Failure to parse simple Json

[benstadin]

I'm a first time simdjson user. I understand the need for padding, yet I do get a weird error on every second or so build without any changes to code (which makes me believe it must have to do something with padding or similar) when I try to get the document as a object root via my getRootAsObject() method below.

Is there something obvious which I'm missing? Or is this indeed a bug?

Simdjson version is 3.1.7 from homebrew with Xcode 14.3 and Apple Clang, GNU++20.

The error I get is this:

Failed to get JSON document root as object: INCORRECT_TYPE: The JSON element does not have the requested type.

My code:

explicit JsonFile(const std::string &filename) {
        std::ifstream file(filename.c_str());
        if (!file.is_open()) {
            std::string what = "Failed to read JSON file: " + filename;
            throw MyException(what);
        }

        // Load the the file into a buffer
        std::string buffer;
        file.seekg(0, std::ios::end);
        // simdjson braucht padding: https://github.com/simdjson/simdjson/blob/master/doc/basics.md
        size_t size = size_t(file.tellg());
        buffer.resize(size);
        file.seekg(0, std::ios::beg);
        file.read(&buffer[0], file.tellg());
        
        // Store into padded json
        simdjson::padded_string json = buffer;
        simdjson::error_code error = _parser.iterate(json).get(_document);
        if (error != simdjson::SUCCESS) {
            std::string errStr = simdjson::error_message(error) ? std::string(simdjson::error_message(error)) : "";
            std::string what = "Failed to load json document: " + errStr;
            throw MyException(what);
        }
    }

    void getRootAsObject(simdjson::ondemand::object& result) {
        simdjson::error_code error = _document.get_object().get(result);
        if (error != simdjson::SUCCESS) {
            std::string errStr = simdjson::error_message(error) ? std::string(simdjson::error_message(error)) : "";
            std::string what = "Failed to get JSON document root as object: " + errStr;
            throw MyException(what);
        }
    }

[lemire]

You should be able to greatly simplify your code with a line such as...

json = padded_string::load(filename); 

Is there something obvious which I'm missing?

1. The file is read but never closed. You can fix that by using the line above...
2. After the JsonFile constructor, the simdjson::padded_string json instance which contains the input string is destroyed, and the memory is released. It is possible, just out of chance, that access to it might remain safe for a while, even after the destructor has been called (so your code might work some of the time), but it is certainly not safe and it will definitively crash some of the time. I refer you to our documentation which states that the input string must remain available during the parsing:

Please note that simdjson has been used in important production systems for many years. I am sure we still have bugs, and some are discovered from time to time, but the overwhelming majority of the library is bug-free at this point. We also benefit from extensive testing.