What are the characteristics of the “inline” keyword in C++?

The “inline” keyword in C++ is used to inline functions, so that the code of the function is inserted at the place where the function is called during compilation, rather than executing through a function call.

Here are the characteristics of the inline keyword:

1. Reduce function call overhead: by using inline functions, we can avoid the overhead of function calls, such as saving and restoring context, passing parameters, and so on.
2. Improving program execution speed: Since the code of inline functions is inserted at the call site, it can reduce the time of function calls and therefore enhance the program’s execution speed.
3. Decrease the size of the function body by copying the code of inline functions to the calling location, avoiding the overhead of saving and restoring the context during function calls and thus reducing the size of the function body.
4. Code bloat may occur as a result of inline functions, where the code is copied to every call site. If the code in the inline function is large or frequently called, it can lead to an increase in program size.
5. Inline functions are suitable for functions with short bodies, and may not bring much performance improvement for complex functions.

It is important to note that the “inline” keyword simply provides a suggestion to the compiler, and it is up to the compiler to decide whether to actually inline the function. Therefore, using “inline” does not guarantee that the function will be truly inlined.