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/Zc:__cplusplus leads to C2416 #1695

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#1958
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/Zc:__cplusplus leads to C2416#1695
#1958
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nlohmann
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kind: bugplatform: visual studiorelated to MSVCsolution: proposed fixa fix for the issue has been proposed and waits for confirmation
Milestone
Release 3.8.0

Description

@crusader-mike
crusader-mike
opened on Jul 31, 2019

OS: Windows 7
Compiler: MSVC 2017 (15.9.11)

If project uses /Zc:__cplusplus json lib v3.7.0 fails to compile with this:

C2416: attribute 'deprecated' cannot be applied in this context

Looks like MSVC doesn't like this attribute applied to operator>> definition.

Activity

  1. crusader-mike
    added
    kind: bug
    on Jul 31, 2019

  2. jaredgrubb commented on Jul 31, 2019

    @jaredgrubb
    jaredgrubb
    on Jul 31, 2019
    Contributor

    I don't see why there is any bug here. Can you explain why the deprecated attribute is not legal in that context?

  3. crusader-mike commented on Jul 31, 2019

    @crusader-mike
    crusader-mike
    on Jul 31, 2019
    Author

    I assume it complains because [[deprecated]] attribute was applied to definition. According to C++17 draft I have (10.6.4.p2):

    The attribute may be applied to the declaration of a class, a typedef-name, a variable, a non-static data member, a function, a namespace, an enumeration, an enumerator, or a template specialization.

    Looks like MS read it as "can't happen on a definition". I have no opinion about correctness of this position.

  4. jaredgrubb commented on Aug 1, 2019

    @jaredgrubb
    jaredgrubb
    on Aug 1, 2019
    Contributor

    Yeh, that's a nuance that I can't make a call on myself. Dumb fix would be just to disable C2416 for this file :)

  5. nlohmann
    added
    platform: visual studiorelated to MSVC
    on Aug 3, 2019

  6. stale commented on Sep 2, 2019

    @stale
    staleBot
    on Sep 2, 2019

    This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

  7. stale
    added
    state: stalethe issue has not been updated in a while and will be closed automatically soon unless it is updated
    on Sep 2, 2019

  8. crusader-mike commented on Sep 3, 2019

    @crusader-mike
    crusader-mike
    on Sep 3, 2019
    Author

    Bad bot!

  9. stale
    removed
    state: stalethe issue has not been updated in a while and will be closed automatically soon unless it is updated
    on Sep 3, 2019

  10. t-b commented on Sep 3, 2019

    @t-b
    t-b
    on Sep 3, 2019
    Contributor

    Not sure how the project rules here are with respect to selectively disabling warnings but why not propose a PR which uses pragma push/pop logic for MSVC to disable that warning for this piece of code? See https://stackoverflow.com/a/18463996 as a starting point.

  11. crusader-mike commented on Sep 4, 2019

    @crusader-mike
    crusader-mike
    on Sep 4, 2019
    Author

    or I could simply patch this lib in my vcpkg instance and avoid dealing with PR/etc ;)

  12. stale commented on Oct 4, 2019

    @stale
    staleBot
    on Oct 4, 2019

    This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

  13. stale
    added
    state: stalethe issue has not been updated in a while and will be closed automatically soon unless it is updated
    on Oct 4, 2019
  14. stale
    closed this as completedon Oct 11, 2019

  15. mrstux commented on Oct 23, 2019

    @mrstux
    mrstux
    on Oct 23, 2019

    I'm seeing this too.

    I tried disabling the warning via the push/pop mechanism, but it seems the compiler front-end doesn't understand that its a compiler warning, and the website doesn't document it either.

    In the end I added a check for MSVC to the deprecated language checks. Oh well.

    A bit hacky, but unblocking.

    /*
TODO: remove _MSC_VER when this is fixed.
https://github.com/nlohmann/json/issues/1695
*/
#if defined(__cplusplus) && (__cplusplus >= 201402L) && !defined(_MSC_VER)
    #define JSON_HEDLEY_DEPRECATED(since) JSON_HEDLEY_DIAGNOSTIC_DISABLE_CPP98_COMPAT_WRAP_([[deprecated("Since " #since)]])
    #define JSON_HEDLEY_DEPRECATED_FOR(since, replacement) JSON_HEDLEY_DIAGNOSTIC_DISABLE_CPP98_COMPAT_WRAP_([[deprecated("Since " #since "; use " #replacement)]])
#elif \

    And regarding closing this issue because its "stale", I guess its a novel approach to solving issues, just close them after 31 days.

  16. 12 remaining items

  17. LanderlYoung commented on Mar 4, 2020

    @LanderlYoung
    LanderlYoung
    on Mar 4, 2020

    Is there any progress here?

    As far as I know, the easy way is to disable the attribute for windows by:

    #if defined(__cplusplus) && (__cplusplus >= 201402L) && !defined(_MSC_VER)

    BTW: MSVC sucks on this and the __cplusplus Marco bug.

    Also, once MSVC fixed it, the last condition can be checking _MSC_VER range.

  18. t-b commented on Mar 18, 2020

    @t-b
    t-b
    on Mar 18, 2020
    Contributor

    @LanderlYoung The upstream bug in hedley was fixed.

    @nlohmann How do I upgrade to a newer hedley version?

  19. dota17 commented on Mar 18, 2020

    @dota17
    dota17
    on Mar 18, 2020
    Contributor

    @t-b
    I had compared the current version and the newest version of hedley.
    There are not a lot of differences or special changes. So it maybe ok to update the source codes.

  20. nlohmann commented on Mar 19, 2020

    @nlohmann
    nlohmann
    on Mar 19, 2020
    Owner

    I upgraded Hedley to version 13 in https://github.com/nlohmann/json/tree/feature/update_hedley - can someone check if this fixes this issue? @t-b ?

  21. t-b commented on Mar 19, 2020

    @t-b
    t-b
    on Mar 19, 2020
    Contributor

    @nlohmann Yeep, I've rebased #1958.

  22. nlohmann
    closed this as completedin #1958on Apr 10, 2020
  23. nlohmann
    added
    solution: proposed fixa fix for the issue has been proposed and waits for confirmation
    on Apr 10, 2020
  24. nlohmann
    self-assigned this
    on Apr 10, 2020
  25. nlohmann
    added this to the Release 3.7.4 milestone on Apr 10, 2020

  26. kenr commented on Jun 2, 2020

    @kenr
    kenr
    on Jun 2, 2020

    Is the 3.7.4/3.4.0 release with this fix planned anytime soon? I use bitsery with std::variant and that requires /Zc:__cplusplus for MSVC to set the correct __cplusplus value for C++17.

  27. nlohmann commented on Jun 3, 2020

    @nlohmann
    nlohmann
    on Jun 3, 2020
    Owner

    The next release will be version 3.8.0. I'm not sure how much more time I will need until it is ready.

  28. kenr commented on Jun 4, 2020

    @kenr
    kenr
    on Jun 4, 2020

    @nlohmann Is there anything I can help out with towards the 3.8.0 release?

  29. nlohmann commented on Jun 4, 2020

    @nlohmann
    nlohmann
    on Jun 4, 2020
    Owner

    Not really - but if you are using MSVC and want to help, you may want to have a look at #2117.

  30. koprok
    added 2 commits that reference this issue on Jun 26, 2020

    Refs microsoft#15: Revert "[nlohmann-json] Upgrade to 3.7.3"

    eb997e8

    Refs microsoft#15: Revert "[nlohmann-json] Update to 3.7.0 (microsoft…

    3143628
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