/Zc:__cplusplus leads to C2416 #1695

crusader-mike · 2019-07-31T22:46:54Z

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.

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

jaredgrubb · 2019-07-31T23:32:54Z

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

crusader-mike · 2019-07-31T23:44:47Z

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.

jaredgrubb · 2019-08-01T00:02:16Z

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 :)

stale · 2019-09-02T11:46:46Z

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.

crusader-mike · 2019-09-03T02:20:00Z

Bad bot!

t-b · 2019-09-03T15:03:54Z

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.

crusader-mike · 2019-09-04T00:12:04Z

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

stale · 2019-10-04T01:28:28Z

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.

mrstux · 2019-10-23T01:56:22Z

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.

nlohmann · 2019-10-23T05:48:24Z

This should be fixed on develop branch as it contains an updated version of Hedley. Can anyone try this?

t-b · 2019-10-23T12:13:26Z

I've added a PR which compiles with /Zc:__cplusplus. Let's see if that works now.

t-b · 2019-10-23T16:46:28Z

Fails in CI as well, see https://ci.appveyor.com/project/nlohmann/json/builds/28319126/job/qp8uvagt7i56g5bp.

@mrstux The best thing here is to fix the issue in https://github.com/nemequ/hedley, then incorporat the changes into the linked PR.

t-b · 2019-11-02T16:01:01Z

It's not about the definition. MSVC chokes on the friend. Using "__declspec(deprecated)" does not trigger the warning. see https://godbolt.org/z/lhPjC-.

stale · 2019-12-02T16:07:30Z

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.

t-b · 2020-02-27T15:59:12Z

@nlohmann Please reopen.

LanderlYoung · 2020-03-04T10:15:03Z

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.

t-b · 2020-03-18T08:24:04Z

@LanderlYoung The upstream bug in hedley was fixed.

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

dota17 · 2020-03-18T11:37:40Z

@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.

nlohmann · 2020-03-19T10:08:47Z

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 ?

t-b · 2020-03-19T12:00:19Z

@nlohmann Yeep, I've rebased #1958.

kenr · 2020-06-02T12:52:59Z

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.

nlohmann · 2020-06-03T19:29:42Z

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

kenr · 2020-06-04T06:25:52Z

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

nlohmann · 2020-06-04T08:18:07Z

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

This reverts commit ef90276. Because 3.7.3 does not build with MSVC 2017. See nlohmann/json#1695 for details.

…#7459)" This reverts commit 67dd3a8. Because 3.7.0 does not build with MSVC 2017. See nlohmann/json#1695 for details.

crusader-mike added the kind: bug label Jul 31, 2019

nlohmann added the platform: visual studio related to MSVC label Aug 3, 2019

stale bot added the state: stale the issue has not been updated in a while and will be closed automatically soon unless it is updated label Sep 2, 2019

stale bot removed the state: stale the issue has not been updated in a while and will be closed automatically soon unless it is updated label Sep 3, 2019

stale bot added the state: stale the issue has not been updated in a while and will be closed automatically soon unless it is updated label Oct 4, 2019

stale bot closed this as completed Oct 11, 2019

mrstux mentioned this issue Oct 23, 2019

Can #1695 be re-opened? #1808

Closed

nlohmann reopened this Oct 23, 2019

stale bot removed the state: stale the issue has not been updated in a while and will be closed automatically soon unless it is updated label Oct 23, 2019

t-b mentioned this issue Oct 23, 2019

appveyor.yml: Compile and test with latest version for __cplusplus macro on MSVC #1810

Closed

stale bot added the state: stale the issue has not been updated in a while and will be closed automatically soon unless it is updated label Dec 2, 2019

stale bot closed this as completed Dec 9, 2019

t-b mentioned this issue Jan 2, 2020

MSVC build failure with /Zc:__cplusplus and C++17 #1883

Closed

t-b mentioned this issue Feb 27, 2020

MSVC with /Zc:__cplusplus and deprecated on a friend function does not compile nemequ/hedley#33

Closed

nlohmann reopened this Feb 28, 2020

stale bot removed the state: stale the issue has not been updated in a while and will be closed automatically soon unless it is updated label Feb 28, 2020

t-b mentioned this issue Feb 28, 2020

appveyor.yml: Compile and test with latest version for __cplusplus ma… #1958

Merged

nlohmann closed this as completed in #1958 Apr 10, 2020

nlohmann added the solution: proposed fix a fix for the issue has been proposed and waits for confirmation label Apr 10, 2020

nlohmann self-assigned this Apr 10, 2020

nlohmann added this to the Release 3.7.4 milestone Apr 10, 2020

xyz1001 mentioned this issue Jun 1, 2020

Add nlohmann_json 3.4.0 for better compatibility conan-io/conan-center-index#1797

Merged

4 tasks

koprok pushed a commit to koprok/vcpkg that referenced this issue Jun 26, 2020

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

eb997e8

This reverts commit ef90276. Because 3.7.3 does not build with MSVC 2017. See nlohmann/json#1695 for details.

koprok pushed a commit to koprok/vcpkg that referenced this issue Jun 26, 2020

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

3143628

…#7459)" This reverts commit 67dd3a8. Because 3.7.0 does not build with MSVC 2017. See nlohmann/json#1695 for details.

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/Zc:__cplusplus leads to C2416 #1695

/Zc:__cplusplus leads to C2416 #1695

crusader-mike commented Jul 31, 2019

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/Zc:__cplusplus leads to C2416 #1695

/Zc:__cplusplus leads to C2416 #1695

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crusader-mike commented Jul 31, 2019

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