What will happen if you do not use a return statement in a function?

When a function in C++ does not have a return statement, the behavior depends on the function's return type. If the function is defined to return an integer type and lacks a return statement, it will not return any meaningful value, which can lead to undefined behavior. However, if the function is explicitly defined with a return type of void, it means that the function is not expected to return a value at all, making the absence of a return statement appropriate.

In the case of functions defined with an integer return type, C++ may allow the function to implicitly return a value of zero if it reaches the end of the function body without a return statement. This implicit behavior effectively acts as a default return of zero, though it's important to note that this can lead to subtle bugs, as the returned value is not the one specified by the programmer.

Understanding the difference between the return types and how they behave when a return statement is omitted is critical for writing robust and predictable code.