Segmentation fault when a JSON string with whitespaces is passed to boost::json::parse() function

[Elnee]

Segmentation fault when a JSON string with whitespaces is passed to boost::json::parse() function

[sdkrystian]

@Elnee Per [class.temporary] p4, temporary objects are destroyed after evaluating the full-expression in which they appear (which in this case is the initialization of object). When a temporary object is bound to a reference, its lifetime will be extended to that of the reference if, and only if, one of the conditions specified by [class.temporary] p6 are met. Binding a reference to the result of calling a non-static member function of a temporary object does not satisfy any of these conditions, so the lifetime is not extended.

[grisumbras]

json::parse returns a json::value, which you don't store anywhere. You instead get a reference to its subobject of type json::object. At the end of that statement the value goes out of scope and destroys its internal object. After that you use a dangling reference. In order to fix this you should store either the value or the object:

const auto value = boost::json::parse(json);
const auto& object = value.as_object();
// or
const auto object = boost::json::parse(json).as_object();

[Elnee]

@sdkrystian Many thanks for the detailed explanation.

[Elnee]

@grisumbras Thank you, it works. But I don't understand why using a const-ref doesn't expand the lifetime of that object.
As I see boost::json::value has a union returned by as_object(). Is it because its lifetime is bound to the instance of boost::json::value?

[Elnee]

And also, isn't it a bit misleading that I should think about as_object() method in such a way? I thought about it as getting the same object but in a different representation (due to the as prefix). It turned out to return some internals to me.

Doesn't it force me to know some internal library implementation details aside from the interface as a user?