https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110143
Bug ID: 110143
Summary: std::format for pointer arguments does not work
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: bruno at clisp dot org
Target Milestone: ---
Created attachment 55272
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55272&action=edit
test case bug1.cc
The C++20 <format> facility (n4861.pdf section 20.20.2.2 paragraph 23 specifies
that pointers should be printable through std::format, either with no type
specifier, or with the type specifier 'p'.
Neither of these works with GCC 13.1.0.
How to reproduce:
Use the attached bug1.c and bug2.c files.
$ g++ -Wall -std=gnu++20 bug1.cc
In file included from bug1.cc:1:
/inst-gcc/13.1.0/include/c++/13.1.0/format: In instantiation of ‘class
std::__format::_Checking_scanner<char, int*>’:
/inst-gcc/13.1.0/include/c++/13.1.0/format:3642:4: required from ‘consteval
std::basic_format_string<_CharT, _Args>::basic_format_string(const _Tp&) [with
_Tp = char [4]; _CharT = char; _Args = {int*}]’
bug1.cc:11:27: required from here
/inst-gcc/13.1.0/include/c++/13.1.0/format:3564:10: error: static assertion
failed: std::formatter must be specialized for each type being formatted
3564 | (is_default_constructible_v<formatter<_Args, _CharT>> && ...),
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/inst-gcc/13.1.0/include/c++/13.1.0/format:3564:10: note:
‘std::is_default_constructible_v<std::formatter<int*, char> >’ evaluates to
false
/inst-gcc/13.1.0/include/c++/13.1.0/format: In instantiation of ‘constexpr void
std::__format::_Checking_scanner<_CharT,
_Args>::_M_parse_format_spec(std::size_t) [with _Tp = int*; _OtherArgs = {};
_CharT = char; _Args = {int*}; std::size_t = long unsigned int]’:
/inst-gcc/13.1.0/include/c++/13.1.0/format:3581:33: required from here
bug1.cc:11:27: in ‘constexpr’ expansion of ‘std::basic_format_string<char,
int*>("{:}")’
/inst-gcc/13.1.0/include/c++/13.1.0/format:3643:19: in ‘constexpr’ expansion
of ‘__scanner.std::__format::_Checking_scanner<char,
int*>::<anonymous>.std::__format::_Scanner<char>::_M_scan()’
/inst-gcc/13.1.0/include/c++/13.1.0/format:3453:30: in ‘constexpr’ expansion
of
‘((std::__format::_Scanner<char>*)this)->std::__format::_Scanner<char>::_M_on_replacement_field()’
/inst-gcc/13.1.0/include/c++/13.1.0/format:3505:15: in ‘constexpr’ expansion
of
‘((std::__format::_Scanner<char>*)this)->std::__format::_Scanner<char>::_M_format_arg(__id)’
/inst-gcc/13.1.0/include/c++/13.1.0/format:3594:38: error: use of deleted
function ‘std::formatter<_Tp, _CharT>::formatter() [with _Tp = int*; _CharT =
char]’
3594 | formatter<_Tp, _CharT> __f;
| ^~~
/inst-gcc/13.1.0/include/c++/13.1.0/format:140:7: note: declared here
140 | formatter() = delete; // No std::formatter specialization for
this type.
| ^~~~~~~~~
/inst-gcc/13.1.0/include/c++/13.1.0/format:3595:42: error: ‘struct
std::formatter<int*, char>’ has no member named ‘parse’
3595 | this->_M_pc.advance_to(__f.parse(this->_M_pc));
| ~~~~^~~~~
$ g++ -Wall -std=gnu++20 bug2.cc
In file included from bug2.cc:1:
/inst-gcc/13.1.0/include/c++/13.1.0/format: In instantiation of ‘class
std::__format::_Checking_scanner<char, int*>’:
/inst-gcc/13.1.0/include/c++/13.1.0/format:3642:4: required from ‘consteval
std::basic_format_string<_CharT, _Args>::basic_format_string(const _Tp&) [with
_Tp = char [5]; _CharT = char; _Args = {int*}]’
bug2.cc:11:27: required from here
/inst-gcc/13.1.0/include/c++/13.1.0/format:3564:10: error: static assertion
failed: std::formatter must be specialized for each type being formatted
3564 | (is_default_constructible_v<formatter<_Args, _CharT>> && ...),
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/inst-gcc/13.1.0/include/c++/13.1.0/format:3564:10: note:
‘std::is_default_constructible_v<std::formatter<int*, char> >’ evaluates to
false
/inst-gcc/13.1.0/include/c++/13.1.0/format: In instantiation of ‘constexpr void
std::__format::_Checking_scanner<_CharT,
_Args>::_M_parse_format_spec(std::size_t) [with _Tp = int*; _OtherArgs = {};
_CharT = char; _Args = {int*}; std::size_t = long unsigned int]’:
/inst-gcc/13.1.0/include/c++/13.1.0/format:3581:33: required from here
bug2.cc:11:27: in ‘constexpr’ expansion of ‘std::basic_format_string<char,
int*>("{:p}")’
/inst-gcc/13.1.0/include/c++/13.1.0/format:3643:19: in ‘constexpr’ expansion
of ‘__scanner.std::__format::_Checking_scanner<char,
int*>::<anonymous>.std::__format::_Scanner<char>::_M_scan()’
/inst-gcc/13.1.0/include/c++/13.1.0/format:3453:30: in ‘constexpr’ expansion
of
‘((std::__format::_Scanner<char>*)this)->std::__format::_Scanner<char>::_M_on_replacement_field()’
/inst-gcc/13.1.0/include/c++/13.1.0/format:3505:15: in ‘constexpr’ expansion
of
‘((std::__format::_Scanner<char>*)this)->std::__format::_Scanner<char>::_M_format_arg(__id)’
/inst-gcc/13.1.0/include/c++/13.1.0/format:3594:38: error: use of deleted
function ‘std::formatter<_Tp, _CharT>::formatter() [with _Tp = int*; _CharT =
char]’
3594 | formatter<_Tp, _CharT> __f;
| ^~~
/inst-gcc/13.1.0/include/c++/13.1.0/format:140:7: note: declared here
140 | formatter() = delete; // No std::formatter specialization for
this type.
| ^~~~~~~~~
/inst-gcc/13.1.0/include/c++/13.1.0/format:3595:42: error: ‘struct
std::formatter<int*, char>’ has no member named ‘parse’
3595 | this->_M_pc.advance_to(__f.parse(this->_M_pc));
| ~~~~^~~~~
