ms.date: "11/04/2016"

**Microsoft Specific**

The `__inline` keyword tells the compiler to substitute the code within the function definition for every instance of a function call. However, substitution occurs only at the compiler's discretion. For example, the compiler does not inline a function if its address is taken or if it is too large to inline.

For a function to be considered as a candidate for inlining, it must use the new-style function definition.

Use this form to specify an inline function:

`__inline` *type*opt*function-definition*`;`

The use of inline functions generates faster code and can sometimes generate smaller code than the equivalent function call generates for the following reasons:

- It saves the time required to execute function calls.

- Small inline functions, perhaps three lines or less, create less code than the equivalent function call because the compiler doesn't generate code to handle arguments and a return value.

- Functions generated inline are subject to code optimizations not available to normal functions because the compiler does not perform interprocedural optimizations.

Functions using `__inline` should not be confused with inline assembler code. See [Inline Assembler](../c-language/inline-assembler-c.md) for more information.

**END Microsoft Specific**

[inline, __inline, \__forceinline](../cpp/inline-functions-cpp.md)