Read Json from File

[llchris]

Hello, I am cynnad. I am loving so far your json library but i am encourring an issue with my code:

int read_json(const char* p_FilePath, json& p_Json) 
{
	std::ifstream stream;
	stream.open(p_FilePath);
	if(stream.is_open() && !stream.fail())
	{
		stream >> p_Json;
		return 0;
	}

	std::string errorMessage { "Failed to create an inputstream with the file in the path " };
	errorMessage.append(p_FilePath);
	__ERROR__(errorMessage);
	return 1;
}

Using the function:

          json myJsonConfig = {};
	  //Read from file and store into the json
	  if(!read_json("Test.json", myJsonConfig)) return -1;

This is what i came up after reading the wiki. This code seems not to work for me in fact i get a violation error :

Exception thrown at 0x00007FF797F6EF3B in Test.exe: 0xC0000005: access violation while reading the path 0x0000000000000050.

Did I read the json file correctly or did i misunderstand something? Thank you for reading.

[nlohmann]

Do you have a stacktrace?

Can you try this:

std::ifstream file("Test.json");
json j = json::parse(file);

[llchris]

Thank you for answering, I get the same error even using the parse method. I fugured out it is something related to atomic in _NODISCARD _Ty load(const memory_order _Order) const noexcept { // load with given memory order auto _As_bytes = _ISO_VOLATILE_LOAD32(_Storage); _Load_barrier(_Order); return reinterpret_cast<_Ty&>(_As_bytes); }

[nlohmann]

This sounds broken. Do you have a stack trace? Can you make sure you can read the file without the library?

[llchris]

Unfortunately I dont have a stack trace but I can provide this info:

| this | 0x0000000000000050 {_Storage={_Value=??? } } | const std::_Atomic_storage<int,4> *
  | _As_bytes | -858993460 | long
  | _Order | memory_order_relaxed (0) | std::memory_order

[nlohmann]

How do you know this is an issue in the library?

[llchris]

Honestly I don't know, I came here to understand if this was my problem or a library problem. Sometimes running this code even made my windows to reload with errors. If the file is inaccessible shouldnt the stream.is_open() return false and then print the error message?

[nlohmann]

Maybe. But code like

std::ifstream file("Test.json");
json j = json::parse(file);

has been executed millions of times without crashing a machine. As there is no exception, it seems that there is anything else very broken on the system. Can you try to run in debugger or with santizers?

[llchris]

Ok so now I tried to read from a different json and it worked but if i take it off the directory i still get the problem. So that error occures when the file is not reachable. My windows system is fine, that crash happened just on that code. I don't want to other users to possibly "crash windows" if the file is not in the directory so is there a way to prevent this? Thanks

[nlohmann]

If you try to read from a file that could not be opened, you should get an exception:

[json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literal

Can you do this with your file?

std::ifstream i("your_file");
std::stringstream ss;
ss << i.rdbuf();
std::cout << ss.str() << std::endl;

[llchris]

I get another violation access error of JSON_THROW(*static_cast<const detail::out_of_range*>(&ex)); using the file

[nlohmann]

With the stringstream code?

[llchris]

yea

[nlohmann]

That code does not involve the JSON library. Can you please execute it in isolation?