https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96489
Bug ID: 96489
Summary: Three way comparison operator failure to synthesize
traditional comparitors
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
User-defined <=> doesn't generate == or != though user-defined operator== and
operator<=> = default do.
/usr/local/opt/gcc/bin/g++-10 -std=c++20 foo.cc && ./a.out
foo.cc: In function 'int main()':
foo.cc:21:9: error: no match for 'operator!=' (operand types are 'foo' and
'foo')
21 | if (a != b) std::cout << "not ";
| ~ ^~ ~
| | |
| foo foo
foo.cc:25:11: error: no match for 'operator==' (operand types are 'foo' and
'foo')
25 | if (!(a == c)) std::cout << "not ";
| ~ ^~ ~
| | |
| foo foo
#include <iostream>
struct foo {
int content;
foo(int x) : content { x } {}
// works: auto operator <=> (foo const& rhs) const = default;
// works: auto operator == (foo const& rhs) const { return content ==
rhs.content; }
// fails:
auto operator <=> (foo const& rhs) const { return content <=>
rhs.content; }
};
int main() {
foo a { 1 };
foo b { 2 };
foo c { 1 };
if (a != b) std::cout << "not ";
std::cout << "equal" << std::endl;
if (!(a == c)) std::cout << "not ";
std::cout << "equal" << std::endl;
return 0;
Result:
/usr/local/opt/gcc/bin/g++-10 -std=c++20 foo.cc && ./a.out
foo.cc: In function 'int main()':
foo.cc:21:9: error: no match for 'operator!=' (operand types are 'foo' and
'foo')
21 | if (a != b) std::cout << "not ";
| ~ ^~ ~
| | |
| foo foo
foo.cc:25:11: error: no match for 'operator==' (operand types are 'foo' and
'foo')
25 | if (!(a == c)) std::cout << "not ";
| ~ ^~ ~
| | |
| foo foo
