Checking if a pointer is allocated memory or not

Question

Can we check whether a pointer passed to a function is allocated with memory or not in C?

I have wriiten my own function in C which accepts a character pointer -

Answer 1

No, in general there is no way to do this.

Furthermore, if your interface is just "pass a pointer to a buffer where I will put stuff", then the caller may choose not to allocate memory at all, and instead use a fixed size buffer that's statically allocated or an automatic variable or something. Or perhaps it's a pointer into a portion of a larger object on the heap.

If your interface specifically says "pass a pointer to allocated memory (because I'm going to deallocate it)", then you should expect that the caller will do so. Failure to do so isn't something you can reliably detect.