xeus, nlohmann-json: error: an attribute list cannot appear here

[ryandesign (Ryan Carsten Schmidt)]

​xeus does not build:

/opt/local/include/nlohmann/json.hpp:22424:5: error: an attribute list cannot appear here
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, parse(ptr, ptr + len))
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/local/include/nlohmann/json.hpp:1066:110: note: expanded from macro 'JSON_HEDLEY_DEPRECATED_FOR'
    #define JSON_HEDLEY_DEPRECATED_FOR(since, replacement) JSON_HEDLEY_DIAGNOSTIC_DISABLE_CPP98_COMPAT_WRAP_([[deprecated("Since " #since "; use " #replacement)]])
                                                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/local/include/nlohmann/json.hpp:819:5: note: expanded from macro 'JSON_HEDLEY_DIAGNOSTIC_DISABLE_CPP98_COMPAT_WRAP_'
    xpr \
    ^

[Schamschula (Marius Schamschula)]

Yosemite? I have no way of testing any potential fixes for this, other than throwing things at the build bot.

[ryandesign (Ryan Carsten Schmidt)]

Yes, Yosemite.

You can see from the ​xeus port page that it built fine on 10.7-10.9 using newer MacPorts clang.

It failed on 10.10 using Apple clang 7 and failed on 10.11 using Apple clang 8.

It built fine on 10.13 using Apple clang 9.

10.12 is busy and hasn't built this yet.

But a good guess might be to blacklist {clang < 900}, if we want to solve it by blacklisting.

Although xeus is the port that failed to build, the file generating the error is from nlohmann-json. Maybe that indicates that the fix should be in nlohmann-json.

Maybe the problem should be reported to the upstream developers so that they have a chance to weigh in on a fix.

[Schamschula (Marius Schamschula)]

In f7071707a9c1b6f3893abf5caf36c37f3cfdbc28/macports-ports (master):

xeus: attempt to fix error: an attribute list cannot appear here

See: #60765

[ryandesign (Ryan Carsten Schmidt)]

Thanks.