merge_with and arena usage

[KimBP]

I'm trying to use rapidYaml to parse a settings file required by my application.
Basically the structure is like this:

ryml::Tree tree; // Global tree containing my settings

set_factory_default();
get_from_settings_file():

In set_factory_default I build my full settings tree with default values.
In get_from_settings_file() I open the settings file and parse it into a local (stack variable) tree.

ryml::Tree filetree = ryml::parse_in_place(ryml::to_substr(filedata));
tree.merge_with(&filetree);

When I return from get_from_settings_file() tree is updated with 'overrides' from my filedata. Unfortunately the first key-val pair read from filedata is corrupted. I think it is due to the substr and/or filetree object being destroyed when returning (i.e. stack is reused for other stuff)
I've found one solution (which I do consider a none solution)

Make filetree global too and use
filetree = ryml::parse_in_arena(ryml::to_csubstr(filedata);

Isn't there a way to ensure data follows the tree I'm merging into?

[biojppm]

(Sorry for the late reply, Github's notifications are just broken for me).

Indeed, any data added to tree needs to go on existing for as long as tree does. In this case you are adding from filedata, so you need to make sure that it exists with tree. There are several ways, but one simple way is to do filedata = tree.alloc_arena(filesize) on the destination tree, then still do the parse in place into the temporary filetree.

ryml::Tree tree;
set_factory_default();

{
    size_t filesize = ...;
    ryml::substr filedata = tree.alloc_arena(filesize); // place the filedata in the destination tree
    file_get_contents(file, filedata);
    ryml::Tree filetree = ryml::parse_in_place(filedata); // read the temp tree in place
    tree.merge_with(&filetree);
}

// at this point, filetree's contents are safely in the final tree.

For a similar example, see this note.

HTH.

[biojppm]

Also, you may want to take a look at c4conf, which does exactly what you are looking for.