What are the restriction in making a inline function?

Inline function is the optimization technique used by the compilers. One can simply prepend inline keyword to function prototype to make a function inline. Inline function instruct compiler to insert complete body of the function wherever that function got used in code. Advantages :- 1) It does not require function calling overhead. 2) It also save overhead of variables push/pop on the stack, while function calling. 3) It also save overhead of return call from a function. 4) It increases locality of reference by utilizing instruction cache. 5) After in-lining compiler can also apply intraprocedural optmization if specified. This is the most important one, in this way compiler can now focus on dead code elimination, can give more stress on branch prediction, induction variable elimination etc.. Disadvantages :- 1) May increase function size so that it may not fit on the cache, causing lots of cahce miss. 2) After in-lining function if variables number which are going to use register increases than they may create overhead on register variable resource utilization. 3) It may cause compilation overhead as if some body changes code inside inline function than all calling location will also be compiled. 4) If used in header file, it will make your header file size large and may also make it unreadable. 5) If somebody used too many inline function resultant in a larger code size than it may cause thrashing in memory. More and more number of page fault bringing down your program performance. 6) Its not useful for embeded system where large binary size is not preferred at all due to memory size constraints. read less

We put inline keyword in front of a function which requests a compiler to make that function as inline function. Following are the situations where inline functions may not work properly: 1.If we have two or three statements then it works otherwise compiler will ignore inline keyword and will treat as a normal function. 2.Functions returning values, having a loop, a switch or a go to statement. 3.If the function contains static variables. 4.If inline functions are recursive. read less