What is the use case for a pointer to an array of unknown size?

Question

I recently realized that C ++ allows pointers to arrays of unknown sizes, like

int (*p)[]; 

The declaration above is not equivalent to int* p; . In fact, trying to use p to specify a fixed-size array results in a compile-time error, for example

 int data[42]; p = data; // error, cannot convert int [42] to int (*) [] 

or

 int* data; p = data; // error, cannot convert int * to int (*) [] 

My question is when and why should we use such a pointer to an array of unknown size? Are there any good reasons for this, and just use int* instead?

EDIT

Such objects are not allowed as function parameters, see Pointer to an array of undetermined size "(* p) []" is illegal in C ++, but legal in C , but can nevertheless be declared in the program.