Bug 721712 – dev-cpp/nlohmann_json-3.7.3: error: 'value' is not a member of 'std::is_constructible<nlohmann::basic_json<>, const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, long in

• Status: RESOLVED FIXED
• Product: Gentoo Linux

[Description Nicolas Werner 2020-05-08 22:52:53 UTC]

Compiling any application with gcc-10 using nlohmann_json fails, with an error like this (shortened, actual error is much longer):

/usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/include/g++-v10/bits/stl_uninitialized.h:137:72: Fehler: »value« ist kein Element von »std::is_constructible<nlohmann::basic_json<>, const nlohmann::basic_json<std::map, std::vector, std::__cxx11::basic_string<char, std::char_trai
ts<char>, std::allocator<char> >, bool, long int, long unsigned int, double, std::allocator, nlohmann::adl_serializer>&>«
  137 |       static_assert(is_constructible<_ValueType2, decltype(*__first)>::value,
      |  

This has been reported upstream already: https://github.com/nlohmann/json/issues/1920
And has been fixed in https://github.com/nlohmann/json/pull/2034

Adding the changes from that PR as a patch fixes any compilation issues. Since 3.8.0 is not released yet, I propose adding that patch for now to the 3.7.3 ebuild.

Reproducible: Always

Steps to Reproduce:
1.emerge nlohmann_json with the test useflag set
2.the tests should fail to compile. You can also test it with other applications using nlohmann_json, but this is the easiest way to test it.
3.
Actual Results:  
Compilation failures.

Expected Results:  
No compilation failures.

You can get the patch from this URL: https://patch-diff.githubusercontent.com/raw/nlohmann/json/pull/2034.patch

[Comment 1 Sam James 2020-05-08 22:55:59 UTC]

Can you file a PR to the gentoo repo?

[Comment 2 Nicolas Werner 2020-05-08 22:57:05 UTC]

Sure, will do.

[Comment 3 Nicolas Werner 2020-05-08 23:15:34 UTC]

I hope I did this correctly, I'm new to this: https://github.com/gentoo/gentoo/pull/15719

[Comment 4 Larry the Git Cow 2020-05-15 00:34:42 UTC]

The bug has been closed via the following commit(s):

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=29ae1e10e707b0d48cce53c08cf79ea3e26b07a8

commit 29ae1e10e707b0d48cce53c08cf79ea3e26b07a8
Author:     Nicolas Werner <[e-mail]>
AuthorDate: 2020-05-08 23:11:40 +0000
Commit:     Aaron Bauman <[e-mail]>
CommitDate: 2020-05-15 00:34:27 +0000

    dev-cpp/nlohmann_json: fix build with gcc-10
    
    Closes: https://bugs.gentoo.org/721712
    
    Signed-off-by: Nicolas Werner <[e-mail]>
    Closes: https://github.com/gentoo/gentoo/pull/15719
    Signed-off-by: Aaron Bauman <[e-mail]>

 .../files/nlohmann_json-3.7.3-gcc-10.patch         | 131 +++++++++++++++++++++
 dev-cpp/nlohmann_json/nlohmann_json-3.7.3.ebuild   |   4 +
 2 files changed, 135 insertions(+)