What is the function of the “inline” keyword in C++?

In C++, the purpose of the inline keyword is to inform the compiler to expand the code inside the function body at the call site, in order to reduce the overhead of function calls and improve program efficiency.

When a function is modified with the ‘inline’ keyword, the compiler will attempt to insert the code of the function directly at the calling location instead of executing it through a function call. This can help avoid the overhead of generating stack frames, passing parameters, and handling return values during function calls, ultimately improving the efficiency of the program.

It is important to note that the “inline” keyword is just a suggestion to the compiler, and the compiler may choose to ignore this suggestion. Generally, the compiler will decide whether to expand a function as inline code based on factors such as the complexity of the function and how frequently it is called. Additionally, inline functions are typically defined in header files so that the compiler can see the definition in every file and perform inline expansion.