error: ‘BasicJsonType’ in namespace ‘::’ does not name a type

[simulationcloud]

I get this error when compiling with nvcc, which is using g++6.4.1. I am specifying the --std=c++11 flag.

The version of nlohmann/json is 3.1.2.

Any help would be greatly appreciated!

[nlohmann]

Could you indicate the line where the error occurs or paste the complete error message here? What was the code you tried to compile?

[simulationcloud]

/home/ec2-user/dev/john/Flow360_3.26.2018/json/include/nlohmann/detail/iterators/iter_impl.hpp:46:11: error:
This is the error I get by only including the header file #include "nlohmann/json.hpp":

‘BasicJsonType’ in namespace ‘::’ does not name a type
friend BasicJsonType;
^~~~~~~~~~~~~

I reverted to version 2.1.2 and got it to compile, but I would like to use the latest version.

[theodelrieu]

Seems like a compiler bug to me...

Could you try patching the iter_impl.hpp?

using J = BasicJsonType;
friend J;

[simulationcloud]

hmm. Same thing with the patch:
/home/ec2-user/dev/john/Flow360_3.26.2018/json/include/nlohmann/detail/iterators/iter_impl.hpp:48:11: error: ‘BasicJsonType’ in namespace ‘::’ does not name a type
friend J;

[theodelrieu]

This is weird, I guess it's the same problem if you change the name of the template parameter directly?

[simulationcloud]

I think it's a bug with nvcc. If I move the function to a separate cpp file and compile it only with gcc, it works.

[nlohmann]

Thanks for reporting back!

[schwarzschild-radius]

is there anyway to make it work with nvcc?

[schwarzschild-radius]

This answer in Stackoverflow solves the problem. Adding a wrapper around the BasicJsonType works with nvcc and gcc.

template<typename T>
struct BasicJsonType_wrapper{
    typedef T type;
};

template<typename BasicJsonType>
class iter_impl
{
    /// allow basic_json to access private members
    friend iter_impl<typename std::conditional<std::is_const<BasicJsonType>::value, typename     std::remove_const<BasicJsonType>::type, const BasicJsonType>::type>;
    // friend BasicJsonType;
    friend class BasicJsonType_wrapper<BasicJsonType>::type;
    friend iteration_proxy<iter_impl>;