"call to non-‘constexpr’ function" in bundled fmt

[limitedAtonement]

Here is an incomplete example that reproduces the problem:

#include "spdlog/spdlog.h"
std::shared_ptr<spdlog::logger> logger;
int main(int, char const **)
{
    std::string m{"{:06d}"};
    logger->info(m, 1);
    return 0;
}

I'm working against eb322062 (tag: v1.9.2) Bump version to 1.9.2 (and I was able to reproduce on 8826011c (origin/v1.x, v1.x) Merge pull request #2102 from yzz-ihep/v1.x). Invocation:

#!/bin/bash

set -ex;
g++ --version;
if [[ ! -d obj ]]; then mkdir obj; fi;
g++ -c -Wall -Wextra -pedantic -std=c++20 -O3 -DNDEBUG -MMD -Isrc/spdlog/include src/main.cpp -o obj/main.o;

The full output:

+ g++ --version
g++ (GCC) 11.1.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

+ [[ ! -d obj ]]
+ g++ -c -Wall -Wextra -pedantic -std=c++20 -O3 -DNDEBUG -MMD -Isrc/spdlog/include src/main.cpp -o obj/main.o
In file included from src/spdlog/include/spdlog/fmt/fmt.h:22,
                 from src/spdlog/include/spdlog/common.h:36,
                 from src/spdlog/include/spdlog/spdlog.h:12,
                 from src/main.cpp:1:
src/spdlog/include/spdlog/fmt/bundled/core.h: In function ‘int main(int, const char**)’:
src/main.cpp:6:17:   in ‘constexpr’ expansion of ‘fmt::v8::basic_format_string<char, int>(m)’
src/spdlog/include/spdlog/fmt/bundled/core.h:2835:51: error: ‘constexpr fmt::v8::basic_string_view<Char>::basic_string_view(const std::__cxx11::basic_string<Char, Traits, Alloc>&) [with Traits = std::char_traits<char>; Alloc = std::allocator<char>; Char = char]’ called in a constant expression
 2835 |   FMT_CONSTEVAL basic_format_string(const S& s) : str_(s) {
      |                                                   ^~~~~~~
src/spdlog/include/spdlog/fmt/bundled/core.h:470:17: note: ‘constexpr fmt::v8::basic_string_view<Char>::basic_string_view(const std::__cxx11::basic_string<Char, Traits, Alloc>&) [with Traits = std::char_traits<char>; Alloc = std::allocator<char>; Char = char]’ is not usable as a ‘constexpr’ function because:
  470 |   FMT_CONSTEXPR basic_string_view(
      |                 ^~~~~~~~~~~~~~~~~
src/spdlog/include/spdlog/fmt/bundled/core.h:472:21: error: call to non-‘constexpr’ function ‘const _CharT* std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::data() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’
  472 |       : data_(s.data()),
      |               ~~~~~~^~
In file included from /usr/include/c++/11.1.0/string:55,
                 from /usr/include/c++/11.1.0/stdexcept:39,
                 from /usr/include/c++/11.1.0/system_error:41,
                 from /usr/include/c++/11.1.0/bits/std_mutex.h:39,
                 from /usr/include/c++/11.1.0/bits/atomic_wait.h:49,
                 from /usr/include/c++/11.1.0/bits/atomic_base.h:41,
                 from /usr/include/c++/11.1.0/atomic:41,
                 from src/spdlog/include/spdlog/details/null_mutex.h:6,
                 from src/spdlog/include/spdlog/common.h:7,
                 from src/spdlog/include/spdlog/spdlog.h:12,
                 from src/main.cpp:1:
/usr/include/c++/11.1.0/bits/basic_string.h:2318:7: note: ‘const _CharT* std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::data() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ declared here
 2318 |       data() const _GLIBCXX_NOEXCEPT
      |       ^~~~

(which shows that the gcc version is 11.1.0 and compile flags include -Wall -Wextra -pedantic -std=c++20 -O3 -DNDEBUG -MMD).

This seems related maybe to #2023 except I'm not mixing format expression types? Maybe a relative of #1811?

[tt4g]

Related this issue: fmtlib/fmt#2455

[gabime]

fixed in fmt

[limitedAtonement]

Thank you! Which version of spdlog should contain this fix (so that the example above works)?

[gabime]

In the next release of spdlog version (no date yet)

Edit: probably after next fmt release with this fix.

[Brainfridge]

Is this fix out yet? I am seeing this in the compiled library in spdlog code I got today.

[iripiri]

I have the same issue, cloned spdlog today

[Kelvin-Ng]

I have the same issue on 1.12.0, but it works fine on 1.11.0.

[sammyj85]

It would seem this bug issue should be reopened. I also echo "I have the same issue on 1.12.0, but it works fine on 1.11.0."

Somewhere between Nov 2 2022 (1.11.0) and Feb 9 2023 it broke again.

[gabime]

@sammyj85 Can you try the v2.x branch? I hope it solves this.