Skip to content

tests/unit-iterators2: use std::ranges::equals for range comparisons - #3950

Merged
nlohmann merged 1 commit into
nlohmann:developfrom
ArsenArsen:gcc13
Mar 5, 2023
Merged

nlohmann merged 1 commit into
nlohmann:developfrom
ArsenArsen:gcc13

Conversation

@ArsenArsen

Copy link
Copy Markdown
Contributor

This fixes a build error on GCC 13:

/home/arsen/nlohmann_json/tests/src/unit-iterators2.cpp: In function ‘void _DOCTEST_ANON_FUNC_2()’:
/home/arsen/nlohmann_json/tests/src/unit-iterators2.cpp:946:32: error: no match for ‘operator==’ (operand types are ‘doctest::detail::Expression_lhs<std::ranges::reverse_view<std::ranges::ref_view<nlohmann::json_abi_v3_11_2::basic_json<> > >&>’ and ‘nlohmann::json_abi_v3_11_2::json’ {aka ‘nlohmann::json_abi_v3_11_2::basic_json<>’})
946 | CHECK(reversed == j_expected);
| ^~ ~~~~~~~~~~
| |
| nlohmann::json_abi_v3_11_2::json {aka nlohmann::json_abi_v3_11_2::basic_json<>}

Bug: https://bugs.gentoo.org/895692
Closes: #3927

This PR also depends on trofis PR: #3895

Tested on x86_64-pc-linux-gnu in the default CMake configuration.

Pull request checklist

Read the Contribution Guidelines for detailed information.

  • Changes are described in the pull request, or an existing issue is referenced.
  • The test suite compiles and runs without error.
  • Code coverage is 100%. Test cases can be added by editing the test suite.
  • The source code is amalgamated; that is, after making changes to the sources in the include/nlohmann directory, run make amalgamate to create the single-header files single_include/nlohmann/json.hpp and single_include/nlohmann/json_fwd.hpp. The whole process is described here.

Please don't

  • The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
  • Specifically, I am aware of compilation problems with Microsoft Visual Studio (there even is an issue label for this kind of bug). I understand that even in 2016, complete C++11 support isn't there yet. But please also understand that I do not want to drop features or uglify the code just to make Microsoft's sub-standard compiler happy. The past has shown that there are ways to express the functionality such that the code compiles with the most recent MSVC - unfortunately, this is not the main objective of the project.
  • Please refrain from proposing changes that would break JSON conformance. If you propose a conformant extension of JSON to be supported by the library, please motivate this extension.
  • Please do not open pull requests that address multiple issues.

This fixes a build error on GCC 13:

  /home/arsen/nlohmann_json/tests/src/unit-iterators2.cpp: In function ‘void _DOCTEST_ANON_FUNC_2()’:
  /home/arsen/nlohmann_json/tests/src/unit-iterators2.cpp:946:32: error: no match for ‘operator==’ (operand types are ‘doctest::detail::Expression_lhs<std::ranges::reverse_view<std::ranges::ref_view<nlohmann::json_abi_v3_11_2::basic_json<> > >&>’ and ‘nlohmann::json_abi_v3_11_2::json’ {aka ‘nlohmann::json_abi_v3_11_2::basic_json<>’})
    946 |                 CHECK(reversed == j_expected);
        |                                ^~ ~~~~~~~~~~
        |                                   |
        |                                   nlohmann::json_abi_v3_11_2::json {aka nlohmann::json_abi_v3_11_2::basic_json<>}

Bug: https://bugs.gentoo.org/895692
Closes: nlohmann#3927
@coveralls

Copy link
Copy Markdown

Coverage Status

Coverage: 100.0%. Remained the same when pulling a49829b on ArsenArsen:gcc13 into b230614 on nlohmann:develop.

@nlohmann nlohmann left a comment

Copy link
Copy Markdown
Owner

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Looks good to me.

@nlohmann nlohmann added this to the Release 3.11.3 milestone Mar 5, 2023
@nlohmann
nlohmann merged commit 660d0b5 into nlohmann:develop Mar 5, 2023
@nlohmann

nlohmann commented Mar 5, 2023

Copy link
Copy Markdown
Owner

Thanks!

nlohmann added a commit that referenced this pull request Jul 9, 2026
…nthesis

Under C++20 P2468R2, a hand-written operator!= suppresses the compiler's
rewritten-candidate synthesis for operator==, preventing heterogeneous
comparisons like `std::string s; json j; s == j;` from compiling.

Fix by removing the hand-written operator!=, allowing the compiler to
synthesize != as !(a==b) in all language modes (C++20 member functions
and pre-C++20 friend functions).

Behavior change: operator!= now returns !(a==b) unconditionally, including
for special values like NaN and discarded. This means:
- NaN != NaN now returns true (matches IEEE-754 semantics)
- discarded != x now returns true for any x (matches !(discarded == x))

This also fixes underlying defects in previously-working code:
- Restores direct == comparison for views vs json (reverts std::ranges::equal
  workaround added in PR #3950 to dodge this bug)
- Re-enables std::string == json comparisons (uncomments check in
  unit-constructor1.cpp)

Fixes: #3868, #3979

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
nlohmann added a commit that referenced this pull request Jul 9, 2026
…nthesis (#5253)

* Fix #3868: Remove operator!= to enable P2468R2 rewritten candidate synthesis

Under C++20 P2468R2, a hand-written operator!= suppresses the compiler's
rewritten-candidate synthesis for operator==, preventing heterogeneous
comparisons like `std::string s; json j; s == j;` from compiling.

Fix by removing the hand-written operator!=, allowing the compiler to
synthesize != as !(a==b) in all language modes (C++20 member functions
and pre-C++20 friend functions).

Behavior change: operator!= now returns !(a==b) unconditionally, including
for special values like NaN and discarded. This means:
- NaN != NaN now returns true (matches IEEE-754 semantics)
- discarded != x now returns true for any x (matches !(discarded == x))

This also fixes underlying defects in previously-working code:
- Restores direct == comparison for views vs json (reverts std::ranges::equal
  workaround added in PR #3950 to dodge this bug)
- Re-enables std::string == json comparisons (uncomments check in
  unit-constructor1.cpp)

Fixes: #3868, #3979

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 🚨 fix warning

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
jwnimmer-tri pushed a commit to jwnimmer-tri/json that referenced this pull request Sep 21, 2026
…idate synthesis (nlohmann#5253)

* Fix nlohmann#3868: Remove operator!= to enable P2468R2 rewritten candidate synthesis

Under C++20 P2468R2, a hand-written operator!= suppresses the compiler's
rewritten-candidate synthesis for operator==, preventing heterogeneous
comparisons like `std::string s; json j; s == j;` from compiling.

Fix by removing the hand-written operator!=, allowing the compiler to
synthesize != as !(a==b) in all language modes (C++20 member functions
and pre-C++20 friend functions).

Behavior change: operator!= now returns !(a==b) unconditionally, including
for special values like NaN and discarded. This means:
- NaN != NaN now returns true (matches IEEE-754 semantics)
- discarded != x now returns true for any x (matches !(discarded == x))

This also fixes underlying defects in previously-working code:
- Restores direct == comparison for views vs json (reverts std::ranges::equal
  workaround added in PR nlohmann#3950 to dodge this bug)
- Re-enables std::string == json comparisons (uncomments check in
  unit-constructor1.cpp)

Fixes: nlohmann#3868, nlohmann#3979

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 🚨 fix warning

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Projects

None yet

Development

Successfully merging this pull request may close these issues.

GCC 13 build failures

3 participants

⌂ 换网址