Can you explain what is meant by 'inline function' in programming?

An inline function is a function that the compiler attempts to replace directly at the call site, instead of a normal call through the stack. This can help avoid the overhead of a function call (such as transition and context saving), which can improve performance.

For example, in C++, you can declare a function with the inline keyword:

inline int sum(int a, int b) {
    return a + b;
}

When compiled, calls to sum(2, 3) will be replaced directly with 2 + 3.

However, excessive use of inline functions can increase the size of the final code (code bloat), so compilers usually decide on inlining on their own, considering the complexity of the function.