Can't use nlohmann on Linux

[TomyFrank]

Description

I've cloned the repo and tried to use it in a simple C++ app but it produces an error.

Reproduction steps

After cloning the repo, moved the json folder in my project directory then included json.hpp it got the error:

 fatal error: nlohmann/detail/json_custom_base_class.hpp: No such file or directory
   49 | #include <nlohmann/detail/json_custom_base_class.hpp>

Expected vs. actual results

I expected the string {"happy": true,"pi": 3.141} on Terminal

Minimal code example

#include <iostream>
#include <string>
#include "json/include/nlohmann/json.hpp"

  int main() {
      auto j = R"(
     {
      "happy": true,
      "pi": 3.141
     }
    )"_json;
    auto data = j.dump();
    std::cout << data << '\n';
    return 0;
}

Error messages

fatal error: nlohmann/detail/json_custom_base_class.hpp: No such file or directory
   49 | #include <nlohmann/detail/json_custom_base_class.hpp

Compiler and operating system

Linux GCC

Library version

version 3

Validation

• [ ] The bug also occurs if the latest version from the develop branch is used.
• [ ] I can successfully compile and run the unit tests.

[nlohmann]

You need to properly configure the library search path to the json/include folder and then use #include <nlohmann/json.hpp>.

[TomyFrank]

You have said it's a header-only library. so inclduing that would be enough useually but it's not. How to properly configure the library search path to the json/include?

[nlohmann]

You did not use the single header version which is in the single_include folder. Otherwise, follow https://github.com/nlohmann/json?tab=readme-ov-file#integration.

[TomyFrank]

The single_include folder doesn't exist in the repo folder so I downloaded both json and json_fwd headers in the project directory and changed the code:

#include <iostream>
#include "json.hpp"
#include "json_fwd.hpp"

  int main() {
      auto j = R"(
     {
      "happy": true,
      "pi": 3.141
     }
    )"_json;
    auto data = j.dump();
    std::cout << data << '\n';
    return 0;
}

Error:

 json.hpp:34:10: fatal error: nlohmann/adl_serializer.hpp: No such file or directory
   34 | #include <nlohmann/adl_serializer.hpp>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

[nlohmann]

• You wrote that you cloned the repo, so there should be a single_include folder. Please check.
• If you want to use the files in the include folder, then just including json.hpp or json_fwd.hpp (don't include both, you probably only need json.hpp), then you must set your include path.

[TomyFrank]

Downloaded the ZIP and inslcued json.hpp and it runs. Thanks. So the easiest way to use nlohmann-json is this way yeah?

[nlohmann]

Good that you managed it.