expansion pattern 'CompatibleObjectType' contains no argument packs, with CUDA 10

[carlosgalvezp]

Hi,

I'm using your JSON library in my code. I have a pretty old version (2.1) and would like to upgrade to 3.4.0. However the CUDA 10 compiler seems to have errors when trying to get data as a vectors. With the GCC compiler (5.4) it compiles fine.
I attach example code from this issue, where the issue was solved:

#include <iostream>

#include "json.hpp"

using nlohmann::json;

int main()
{
    auto j = R"(
    {
         "names": ["Tim", "Tom"],
         "num": [1.2, 2.3]
    }
    )"_json;

    std::vector<std::string> names = j["names"];

    for (auto i : names)
    {
        std::cout << i << " ";
    }

    // prints: Tim Tom 
}

This gives the following compilation errors:

$ nvcc -isystem include -std=c++14 main.cu 

include/json.hpp:552:151: error: expansion pattern 'CompatibleObjectType' contains no argument packs
include/json.hpp:552:154: error: template argument 4 is invalid
include/json.hpp:552:261: error: template argument 1 is invalid
include/json.hpp:552:263: error: template argument 3 is invalid
include/json.hpp:577:160: error: expansion pattern 'ConstructibleObjectType' contains no argument packs
include/json.hpp:577:163: error: template argument 4 is invalid
include/json.hpp:577:273: error: template argument 1 is invalid
include/json.hpp:577:275: error: template argument 3 is invalid
include/json.hpp:637:147: error: expansion pattern 'CompatibleArrayType' contains no argument packs
include/json.hpp:637:150: error: template argument 4 is invalid
include/json.hpp:637:335: error: template argument 1 is invalid
include/json.hpp:637:337: error: template argument 3 is invalid
include/json.hpp:667:244: error: expansion pattern 'ConstructibleArrayType' contains no argument packs
include/json.hpp:667:247: error: template argument 4 is invalid
include/json.hpp:667:81: error: parse error in template argument list
main.cu: In function 'int main()':
main.cu:16:118: error: conversion from 'nlohmann::basic_json<>::value_type {aka nlohmann::basic_json<>}' to non-scalar type 'std::vector<std::__cxx11::basic_string<char> >' requested

Using the get<std::vector<std::string>> method gives even more errors on top of the previous ones.

Have you seen this error before?

Thanks!

[nlohmann]

Thanks for reporting! I have not seen this before, but maybe someone has an idea.

[stale]

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.

[thoangtrvn]

I have the same issue with nvcc 10.0, compile with -std=c+=11

[cliffburdick]

Same issue with CUDA 10.1 with std=c++14

[kemalfidan]

Also running into this problem with CUDA 10.1 and c++ 11

[dean-shaff]

I've run into the same problem with CUDA 10.1, g++ 6.4.0, c++11.

[darrelpalke]

Having the same issue here. It's possible that this is related to a bug similar to this:
https://stackoverflow.com/questions/43380550/which-compiler-if-any-has-a-bug-in-parameter-pack-expansion

I'm not entirely sure what c compiler NVCC uses or if they have their own and have the same bug.

I was able to work around this issue by not putting any json.hpp code into .cu files. The project I'm working with uses VS to compile the cpp files and NVCC to compile the .cu files so perhaps this isn't feasible for everyone else.

I was also able to get around this by commenting out a lot of the vector/string code in the json.hpp header but then of course you can't read either data type, which wasn't workable for me.

[b-v]

I'm also have the same problem for the latest version, but it does work with CUDA 10.1 when I use version 3.2.0 of this JSON library (so newer than version 2.1 from the OP).

[nlohmann]

#1773 (comment)