67 insertions(+) > create mode 100644 gcc/testsuite/g++.dg/ext/is_convertible3.C > > diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc > index c35a59fe56c..45f70f5d3f3 100644 > --- a/gcc/cp/method.cc > +++ b/gcc/cp/method.cc > @@ -2246,6 +2246,7 @@ is_convertible (tree from, tree to) > { > if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) > return true; > + cp_unevaluated u; > tree expr = build_stub_object (from); > expr = perform_implicit_conversion (to, expr, tf_none); > if (expr == error_mark_node) > diff --git a/gcc/testsuite/g++.dg/ext/is_convertible3.C b/gcc/testsuite/g++.dg/ext/is_convertible3.C > new file mode 100644 > index 00000000000..c817dc6f146 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/ext/is_convertible3.C > @@ -0,0 +1,66 @@ > +// PR c++/106784 > +// { dg-do compile { target c++11 } } > +// Make sure we don't reject this at runtime by trying to instantiate > +// char_traits<CharT>::eq(CharT, CharT) while evaluating __is_convertible. > + > +template<bool B> > +struct bool_constant { static constexpr bool value = B; }; > +using true_type = bool_constant<true>; > +using false_type = bool_constant<false>; > + > +template<typename T> struct is_void : false_type { }; > +template<> struct is_void<void> : true_type { }; > + > +template<typename T> T&& declval(); > + > +template<bool> struct enable_if { }; > +template<> struct enable_if<true> { using type = void; }; > +template<bool B> using enable_if_t = typename enable_if<B>::type; > + > +template<typename _From, typename _To> > + struct is_convertible > + : public bool_constant<__is_convertible(_From, _To)> > + { }; > + > +template<class CharT> > +struct char_traits > +{ > + static unsigned long length(const char* s) { eq(*s, *s); return 0; } > + > + static void eq(CharT l, CharT r) noexcept { l.f(r); } > +}; > + > +template<class CharT> > +struct basic_string_view > +{ > + using traits_type = char_traits<CharT>; > + > + constexpr basic_string_view() = default; > + constexpr basic_string_view(const basic_string_view&) = default; > + > + constexpr > + basic_string_view(const CharT* __str) noexcept > + : _M_len{traits_type::length(__str)} > + { } > + > + unsigned long _M_len = 0; > +}; > + > +template<class CharT> > +struct basic_string > +{ > + template<class T> > + enable_if_t<is_convertible<const T&, basic_string_view<CharT>>::value > + && !is_convertible<const T&, const char*>::value> > + replace(int, T) { } > + > + void replace(unsigned long, const char*) { } > + > + void replace(const char* s) { replace(1, s); } > +}; > + > +int main() > +{ > + basic_string<char> s; > + s.replace(""); > +} > > base-commit: 2460f7cdef7ef9c971de79271afc0db73687a272 > -- > 2.37.3 > > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] c++: Instantiate less when evaluating __is_convertible 2022-09-26 15:51 ` Patrick Palka @ 2022-09-26 16:21 ` Jason Merrill 2022-09-26 16:25 ` [PATCH v2] " Marek Polacek 1 sibling, 0 replies; 7+ messages in thread From: Jason Merrill @ 2022-09-26 16:21 UTC (permalink / raw) To: Patrick Palka, Marek Polacek; +Cc: GCC Patches, Jonathan Wakely On 9/26/22 11:51, Patrick Palka wrote: > On Mon, 26 Sep 2022, Marek Polacek via Gcc-patches wrote: > >> Jon reported that evaluating __is_convertible in this test leads to >> instantiating char_traits<char>::eq, which is invalid (because we >> are trying to call a member function on a char) and so we fail to >> compile the test. __is_convertible doesn't and shouldn't need to >> instantiate so much, so let's limit it with a cp_unevaluated guard. >> >> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? >> >> PR c++/106784 >> >> gcc/cp/ChangeLog: >> >> * method.cc (is_convertible): Use cp_unevaluated. > > I think is_nothrow_convertible would need cp_unevaluated too (or maybe we > should define is_nothrow_convertible in terms of is_convertible). Agreed. > And the testcase can probably be minimized to something like: > > struct A; > struct B { template<class T> B(const T&) noexcept { T::nonexistent; } }; > > static_assert(__is_convertible(const A&, B)); > static_assert(__is_nothrow_convertible(const A&, B)); > >> >> gcc/testsuite/ChangeLog: >> >> * g++.dg/ext/is_convertible3.C: New test. >> --- >> gcc/cp/method.cc | 1 + >> gcc/testsuite/g++.dg/ext/is_convertible3.C | 66 ++++++++++++++++++++++ >> 2 files changed, 67 insertions(+) >> create mode 100644 gcc/testsuite/g++.dg/ext/is_convertible3.C >> >> diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc >> index c35a59fe56c..45f70f5d3f3 100644 >> --- a/gcc/cp/method.cc >> +++ b/gcc/cp/method.cc >> @@ -2246,6 +2246,7 @@ is_convertible (tree from, tree to) >> { >> if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) >> return true; >> + cp_unevaluated u; >> tree expr = build_stub_object (from); >> expr = perform_implicit_conversion (to, expr, tf_none); >> if (expr == error_mark_node) >> diff --git a/gcc/testsuite/g++.dg/ext/is_convertible3.C b/gcc/testsuite/g++.dg/ext/is_convertible3.C >> new file mode 100644 >> index 00000000000..c817dc6f146 >> --- /dev/null >> +++ b/gcc/testsuite/g++.dg/ext/is_convertible3.C >> @@ -0,0 +1,66 @@ >> +// PR c++/106784 >> +// { dg-do compile { target c++11 } } >> +// Make sure we don't reject this at runtime by trying to instantiate >> +// char_traits<CharT>::eq(CharT, CharT) while evaluating __is_convertible. >> + >> +template<bool B> >> +struct bool_constant { static constexpr bool value = B; }; >> +using true_type = bool_constant<true>; >> +using false_type = bool_constant<false>; >> + >> +template<typename T> struct is_void : false_type { }; >> +template<> struct is_void<void> : true_type { }; >> + >> +template<typename T> T&& declval(); >> + >> +template<bool> struct enable_if { }; >> +template<> struct enable_if<true> { using type = void; }; >> +template<bool B> using enable_if_t = typename enable_if<B>::type; >> + >> +template<typename _From, typename _To> >> + struct is_convertible >> + : public bool_constant<__is_convertible(_From, _To)> >> + { }; >> + >> +template<class CharT> >> +struct char_traits >> +{ >> + static unsigned long length(const char* s) { eq(*s, *s); return 0; } >> + >> + static void eq(CharT l, CharT r) noexcept { l.f(r); } >> +}; >> + >> +template<class CharT> >> +struct basic_string_view >> +{ >> + using traits_type = char_traits<CharT>; >> + >> + constexpr basic_string_view() = default; >> + constexpr basic_string_view(const basic_string_view&) = default; >> + >> + constexpr >> + basic_string_view(const CharT* __str) noexcept >> + : _M_len{traits_type::length(__str)} >> + { } >> + >> + unsigned long _M_len = 0; >> +}; >> + >> +template<class CharT> >> +struct basic_string >> +{ >> + template<class T> >> + enable_if_t<is_convertible<const T&, basic_string_view<CharT>>::value >> + && !is_convertible<const T&, const char*>::value> >> + replace(int, T) { } >> + >> + void replace(unsigned long, const char*) { } >> + >> + void replace(const char* s) { replace(1, s); } >> +}; >> + >> +int main() >> +{ >> + basic_string<char> s; >> + s.replace(""); >> +} >> >> base-commit: 2460f7cdef7ef9c971de79271afc0db73687a272 >> -- >> 2.37.3 >> >> > ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2] c++: Instantiate less when evaluating __is_convertible 2022-09-26 15:51 ` Patrick Palka 2022-09-26 16:21 ` Jason Merrill @ 2022-09-26 16:25 ` Marek Polacek 2022-09-26 16:41 ` Jason Merrill 1 sibling, 1 reply; 7+ messages in thread From: Marek Polacek @ 2022-09-26 16:25 UTC (permalink / raw) To: Patrick Palka; +Cc: GCC Patches, Jason Merrill, Jonathan Wakely On Mon, Sep 26, 2022 at 11:51:30AM -0400, Patrick Palka wrote: > On Mon, 26 Sep 2022, Marek Polacek via Gcc-patches wrote: > > > Jon reported that evaluating __is_convertible in this test leads to > > instantiating char_traits<char>::eq, which is invalid (because we > > are trying to call a member function on a char) and so we fail to > > compile the test. __is_convertible doesn't and shouldn't need to > > instantiate so much, so let's limit it with a cp_unevaluated guard. > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > > > PR c++/106784 > > > > gcc/cp/ChangeLog: > > > > * method.cc (is_convertible): Use cp_unevaluated. > > I think is_nothrow_convertible would need cp_unevaluated too (or maybe we > should define is_nothrow_convertible in terms of is_convertible). /facepalm, that's what I get by not using a single implementation for both! > And the testcase can probably be minimized to something like: > > struct A; > struct B { template<class T> B(const T&) noexcept { T::nonexistent; } }; > > static_assert(__is_convertible(const A&, B)); > static_assert(__is_nothrow_convertible(const A&, B)); Adjusted, thanks. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? -- >8 -- Jon reported that evaluating __is_convertible in a test led to instantiating something ill-formed and so we failed to compile the test. __is_convertible doesn't and shouldn't need to instantiate so much, so let's limit it with a cp_unevaluated guard. Use a helper function to implement both built-ins. PR c++/106784 gcc/cp/ChangeLog: * method.cc (is_convertible_helper): New. (is_convertible): Use it. (is_nothrow_convertible): Likewise. gcc/testsuite/ChangeLog: * g++.dg/ext/is_convertible3.C: New test. * g++.dg/ext/is_nothrow_convertible3.C: New test. --- gcc/cp/method.cc | 23 ++++++++++++------- gcc/testsuite/g++.dg/ext/is_convertible3.C | 9 ++++++++ .../g++.dg/ext/is_nothrow_convertible3.C | 9 ++++++++ 3 files changed, 33 insertions(+), 8 deletions(-) create mode 100644 gcc/testsuite/g++.dg/ext/is_convertible3.C create mode 100644 gcc/testsuite/g++.dg/ext/is_nothrow_convertible3.C diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc index c35a59fe56c..9f917f13134 100644 --- a/gcc/cp/method.cc +++ b/gcc/cp/method.cc @@ -2236,6 +2236,19 @@ ref_xes_from_temporary (tree to, tree from, bool direct_init_p) return ref_conv_binds_directly (to, val, direct_init_p).is_false (); } +/* Worker for is_{,nothrow_}convertible. Attempt to perform an implicit + conversion from FROM to TO and return the result. */ + +static tree +is_convertible_helper (tree from, tree to) +{ + if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) + return integer_one_node; + cp_unevaluated u; + tree expr = build_stub_object (from); + return perform_implicit_conversion (to, expr, tf_none); +} + /* Return true if FROM can be converted to TO using implicit conversions, or both FROM and TO are possibly cv-qualified void. NB: This doesn't implement the "Access checks are performed as if from a context unrelated @@ -2244,10 +2257,7 @@ ref_xes_from_temporary (tree to, tree from, bool direct_init_p) bool is_convertible (tree from, tree to) { - if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) - return true; - tree expr = build_stub_object (from); - expr = perform_implicit_conversion (to, expr, tf_none); + tree expr = is_convertible_helper (from, to); if (expr == error_mark_node) return false; return !!expr; @@ -2258,10 +2268,7 @@ is_convertible (tree from, tree to) bool is_nothrow_convertible (tree from, tree to) { - if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) - return true; - tree expr = build_stub_object (from); - expr = perform_implicit_conversion (to, expr, tf_none); + tree expr = is_convertible_helper (from, to); if (expr == NULL_TREE || expr == error_mark_node) return false; return expr_noexcept_p (expr, tf_none); diff --git a/gcc/testsuite/g++.dg/ext/is_convertible3.C b/gcc/testsuite/g++.dg/ext/is_convertible3.C new file mode 100644 index 00000000000..7a986d075c2 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/is_convertible3.C @@ -0,0 +1,9 @@ +// PR c++/106784 +// { dg-do compile { target c++11 } } +// Make sure we don't reject this at runtime by trying to instantiate +// something that would be ill-formed. + +struct A; +struct B { template<class T> B(const T&) noexcept { T::nonexistent; } }; + +static_assert(__is_convertible(const A&, B), ""); diff --git a/gcc/testsuite/g++.dg/ext/is_nothrow_convertible3.C b/gcc/testsuite/g++.dg/ext/is_nothrow_convertible3.C new file mode 100644 index 00000000000..05b1e1d9ad9 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/is_nothrow_convertible3.C @@ -0,0 +1,9 @@ +// PR c++/106784 +// { dg-do compile { target c++11 } } +// Make sure we don't reject this at runtime by trying to instantiate +// something that would be ill-formed. + +struct A; +struct B { template<class T> B(const T&) noexcept { T::nonexistent; } }; + +static_assert(__is_nothrow_convertible(const A&, B), ""); base-commit: 099a66498bf7a40764002793eba66c881a251b76 -- 2.37.3 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] c++: Instantiate less when evaluating __is_convertible 2022-09-26 16:25 ` [PATCH v2] " Marek Polacek @ 2022-09-26 16:41 ` Jason Merrill 0 siblings, 0 replies; 7+ messages in thread From: Jason Merrill @ 2022-09-26 16:41 UTC (permalink / raw) To: Marek Polacek, Patrick Palka; +Cc: GCC Patches, Jonathan Wakely On 9/26/22 12:25, Marek Polacek wrote: > On Mon, Sep 26, 2022 at 11:51:30AM -0400, Patrick Palka wrote: >> On Mon, 26 Sep 2022, Marek Polacek via Gcc-patches wrote: >> >>> Jon reported that evaluating __is_convertible in this test leads to >>> instantiating char_traits<char>::eq, which is invalid (because we >>> are trying to call a member function on a char) and so we fail to >>> compile the test. __is_convertible doesn't and shouldn't need to >>> instantiate so much, so let's limit it with a cp_unevaluated guard. >>> >>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? >>> >>> PR c++/106784 >>> >>> gcc/cp/ChangeLog: >>> >>> * method.cc (is_convertible): Use cp_unevaluated. >> >> I think is_nothrow_convertible would need cp_unevaluated too (or maybe we >> should define is_nothrow_convertible in terms of is_convertible). > > /facepalm, that's what I get by not using a single implementation for both! > >> And the testcase can probably be minimized to something like: >> >> struct A; >> struct B { template<class T> B(const T&) noexcept { T::nonexistent; } }; >> >> static_assert(__is_convertible(const A&, B)); >> static_assert(__is_nothrow_convertible(const A&, B)); > > Adjusted, thanks. > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? OK. > -- >8 -- > Jon reported that evaluating __is_convertible in a test led to > instantiating something ill-formed and so we failed to compile the test. > __is_convertible doesn't and shouldn't need to instantiate so much, so > let's limit it with a cp_unevaluated guard. Use a helper function to > implement both built-ins. > > PR c++/106784 > > gcc/cp/ChangeLog: > > * method.cc (is_convertible_helper): New. > (is_convertible): Use it. > (is_nothrow_convertible): Likewise. > > gcc/testsuite/ChangeLog: > > * g++.dg/ext/is_convertible3.C: New test. > * g++.dg/ext/is_nothrow_convertible3.C: New test. > --- > gcc/cp/method.cc | 23 ++++++++++++------- > gcc/testsuite/g++.dg/ext/is_convertible3.C | 9 ++++++++ > .../g++.dg/ext/is_nothrow_convertible3.C | 9 ++++++++ > 3 files changed, 33 insertions(+), 8 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/ext/is_convertible3.C > create mode 100644 gcc/testsuite/g++.dg/ext/is_nothrow_convertible3.C > > diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc > index c35a59fe56c..9f917f13134 100644 > --- a/gcc/cp/method.cc > +++ b/gcc/cp/method.cc > @@ -2236,6 +2236,19 @@ ref_xes_from_temporary (tree to, tree from, bool direct_init_p) > return ref_conv_binds_directly (to, val, direct_init_p).is_false (); > } > > +/* Worker for is_{,nothrow_}convertible. Attempt to perform an implicit > + conversion from FROM to TO and return the result. */ > + > +static tree > +is_convertible_helper (tree from, tree to) > +{ > + if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) > + return integer_one_node; > + cp_unevaluated u; > + tree expr = build_stub_object (from); > + return perform_implicit_conversion (to, expr, tf_none); > +} > + > /* Return true if FROM can be converted to TO using implicit conversions, > or both FROM and TO are possibly cv-qualified void. NB: This doesn't > implement the "Access checks are performed as if from a context unrelated > @@ -2244,10 +2257,7 @@ ref_xes_from_temporary (tree to, tree from, bool direct_init_p) > bool > is_convertible (tree from, tree to) > { > - if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) > - return true; > - tree expr = build_stub_object (from); > - expr = perform_implicit_conversion (to, expr, tf_none); > + tree expr = is_convertible_helper (from, to); > if (expr == error_mark_node) > return false; > return !!expr; > @@ -2258,10 +2268,7 @@ is_convertible (tree from, tree to) > bool > is_nothrow_convertible (tree from, tree to) > { > - if (VOID_TYPE_P (from) && VOID_TYPE_P (to)) > - return true; > - tree expr = build_stub_object (from); > - expr = perform_implicit_conversion (to, expr, tf_none); > + tree expr = is_convertible_helper (from, to); > if (expr == NULL_TREE || expr == error_mark_node) > return false; > return expr_noexcept_p (expr, tf_none); > diff --git a/gcc/testsuite/g++.dg/ext/is_convertible3.C b/gcc/testsuite/g++.dg/ext/is_convertible3.C > new file mode 100644 > index 00000000000..7a986d075c2 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/ext/is_convertible3.C > @@ -0,0 +1,9 @@ > +// PR c++/106784 > +// { dg-do compile { target c++11 } } > +// Make sure we don't reject this at runtime by trying to instantiate > +// something that would be ill-formed. > + > +struct A; > +struct B { template<class T> B(const T&) noexcept { T::nonexistent; } }; > + > +static_assert(__is_convertible(const A&, B), ""); > diff --git a/gcc/testsuite/g++.dg/ext/is_nothrow_convertible3.C b/gcc/testsuite/g++.dg/ext/is_nothrow_convertible3.C > new file mode 100644 > index 00000000000..05b1e1d9ad9 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/ext/is_nothrow_convertible3.C > @@ -0,0 +1,9 @@ > +// PR c++/106784 > +// { dg-do compile { target c++11 } } > +// Make sure we don't reject this at runtime by trying to instantiate > +// something that would be ill-formed. > + > +struct A; > +struct B { template<class T> B(const T&) noexcept { T::nonexistent; } }; > + > +static_assert(__is_nothrow_convertible(const A&, B), ""); > > base-commit: 099a66498bf7a40764002793eba66c881a251b76 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] c++: Instantiate less when evaluating __is_convertible 2022-09-26 15:22 [PATCH] c++: Instantiate less when evaluating __is_convertible Marek Polacek 2022-09-26 15:51 ` Patrick Palka @ 2022-09-26 16:02 ` Jonathan Wakely 2022-09-26 16:26 ` Marek Polacek 1 sibling, 1 reply; 7+ messages in thread From: Jonathan Wakely @ 2022-09-26 16:02 UTC (permalink / raw) To: Marek Polacek; +Cc: GCC Patches, Jason Merrill On Mon, 26 Sept 2022 at 16:23, Marek Polacek wrote: > > Jon reported that evaluating __is_convertible in this test leads to > instantiating char_traits<char>::eq, which is invalid (because we > are trying to call a member function on a char) N.B. in the original code wasn't trying to do something dumb like call a member function on a char, but it was using basic_string_view<X> where X is a class type without an operator== and so char_traits<X>::eq was invalid. I changed it to just use basic_string_view<char> and changed char_traits::eq to do something different, that was invalid for char. I can provide a less silly test case if you like, but I don't think it matters for the purposes of the testsuite. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] c++: Instantiate less when evaluating __is_convertible 2022-09-26 16:02 ` [PATCH] " Jonathan Wakely @ 2022-09-26 16:26 ` Marek Polacek 0 siblings, 0 replies; 7+ messages in thread From: Marek Polacek @ 2022-09-26 16:26 UTC (permalink / raw) To: Jonathan Wakely; +Cc: GCC Patches, Jason Merrill On Mon, Sep 26, 2022 at 05:02:36PM +0100, Jonathan Wakely wrote: > On Mon, 26 Sept 2022 at 16:23, Marek Polacek wrote: > > > > Jon reported that evaluating __is_convertible in this test leads to > > instantiating char_traits<char>::eq, which is invalid (because we > > are trying to call a member function on a char) > > N.B. in the original code wasn't trying to do something dumb like call > a member function on a char, but it was using basic_string_view<X> > where X is a class type without an operator== and so > char_traits<X>::eq was invalid. I changed it to just use > basic_string_view<char> and changed char_traits::eq to do something > different, that was invalid for char. Ack. > I can provide a less silly test case if you like, but I don't think it > matters for the purposes of the testsuite. I think no need to, I'm going to use Patrick's short test. Thanks, Marek ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2022-09-26 16:41 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-09-26 15:22 [PATCH] c++: Instantiate less when evaluating __is_convertible Marek Polacek 2022-09-26 15:51 ` Patrick Palka 2022-09-26 16:21 ` Jason Merrill 2022-09-26 16:25 ` [PATCH v2] " Marek Polacek 2022-09-26 16:41 ` Jason Merrill 2022-09-26 16:02 ` [PATCH] " Jonathan Wakely 2022-09-26 16:26 ` Marek Polacek
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