An int will be 32 bits on any non-ancient platform, so this means, for each of those lines:
- a JSON file with nested values exceeding 2 billion depth
- a file with more than 2 billion lines
- a line with more than 2 billion characters
- a JSON file with nested values exceeding 2 billion depth
- a file with more than 2 billion lines
- a line with more than 2 billion characters
If you are nesting 2 Billion times in a row ( at minimum this means repeat { 2 billion times followed by a value before } another 2 billion times. You have messed up.
You have 4GB of "padding"...at minimum.
You file is going to be Petabytes in size for this to make any sense.
You are using a terrible format for whatever you are doing.
You are going to need a completely custom parser because nothing will fit in memory. I don't care how much RAM you have.
Simply accessing an element means traversing a nested object 2 billion times in probably any parser in the world is going to take somewhere between minutes and weeks per access.
All that is going to happen in this program is a crash.
I appreciate that people want to have some pointless if(depth > 0) check everywhere, but if your depth is anywhere north of million in any real world program, something messed up a long long time ago, never mind waiting until it hits 2 billion.
An after the fact check would be the wrong way to deal with UB, you'd need to check for < INT_MAX before the increment in order to avoid it.
Restricting the input to a reasonable size is an easy workaround for sure, but this limitation isn't indicated everywhere, so anyone deciding to consume this random project into their important code wouldn't know to defend against such situation.
In a web server scenario, 2GiB of { (which would trigger two overflows) in a compressed request would require a couple hundred kilobytes to two megabytes, depending on how old your server software is.
And in the spirit of your profile text I'm quite glad for such landmines being out there to trip up those that do blindly ingest all code they can find.
Maybe more importantly, I won’t trust the rest of the code if the author doesn’t seem to have the finite range of integer types in mind.