7 Difference Between Inline Function And Normal Function In C++

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What Is An Inline Function?

The inline functions are a C++enhancement feature to increase the execution time of a program. In an inline function, a function call is directly replaced by an actual program code. It does not jump to any block because all the operations are performed inside the inline function. Compiler replaces the definition of inline functions at compile time instead of referring function definition at runtime.

Inline functions are mostly used for small computations. They are not suitable when large computing is involved. An inline function is similar to the normal function except that keyword inline is place before the function name. 

What You Need To Know About Inline Function

  • Inline function is a normal function which is defined by the keyword inline, it is a short function which is expanded by the compiler and its arguments are evaluated only once.
  • In inline function, the compiler replaces the function call with the function definition code and compiles the entire code. This process is referred to as expansion.
  • An inline function does not create function call overhead as the function definition code is replaced in the program.
  • Inline function in the repeated call such as in a loop wastes memory but saves CPU time to execute that call.
  • Using too many inline functions increases the executable file size because of the duplication of the same code.
  • All functions inside a class in C++ are implicitly inline.

 What Is A Normal Function?

A normal function is a reusable block of code that makes a program easier to understand, test and can easily modified without changing the calling program. Functions divide the code and modularize the program for better and effective results. In short, a larger program is divided into various subprograms which are called as functions.

When you divide a large program into various functions, it becomes easy to manage each function individually. Whenever an error occurs in the program, you can easily investigate faulty functions and correct only those errors. You can easily call and use functions whenever they are required which automatically leads in saving time and space.

What You Need To Know About Normal Function

  • A normal function is a reusable block of code that makes a program easier to understand, test and can easily modified without changing the calling program.
  • At the time of program execution, the code is compiled first and then afterwards converted to executable code.
  • The normal function creates overheads as and when a function call encounters.
  • Normal function in such calls does not waste memory but uses more CPU time to execute that call.
  • In normal functions which have small size of code, the time needed to make the function call’s jump is more than the time needed to execute the function’s code.
  • Using too many normal functions does not affect the file size after compilation.
  • All functions outside a class in C++ are normal functions.

Difference Between Inline Function And Normal Function In Tabular Form

BASIS OF COMPARISON INLINE FUNCTION NORMAL FUNCTION
Description Inline function is a normal function which is defined by the keyword inline, it is a short function which is expanded by the compiler and its arguments are evaluated only once.   A normal function is a reusable block of code that makes a program easier to understand, test and can easily modified without changing the calling program.  
Execution In inline function, the compiler replaces the function call with the function definition code and compiles the entire code. This process is referred to as expansion.   At the time of program execution, the code is compiled first and then afterwards converted to executable code.  
Overhead An inline function does not create function call overhead as the function definition code is replaced in the program.   The normal function creates overheads as and when a function call encounters.  
Memory Usage Inline function in the repeated call such as in a loop wastes memory but saves CPU time to execute that call.   Normal function in such calls does not waste memory but uses more CPU time to execute that call.  
Function Call Time In the inline function, no such case occurs. In normal functions which have small size of code, the time needed to make the function call’s jump is more than the time needed to execute the function’s code.  
Effect Of Too Many Inline Functions. Using too many inline functions increases the executable file size because of the duplication of the same code.   Using too many normal functions does not affect the file size after compilation.  
Function In Class All functions inside a class in C++ are implicitly inline.   All functions outside a class in C++ are normal functions.