build failure on upcoming gcc-12: test/src/unit-regression1.cpp:392:22: error: ambiguous overload for 'operator=' #3138

trofi · 2021-11-13T11:48:22Z

On gcc-12 (20211107 snapshot) std::string amended it's constructors to a form that fails regression tests building:

mkdir b && cd b
cmake ..
make
...
[ 71%] Building CXX object test/CMakeFiles/test-regression1.dir/src/unit-regression1.cpp.o
/home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp: In function 'void _DOCTEST_ANON_FUNC_2()':
/home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:392:22: error: ambiguous overload for 'operator=' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'nlohmann::basic_json<>::value_type' {aka 'nlohmann::basic_json<>'})
  392 |         s2 = o["name"];
      |                      ^
In file included from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/string:53,
                 from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/locale_classes.h:40,
                 from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/locale:39,
                 from /home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:33:
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:627:21: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::nullptr_t) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::nullptr_t = std::nullptr_t]' (deleted)
  627 |       basic_string& operator=(nullptr_t) = delete;
      |                     ^~~~~~~~
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:682:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  682 |       operator=(const basic_string& __str)
      |       ^~~~~~~~
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:720:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  720 |       operator=(basic_string&& __str)
      |       ^~~~~~~~
In file included from /home/slyfox/dev/git/nlohmann-json/test/thirdparty/doctest/doctest_compatibility.h:6,
                 from /home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:30:
/home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:398:37: error: ambiguous overload for 'operator=' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'nlohmann::basic_json<>::value_type' {aka 'nlohmann::basic_json<>'})
  398 |         CHECK_THROWS_AS(s2 = o["int"], json::type_error);
      |                                     ^
/home/slyfox/dev/git/nlohmann-json/test/thirdparty/doctest/doctest.h:1844:23: note: in definition of macro 'DOCTEST_CAST_TO_VOID'
 1844 |     static_cast<void>(__VA_ARGS__);                                                                \
      |                       ^~~~~~~~~~~
/home/slyfox/dev/git/nlohmann-json/test/thirdparty/doctest/doctest.h:2163:44: note: in expansion of macro 'DOCTEST_ASSERT_THROWS_AS'
 2163 | #define DOCTEST_CHECK_THROWS_AS(expr, ...) DOCTEST_ASSERT_THROWS_AS(expr, DT_CHECK_THROWS_AS, "", __VA_ARGS__)
      |                                            ^~~~~~~~~~~~~~~~~~~~~~~~
/home/slyfox/dev/git/nlohmann-json/test/thirdparty/doctest/doctest.h:2576:36: note: in expansion of macro 'DOCTEST_CHECK_THROWS_AS'
 2576 | #define CHECK_THROWS_AS(expr, ...) DOCTEST_CHECK_THROWS_AS(expr, __VA_ARGS__)
      |                                    ^~~~~~~~~~~~~~~~~~~~~~~
/home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:398:9: note: in expansion of macro 'CHECK_THROWS_AS'
  398 |         CHECK_THROWS_AS(s2 = o["int"], json::type_error);
      |         ^~~~~~~~~~~~~~~
In file included from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/string:53,
                 from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/locale_classes.h:40,
                 from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/locale:39,
                 from /home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:33:
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:627:21: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::nullptr_t) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::nullptr_t = std::nullptr_t]' (deleted)
  627 |       basic_string& operator=(nullptr_t) = delete;
      |                     ^~~~~~~~
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:682:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  682 |       operator=(const basic_string& __str)
      |       ^~~~~~~~
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:720:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  720 |       operator=(basic_string&& __str)
      |       ^~~~~~~~
In file included from /home/slyfox/dev/git/nlohmann-json/test/thirdparty/doctest/doctest_compatibility.h:6,
                 from /home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:30:
/home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:402:39: error: ambiguous overload for 'operator=' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'nlohmann::basic_json<>::value_type' {aka 'nlohmann::basic_json<>'})
  402 |         CHECK_THROWS_WITH(s2 = o["int"], "[json.exception.type_error.302] type must be string, but is number");
      |                                       ^
/home/slyfox/dev/git/nlohmann-json/test/thirdparty/doctest/doctest.h:1844:23: note: in definition of macro 'DOCTEST_CAST_TO_VOID'
 1844 |     static_cast<void>(__VA_ARGS__);                                                                \
      |                       ^~~~~~~~~~~
/home/slyfox/dev/git/nlohmann-json/test/thirdparty/doctest/doctest.h:2167:46: note: in expansion of macro 'DOCTEST_ASSERT_THROWS_WITH'
 2167 | #define DOCTEST_CHECK_THROWS_WITH(expr, ...) DOCTEST_ASSERT_THROWS_WITH(expr, #expr, DT_CHECK_THROWS_WITH, __VA_ARGS__)
      |                                              ^~~~~~~~~~~~~~~~~~~~~~~~~~
/home/slyfox/dev/git/nlohmann-json/test/thirdparty/doctest/doctest.h:2577:38: note: in expansion of macro 'DOCTEST_CHECK_THROWS_WITH'
 2577 | #define CHECK_THROWS_WITH(expr, ...) DOCTEST_CHECK_THROWS_WITH(expr, __VA_ARGS__)
      |                                      ^~~~~~~~~~~~~~~~~~~~~~~~~
/home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:402:9: note: in expansion of macro 'CHECK_THROWS_WITH'
  402 |         CHECK_THROWS_WITH(s2 = o["int"], "[json.exception.type_error.302] type must be string, but is number");
      |         ^~~~~~~~~~~~~~~~~
In file included from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/string:53,
                 from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/locale_classes.h:40,
                 from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/locale:39,
                 from /home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:33:
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:627:21: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::nullptr_t) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::nullptr_t = std::nullptr_t]' (deleted)
  627 |       basic_string& operator=(nullptr_t) = delete;
      |                     ^~~~~~~~
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:682:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  682 |       operator=(const basic_string& __str)
      |       ^~~~~~~~
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:720:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  720 |       operator=(basic_string&& __str)
      |       ^~~~~~~~
/home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:1174:16: error: ambiguous overload for 'operator=' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'nlohmann::json' {aka 'nlohmann::basic_json<>'})
 1174 |         test = v;
      |                ^
In file included from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/string:53,
                 from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/locale_classes.h:40,
                 from /nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/locale:39,
                 from /home/slyfox/dev/git/nlohmann-json/test/src/unit-regression1.cpp:33:
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:627:21: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::nullptr_t) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::nullptr_t = std::nullptr_t]' (deleted)
  627 |       basic_string& operator=(nullptr_t) = delete;
      |                     ^~~~~~~~
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:682:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  682 |       operator=(const basic_string& __str)
      |       ^~~~~~~~
/nix/store/0hvbmcf38gqpr6c49h7zl3iy228afaz0-gcc-12.0.0/include/c++/12.0.0/bits/basic_string.h:720:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  720 |       operator=(basic_string&& __str)
      |       ^~~~~~~~
make[2]: *** [test/CMakeFiles/test-regression1.dir/build.make:76: test/CMakeFiles/test-regression1.dir/src/unit-regression1.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:2148: test/CMakeFiles/test-regression1.dir/all] Error 2
make: *** [Makefile:146: all] Error 2

Which compiler and operating system are you using?

Compiler: gcc-12 development snapshot
Operating system: x86_64-linux

Which version of the library did you use?

the develop branch

The text was updated successfully, but these errors were encountered:

nlohmann · 2021-11-20T17:40:06Z

I would like to test this in the CI - can you tell me how I can get a development snapshot of GCC, preferably for Ubuntu?

trofi · 2021-11-20T21:43:54Z

Oh, that's a good question. Looking around ubuntu has https://launchpad.net/ubuntu/+source/gcc-snapshot. Looking at impish release latest release there is 20210827. It does not yet have a std::string change added on Oct 1 in https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=cf876562c592193732f869e9f96034a42d0fad89 . I hope it eventually catches up.

From superficial test in VM it's enough to install it as:

$ apt install gcc-snapshot
$ export PATH=/usr/lib/gcc-snapshot/bin:$PATH
$ cmake ...

I personally build gcc locally from https://ftp.mpi-inf.mpg.de/mirrors/gnu/mirror/gcc.gnu.org/pub/gcc/snapshots/LATEST-12/ (Current is from Oct 14).

nlohmann · 2021-11-21T10:04:45Z

Thanks, I was not aware of package gcc-snapshot.

nlohmann · 2021-11-21T12:14:26Z

I can reproduce the issue with gcc-latest (GCC) 12.0.0 20211114 (experimental).

nlohmann · 2021-11-21T12:31:50Z

The failing regression tests are for #144 and #464.

nlohmann · 2021-12-29T19:32:52Z

Same error occurred again in #3226

musicinmybrain · 2022-01-15T15:25:41Z

GCC 12 is now in Fedora Rawhide, if that helps with testing.

(I found this bug because it’s causing https://github.com/monocasual/giada builds to fail in Fedora Rawhide.)

xvitaly · 2022-01-16T11:23:27Z

I can confirm. All dependent packages are now FTBFS.

nlohmann · 2022-01-16T11:24:51Z

That's too bad. I have not yet understood the reason for the error, let alone whether it's a bug in the library and how to fix it.

jwakely · 2022-01-17T10:03:04Z

https://jwakely.github.io/pkg-gcc-latest/ has GCC snapshots packages for Ubuntu, Fedora, RHEL/CentOS and Tumbleweed.

The error is due to GCC 12 implementing P2166R1 "Prohibit std::basic_string and std::basic_string_view construction from nullptr", which is required by the C++23 draft. I made the change apply unconditionally to older standards too, because assigning nullptr to a basic_string was always undefined behaviour anyway. Apparently it changes the overload set for your library, causing an error during overload resolution.

nlohmann · 2022-01-18T12:25:15Z

As described in https://en.cppreference.com/w/cpp/23, we will have the same problem with Clang libc++ 13 and MSVC STL 19.30. What I have not understood is whether deleting basic_string(nullptr_t) is actually meant to also affect C++11/C++14/C++17 builds.

t-b · 2022-01-18T14:24:22Z

What I have not understood is whether deleting basic_string(nullptr_t) is actually meant to also affect C++11/C++14/C++17 builds.

I have found https://www.kitware.com/itk-informs-c-stl-development/ a while ago and from that I would say this is only deleted in C++23 builds. See also microsoft/STL#1995 (comment) from linked from there.

jwakely · 2022-01-18T15:48:22Z

The deleted basic_string(nullptr) constructor is new in C++23, but constructing a std::string from nullptr was always undefined behaviour, so I made it present unconditionally for C++11/14/17/20 in GCC's std::lib. I can't understand what the conversions on your code are supposed to be doing, so I can't tell whether your code was always doing something bad and it's only being diagnosed now, or if the new constructor changes the behaviour of correct code.

Could you give a simplified example of what conversion is supposed to happen when constructing a std::string from a basic_json<>?

jwakely · 2022-01-18T15:55:38Z

I think this is probably an approximation of what you're doing, right?

#include <string>

struct S
{
  operator const char*() const { return ""; }
  operator std::nullptr_t() const { return {}; }
};

std::string s{ S{} };

This is valid in C++20 and earlier, but ill-formed in C++23. And it demonstrates that the change should be limited to C++23. I'll change GCC.

jwakely · 2022-01-18T16:00:03Z

Filed as a GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104099

t-b · 2022-01-18T16:07:08Z

I've compiled latest gcc-trunk locally here g++ (GCC) 12.0.1 20220118 (experimental) and with the following patch

diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 92308c557..8fd2b357f 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -19043,6 +19043,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     template < typename ValueType, typename std::enable_if <
                    detail::conjunction <
                        detail::negation<std::is_pointer<ValueType>>,
+                       detail::negation<std::is_same<ValueType, nullptr_t>>,
                        detail::negation<std::is_same<ValueType, detail::json_ref<basic_json>>>,
                                         detail::negation<std::is_same<ValueType, typename string_t::value_type>>,
                                         detail::negation<detail::is_basic_json<ValueType>>,

it compiles and all tests pass. The fix goes in the same direction as #3138 (comment). It would have helped me if I read the reply first before trying to fix it ;)

EDIT:
As explanation the above diff is from

json/include/nlohmann/json.hpp

Lines 1870 to 1890 in 293f67f

    
               @since version 1.0.0 
        
               */ 
        
               template < typename ValueType, typename std::enable_if < 
        
                              detail::conjunction < 
        
                                  detail::negation<std::is_pointer<ValueType>>, 
        
                                  detail::negation<std::is_same<ValueType, detail::json_ref<basic_json>>>, 
        
                                                   detail::negation<std::is_same<ValueType, typename string_t::value_type>>, 
        
                                                   detail::negation<detail::is_basic_json<ValueType>>, 
        
                                                   detail::negation<std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>>, 
        
           #if defined(JSON_HAS_CPP_17) && (defined(__GNUC__) || (defined(_MSC_VER) && _MSC_VER >= 1910 && _MSC_VER <= 1914)) 
        
                                                           detail::negation<std::is_same<ValueType, std::string_view>>, 
        
           #endif 
        
                                                           detail::is_detected_lazy<detail::get_template_function, const basic_json_t&, ValueType> 
        
                                                           >::value, int >::type = 0 > 
        
                                                   JSON_EXPLICIT operator ValueType() const 
        
               { 
        
                   // delegate the call to get<>() const 
        
                   return get<ValueType>(); 
        
               }

and handles implicit conversion. I don't see a reason why we would like to convert to nullptr_t here.

nlohmann · 2022-01-19T20:15:54Z

Thanks @t-b for the fix! I tried it, and it worked for GCC 12. Unfortunately, it does not work for any other compiler :-/

See #3226.

The error is

/__w/json/json/single_include/nlohmann/json.hpp:19046:65: error: template argument for template type parameter must be a type
                       detail::negation<std::is_same<ValueType, nullptr_t>>,
                                                                ^~~~~~~~~

Any idea?

gregmarr · 2022-01-19T20:39:49Z

Should be std::nullptr_t

nlohmann · 2022-01-19T20:44:44Z

Good catch! Totally overlooked that. :-/

t-b · 2022-01-19T21:19:11Z

Jeep std:: is missing, hacked it a bit too fast ;)

nlohmann · 2022-01-22T12:12:55Z

The code compiles, but there is one test failing when compiling the code with C++20:

TEST CASE:  lexicographical comparison operators
  values
  comparison: less

/__w/json/json/test/src/unit-comparison.cpp:213: ERROR: CHECK( (j_values[i] < j_values[j]) == expected[i][j] ) is NOT correct!
  values: CHECK( false == 1 )
  logged: i := 12
          j := 13
          j_values[i] := [1,2,3]
          j_values[j] := ["one","two","three"]

/__w/json/json/test/src/unit-comparison.cpp:213: ERROR: CHECK( (j_values[i] < j_values[j]) == expected[i][j] ) is NOT correct!
  values: CHECK( true == 0 )
  logged: i := 13
          j := 12
          j_values[i] := ["one","two","three"]
          j_values[j] := [1,2,3]

The same test succeeds with Clang (Linux, macOS) in C++20 mode. Any ideas?

gregmarr · 2022-01-25T17:33:31Z

Looks like a change in how the default comparisons are happening in C++20 with the new generated comparisons. Looking at this in Compiler Explorer to see if I can track it down.

gregmarr · 2022-01-28T20:55:11Z

Confirmed different behavior of comparing std::vector<nlohmann::json<>> between -std=c++17 and -std=c++20 in GCC trunk.

The former calls std::operator<(vector<json>const&,vector<json>const&) and the latter calls std::operator<=>(vector<json>const&,vector<json>const&) so there is some difference in implementation there.

nlohmann · 2022-01-30T12:10:41Z

Would it make sense to implement operator<=> for basic_json instead of the usual operators when compiled for C++20?

jwakely · 2022-01-30T12:33:14Z

If you have implicit conversions then yes, you should provide your own <=>. Otherwise std::lib components that want to use <=> will do so via your implicit conversions, with possibly unexpected results.

gregmarr · 2022-02-03T17:23:50Z

I dug into that and still couldn't get it to pass. It would be good to replace all the comparison and equality operators with <=> for both the main class and the type enum, but it won't necessarily fix this issue.

falbrechtskirchinger · 2022-03-04T19:42:39Z

I dug into that and still couldn't get it to pass. It would be good to replace all the comparison and equality operators with <=> for both the main class and the type enum, but it won't necessarily fix this issue.

Worse than "won't necessarily fix this issue", libcxx [1] doesn't fully implement three way comparison for various std types yet, creating more problems. I've tried.

So, we'll have to solve/work around the underlying issue using the existing operators first, then optionally add the spaceship operator and guard that with requires clauses to work around missing standard library support.

Guess I know how I'll spend the weekend. 😉

[1] https://libcxx.llvm.org/Status/Spaceship.html

* 🔧 use proper GCC binary * 🔧 add more GCC warning flags * ⚗️ try fix from #3138 (comment) * Fix custom allocator test build failures (C++20) Allocator tests fail to compile in C++20 mode with clang+MS STL due to missing copy constructors. * Fix test build failures due to missing noexcept (gcc-12) * alt_string has multiple member functions that should be marked noexcept. * nlohmann::ordered_map constructors can be noexcept. Compilation failures result from the warning flag -Werror=noexcept and gcc-12. * Disable broken comparison tests in C++20 mode Co-authored-by: Niels Lohmann <mail@nlohmann.me>

trofi added the kind: bug label Nov 13, 2021

nlohmann added the confirmed label Nov 21, 2021

nlohmann added the state: help needed the issue needs help to proceed label Nov 21, 2021

nlohmann mentioned this issue Nov 21, 2021

Help needed #3112

Open

nlohmann mentioned this issue Dec 29, 2021

Add more GCC warning flags #3226

Closed

nlohmann added a commit that referenced this issue Jan 19, 2022

⚗️ try fix from #3138 (comment)

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nlohmann added a commit that referenced this issue Jan 19, 2022

⚗️ try fix from #3138 (comment)

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gregmarr mentioned this issue Feb 3, 2022

Tests failing when compiling with c++20 #3207

Closed

falbrechtskirchinger pushed a commit to falbrechtskirchinger/json that referenced this issue Mar 4, 2022

⚗️ try fix from nlohmann#3138 (comment)

dd93f8c

falbrechtskirchinger pushed a commit to falbrechtskirchinger/json that referenced this issue Mar 4, 2022

⚗️ try fix from nlohmann#3138 (comment)

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falbrechtskirchinger pushed a commit to falbrechtskirchinger/json that referenced this issue Mar 5, 2022

⚗️ try fix from nlohmann#3138 (comment)

d7f181b

falbrechtskirchinger mentioned this issue Mar 6, 2022

Fix C++20/gcc-12 issues (Part 1) #3379

Merged

falbrechtskirchinger pushed a commit to falbrechtskirchinger/json that referenced this issue Mar 6, 2022

⚗️ try fix from nlohmann#3138 (comment)

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falbrechtskirchinger pushed a commit to falbrechtskirchinger/json that referenced this issue Mar 6, 2022

⚗️ try fix from nlohmann#3138 (comment)

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falbrechtskirchinger pushed a commit to falbrechtskirchinger/json that referenced this issue Mar 6, 2022

⚗️ try fix from nlohmann#3138 (comment)

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nlohmann added solution: proposed fix a fix for the issue has been proposed and waits for confirmation and removed state: help needed the issue needs help to proceed labels Mar 7, 2022

nlohmann self-assigned this Mar 7, 2022

nlohmann added this to the Release 3.10.6 milestone Mar 7, 2022

nlohmann closed this as completed in #3379 Mar 7, 2022

nlohmann added the release item: 🐛 bug fix label Mar 7, 2022

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build failure on upcoming gcc-12: test/src/unit-regression1.cpp:392:22: error: ambiguous overload for 'operator=' #3138

build failure on upcoming gcc-12: test/src/unit-regression1.cpp:392:22: error: ambiguous overload for 'operator=' #3138

trofi commented Nov 13, 2021

nlohmann commented Nov 20, 2021

trofi commented Nov 20, 2021

nlohmann commented Nov 21, 2021

nlohmann commented Nov 21, 2021

nlohmann commented Nov 21, 2021

nlohmann commented Dec 29, 2021

musicinmybrain commented Jan 15, 2022

xvitaly commented Jan 16, 2022

nlohmann commented Jan 16, 2022

jwakely commented Jan 17, 2022

nlohmann commented Jan 18, 2022

t-b commented Jan 18, 2022

jwakely commented Jan 18, 2022

jwakely commented Jan 18, 2022

jwakely commented Jan 18, 2022

t-b commented Jan 18, 2022 •

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nlohmann commented Jan 19, 2022

gregmarr commented Jan 19, 2022

nlohmann commented Jan 19, 2022

t-b commented Jan 19, 2022

nlohmann commented Jan 22, 2022

gregmarr commented Jan 25, 2022

gregmarr commented Jan 28, 2022 •

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nlohmann commented Jan 30, 2022

jwakely commented Jan 30, 2022

gregmarr commented Feb 3, 2022

falbrechtskirchinger commented Mar 4, 2022

build failure on upcoming gcc-12: test/src/unit-regression1.cpp:392:22: error: ambiguous overload for 'operator=' #3138

build failure on upcoming gcc-12: test/src/unit-regression1.cpp:392:22: error: ambiguous overload for 'operator=' #3138

Comments

trofi commented Nov 13, 2021

Which compiler and operating system are you using?

Which version of the library did you use?

nlohmann commented Nov 20, 2021

trofi commented Nov 20, 2021

nlohmann commented Nov 21, 2021

nlohmann commented Nov 21, 2021

nlohmann commented Nov 21, 2021

nlohmann commented Dec 29, 2021

musicinmybrain commented Jan 15, 2022

xvitaly commented Jan 16, 2022

nlohmann commented Jan 16, 2022

jwakely commented Jan 17, 2022

nlohmann commented Jan 18, 2022

t-b commented Jan 18, 2022

jwakely commented Jan 18, 2022

jwakely commented Jan 18, 2022

jwakely commented Jan 18, 2022

t-b commented Jan 18, 2022 • edited Loading

nlohmann commented Jan 19, 2022

gregmarr commented Jan 19, 2022

nlohmann commented Jan 19, 2022

t-b commented Jan 19, 2022

nlohmann commented Jan 22, 2022

gregmarr commented Jan 25, 2022

gregmarr commented Jan 28, 2022 • edited Loading

nlohmann commented Jan 30, 2022

jwakely commented Jan 30, 2022

gregmarr commented Feb 3, 2022

falbrechtskirchinger commented Mar 4, 2022

t-b commented Jan 18, 2022 •

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gregmarr commented Jan 28, 2022 •

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