0.y.z build fails with gcc 6.3

[fedorov]

Errors:

/home/work/dcmqi/jsoncpp/jsoncpp.cpp:234:14: error: 'scoped_ptr' in namespace 'std' does not name a template type
 typedef std::scoped_ptr<CharReader> const  CharReaderPtr;
              ^~~~~~~~~~
/home/work/dcmqi/jsoncpp/jsoncpp.cpp: In function 'bool Json::parseFromStream(const Json::CharReader::Factory&, std::istream&, Json::Value*, std::__cxx11::string*)':
/home/work/dcmqi/jsoncpp/jsoncpp.cpp:2007:3: error: 'CharReaderPtr' was not declared in this scope
   CharReaderPtr const reader(fact.newCharReader());
   ^~~~~~~~~~~~~
/home/work/dcmqi/jsoncpp/jsoncpp.cpp:2008:10: error: 'reader' was not declared in this scope
   return reader->parse(begin, end, root, errs);
          ^~~~~~
/home/work/dcmqi/jsoncpp/jsoncpp.cpp: At global scope:
/home/work/dcmqi/jsoncpp/jsoncpp.cpp:3803:14: error: 'scoped_ptr' in namespace 'std' does not name a template type
 typedef std::scoped_ptr<StreamWriter> const  StreamWriterPtr;
              ^~~~~~~~~~
/home/work/dcmqi/jsoncpp/jsoncpp.cpp: In function 'std::__cxx11::string Json::writeString(const Json::StreamWriter::Factory&, const Json::Value&)':
/home/work/dcmqi/jsoncpp/jsoncpp.cpp:4924:3: error: 'StreamWriterPtr' was not declared in this scope
   StreamWriterPtr const writer(builder.newStreamWriter());
   ^~~~~~~~~~~~~~~
/home/work/dcmqi/jsoncpp/jsoncpp.cpp:4925:3: error: 'writer' was not declared in this scope
   writer->write(root, &sout);
   ^~~~~~
/home/work/dcmqi/jsoncpp/jsoncpp.cpp: In function 'std::ostream& Json::operator<<(std::ostream&, const Json::Value&)':
/home/work/dcmqi/jsoncpp/jsoncpp.cpp:4931:3: error: 'StreamWriterPtr' was not declared in this scope
   StreamWriterPtr const writer(builder.newStreamWriter());
   ^~~~~~~~~~~~~~~
/home/work/dcmqi/jsoncpp/jsoncpp.cpp:4932:3: error: 'writer' was not declared in this scope
   writer->write(root, &sout);
   ^~~~~~

[cdunn2001]

Old version? We do not use scoped_ptr:

  57 #if __cplusplus >= 201103L || (defined(_CPPLIB_VER) && _CPPLIB_VER >= 520)
  58 typedef std::unique_ptr<CharReader> CharReaderPtr;
  59 #else
  60 typedef std::auto_ptr<CharReader>   CharReaderPtr;
  61 #endif

[fedorov]

@cdunn2001 perhaps I am doing something wrong. What I did is I generated amalgamated header from the current 0.y.z branch, and the resulting jsoncpp.cpp clearly contains scoped_ptr, see https://github.com/fedorov/dcmqi/blob/update-jsoncpp/jsoncpp/jsoncpp.cpp#L233-L237. What am I missing?

[cdunn2001]

Well, yes, there was std::scoped_ptr on the old 0.y.z branch, but only for gcc>=6:

  57 #if __GNUC__ >= 6
  58 typedef std::scoped_ptr<StreamWriter> const  StreamWriterPtr;
  59 #else
  60 typedef std::auto_ptr<StreamWriter>          StreamWriterPtr;
  61 #endif

[cdunn2001]

Hmm. Maybe gcc 6.3 dropped std::scoped_ptr, or maybe you're building for C++11 (you could check the compilation flags actually used).

If you cannot find a work-around, the best solution is to switch to the master branch. Patches to 0.y.z are possible, but the whole purpose of that branch is to maintain compatibility with a variety of old compilers and systems. master is C++11 only (though it might currently still work with C++0x).

[fedorov]

We intentionally used 0.y.z to get rid of C++11 requirement. It's been working fine for our CI and most users (see CI banners on https://github.com/qiicr/dcmqi), but recently we got a report that it breaks with gcc 6.3. Looking here, it appears that the default mode in gcc 6 has been changed to -std=gnu++14, so perhaps this is the reason. I will experiment a bit more and report here.

[cdunn2001]

That's the difficulty of upgrading some things but not others.

However, if the only problem is scoped_ptr, we could back-port the change to unique_ptr.

[nolden]

With gcc 6 I successfully built recent master using -std=c++03, so I guess there is no C++11 code yet in jsoncpp?

[cdunn2001]

Yes, but that's the master branch. fedorov is using the 0.y.z branch, I think...

... Oh, I see. You're saying they could use master and simply set --std=c++03. Yes, for now that would work. We reserve the right to add C++11 features eventually, but you can always lock the version if that happens.

[Phibonacci]

I do not find anything about scoped_ptr ever being part of the STL. It is part of boost but I don't believe std::scoped_ptr ever compiled.

Checking the GCC version would be wrong anyway as it does not guarantee the program is compiled with the latest C++ version / ABI.

[Phibonacci]

Can you rollback this commit ?

#413

[Phibonacci]

I just realized the master version does not match the last release of the 0.x.y (0.10.6) which is using scoped_ptr. The tip of x.y.z is currently using std::unique_ptr<> with the macro JSON_HAS_UNIQUE_PTR which is never define.

Can you create a new release to avoid further confusion?

[cdunn2001]

A new release? We'll do that soon. But is master wrong?

We try not to touch the 0.y.z branch, since it is quite old.

[Phibonacci]

As stated in #828 0.x.y branch looks fine. A new release should fix this issue.

[cdunn2001]

A new "0.y.z" release, based on the tip of the 0.y.z branch?

[wanliqun]

Great for the new update here:
https://github.com/open-source-parsers/jsoncpp/releases/tag/0.10.7

I can even compile the project with gcc 8.2 now.