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libstdc++: Find make_error_code and make_error_condition via ADL only

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The new proposed resolution for LWG 3629 says that std::error_code and
std::error_condition should only use ADL to find their customization
points. This means we need to use a poison pill to prevent lookup from
finding overloads in the enclosing namespaces.

We can also remove the forward declarations of std::make_error_code and
std::make_error_condition, because they aren't needed now. ADL can find
them anyway (when std is an associated namespace), and unqualified name
lookup will not (and should not) find them.

libstdc++-v3/ChangeLog:

	* include/std/system_error (__adl_only::make_error_code): Add
	deleted function.
	(__adl_only::make_error_condition): Likewise.
	(error_code::error_code(ErrorCodeEnum)): Add using-declaration
	for deleted function.
	(error_condition::error_condition(ErrorConditionEnum)):
	Likewise.
	* testsuite/19_diagnostics/error_code/cons/lwg3629.cc: New test.
	* testsuite/19_diagnostics/error_condition/cons/lwg3629.cc: New test.
This commit is contained in:
Jonathan Wakely 2022-09-07 20:17:04 +01:00
parent 7a6564c9b2
commit d3883dc77b
3 changed files with 109 additions and 5 deletions
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18
libstdc++-v3/include/std/system_error
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@ -195,7 +195,11 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
* @{
*/
error_code make_error_code(errc) noexcept;
namespace __adl_only
{
void make_error_code() = delete;
void make_error_condition() = delete;
}
/** Class error_code
*
@ -231,7 +235,10 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
template<typename _ErrorCodeEnum,
typename = _Check<_ErrorCodeEnum>>
error_code(_ErrorCodeEnum __e) noexcept
{ *this = make_error_code(__e); }
{
using __adl_only::make_error_code;
*this = make_error_code(__e);
}
error_code(const error_code&) = default;
error_code& operator=(const error_code&) = default;
@ -330,8 +337,6 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
operator<<(basic_ostream<_CharT, _Traits>& __os, const error_code& __e)
{ return (__os << __e.category().name() << ':' << __e.value()); }
error_condition make_error_condition(errc) noexcept;
/** Class error_condition
*
* This class represents error conditions that may be visible at an API
@ -363,7 +368,10 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
template<typename _ErrorConditionEnum,
typename = _Check<_ErrorConditionEnum>>
error_condition(_ErrorConditionEnum __e) noexcept
{ *this = make_error_condition(__e); }
{
using __adl_only::make_error_condition;
*this = make_error_condition(__e);
}
error_condition(const error_condition&) = default;
error_condition& operator=(const error_condition&) = default;

48
libstdc++-v3/testsuite/19_diagnostics/error_code/cons/lwg3629.cc Normal file
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@ -0,0 +1,48 @@
// { dg-do compile { target c++11 } }
// 3629. make_error_code and make_error_condition are customization points
// Verify that make_error_code is looked up using ADL only.
namespace user
{
struct E1;
}
// N.B. not in associated namespace of E1, and declared before <system_error>.
user::E1 make_error_code(user::E1);
#include <future> // declares std::make_error_code(future_errc)
#include <system_error>
namespace user
{
struct E1
{
operator std::error_code() const;
};
struct E2
{
operator std::future_errc() const;
};
struct E3
{
operator std::errc() const;
};
}
template<> struct std::is_error_code_enum<user::E1> : std::true_type { };
template<> struct std::is_error_code_enum<user::E2> : std::true_type { };
template<> struct std::is_error_code_enum<user::E3> : std::true_type { };
// ::make_error_code(E1) should not be found by name lookup.
std::error_code e1( user::E1{} ); // { dg-error "here" }
// std::make_error_code(errc) should not be found by name lookup.
std::error_code e2( user::E2{} ); // { dg-error "here" }
// std::make_error_code(future_errc) should not be found by name lookup.
std::error_code e3( user::E3{} ); // { dg-error "here" }
// { dg-error "use of deleted function" "" { target *-*-* } 0 }

48
libstdc++-v3/testsuite/19_diagnostics/error_condition/cons/lwg3629.cc Normal file
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@ -0,0 +1,48 @@
// { dg-do compile { target c++11 } }
// 3629. make_error_code and make_error_condition are customization points
// Verify that make_error_condition is looked up using ADL only.
namespace user
{
struct E1;
}
// N.B. not in associated namespace of E1, and declared before <system_error>.
user::E1 make_error_condition(user::E1);
#include <future> // declares std::make_error_condition(future_errc)
#include <system_error>
namespace user
{
struct E1
{
operator std::error_code() const;
};
struct E2
{
operator std::future_errc() const;
};
struct E3
{
operator std::errc() const;
};
}
template<> struct std::is_error_condition_enum<user::E1> : std::true_type { };
template<> struct std::is_error_condition_enum<user::E2> : std::true_type { };
template<> struct std::is_error_condition_enum<user::E3> : std::true_type { };
// ::make_error_condition(E1) should not be found by name lookup.
std::error_condition e1( user::E1{} ); // { dg-error "here" }
// std::make_error_condition(errc) should not be found by name lookup.
std::error_condition e2( user::E2{} ); // { dg-error "here" }
// std::make_error_condition(future_errc) should not be found by name lookup.
std::error_condition e3( user::E3{} ); // { dg-error "here" }
// { dg-error "use of deleted function" "" { target *-*-* } 0 }