Re: [boost] [property_tree] Issue: erase is corrupting the tree

Subject: Re: [boost] [property_tree] Issue: erase is corrupting the tree
From: Seth (bugs_at_[hidden])
Date: 2017-06-09 02:39:34

On 06-06-17 10:32, Lukas via Boost wrote:
>     boost::property_tree::ptree loadedJSON;
>     boost::property_tree::read_json("animalList.json", loadedJSON);
>     auto assoc_it = loadedJSON.find("animals");
>     auto it = loadedJSON.to_iterator(assoc_it);
>     it = it->second.begin();
>     it++; // move to second item
>     loadedJSON.erase(it);
>     boost::property_tree::write_json("shorterList.json", loadedJSON);
You're using erase on the wrong container.

     auto it = loadedJSON.to_iterator(assoc_it);

Here, it points into the root ptree.

     it = it->second.begin();

Now, it points into the nested ptree ("animals")

    loadedJSON.erase(it);

That's undefined behaviour. Fix:

    #include <boost/property_tree/ptree.hpp>
    #include <boost/property_tree/json_parser.hpp>
    #include <iostream>

    using boost::property_tree::ptree;

    int main() {
        ptree loadedJSON;
        read_json("animalList.json", loadedJSON);

        //auto& animals = *loadedJSON.find("animals");
        auto& animals = loadedJSON.get_child("animals");

        auto it = animals.begin();
        it++; // move to second item
        animals.erase(it);

        write_json("shorterList.json", loadedJSON);
    }