Declaring symbols as json_weak shouldn't be mandatory.

[xvln]

It's pretty strange that this library defines all the weak symbols that it does. I can't think of a good reason for it, and I can think of many downsides... ideally there would be a way to turn that off, at the very least.

[sheredom]

Have you got a usecase where this affects you?

It's there so that it works as a single header (the alternative being doing what STB libs do and have a single C file you need to define an implementation macro in).