Question

Under what circumstances can you successfully return a pointer from a function?

Short answer

Answer: It is safe and correct to return a pointer from a function in C/C++ when the pointer is pointing to a global or static variable or to memory allocated on the heap with proper memory management. Avoid returning a pointer to a local variable, as this can result in undefined behavior due to invalid memory access.

Step-by-step solution

Understand the concept of pointers and functions

In C/C++, pointers are variables that store the address of another variable. We can use pointers to pass values, including arrays, from one function to another or to return values from a function. Returning a pointer from a function is an advanced concept and should be used carefully to avoid issues with memory management.

Returning a pointer to a local variable

Do not return a pointer to a local variable of the function. Local variables are allocated on the stack and are deallocated when the function returns. Consequently, the returned pointer points to an invalid memory location, which results in undefined behavior when accessed.

Returning a pointer to global or static variables

It is safe to return a pointer to a global or static variable since these variables have a lifetime throughout the program execution. They are not deallocated when the function returns, which guarantees a valid memory location even after the function call.

Returning a pointer to memory allocated on the heap

Allocating memory on the heap using "malloc" in C or "new" in C++ allows you to return a pointer to that memory location. However, it is crucial to manage memory allocation and deallocation correctly, avoiding memory leaks or access to invalid memory locations. Ensure that the allocated memory is deallocated after its use by the caller function. In conclusion, you can successfully return a pointer from a function under the following circumstances: 1. When pointing to a global or static variable. 2. When pointing to memory allocated on the heap, with proper memory management.