You could tag dynamically allocated objects with some magic bytes. To then check whether a string is dynamically allocated, you can simply compare the first few

You could tag dynamically allocated objects with some magic bytes. To then check whether a string is dynamically allocated, you can simply compare the first few bytes against the magic bytes. This is a probabilistic method, but if you use enough magic bytes, it becomes basically impossible to go wrong. See e.g. https://github.com/99991/dynamic/blob/a423a04061ee44bad0720fbd29f2321cc276564a/src/dynamic_gc.c#L21 https://github.com/99991/dynamic/blob/a423a04061ee44bad0720f... for an example (incidentally also a C JSON parser, but with automatic garbage collection).