https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100472
Bug ID: 100472
Summary: [C++17] Wrong template non-type argument handling on
function reference to noexcept functions
Product: gcc
Version: 10.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: frankhb1989 at gmail dot com
Target Milestone: ---
Case:
template<void(&)()>
void h()
{}
void f() noexcept
{}
int main()
{
h<f>();
}
g++ prog.cc -Wall -Wextra -std=c++17
prog.cc: In function 'int main()':
prog.cc:10:7: error: no matching function for call to 'h<f>()'
10 | h<f>();
| ^
prog.cc:2:6: note: candidate: 'template<void (& <anonymous>)()> void h()'
2 | void h()
| ^
prog.cc:2:6: note: template argument deduction/substitution failed:
prog.cc:10:7: error: '(void (&)())f' is not a valid template argument for type
'void (&)()'
10 | h<f>();
| ^
prog.cc:10:7: note: it must be the name of a function with external linkage
Removing `noexcept` makes all errors disappeared. So, the real failure is from
the initialization of the template non-type parameter. This should not fail as
per the rules in [temp.arg.nontype], [dcl.init.ref] and [expr.const] (see also
N4268). Even if the conversion should have been failed, the last diagnostic
message is clearly wrong and confusing. This message comes from the conversion
performed on the template non-type argument as I see in
convert_nontype_argument_function in pt.c, and it should not occur since the
[temp.arg.nontype] changes in C++11.
