The __forceinline keyword forces the compiler to compile a C or C++ function inline.

The semantics of __forceinline are exactly the same as those of the C++ inline keyword. The compiler attempts to inline a function qualified as __forceinline, regardless of its characteristics. However, the compiler does not inline a function if doing so causes problems. For example, a recursive function is inlined into itself only once.

__forceinline is a storage class qualifier. It does not affect the type of a function.

__forceinline static int max(int x, in y)
{
    return x > y ? x : y; // always inline if possible
}