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As we saw in the previous
video, function calls have a

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certain amount of overhead.

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We need to create an activation
record, push it on the stack,

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deal with parameters, pop off the
activation record when the function

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terminates and deal with the
return addresses and return values.

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Although all of this can
happen very quickly and

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efficiently, it still happens.

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Sometimes we have a very simple
function and the function call

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overhead might be greater than the
time spent executing the function.

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In cases such as these, we
can suggest to the compiler

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that it generate inline code.

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Inline code is basically inline
assembly code that avoids

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the function call overhead.

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Inline code is generally faster.

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But if you inline a function many
times, then you're duplicating

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function code in many places and
it could lead to larger binaries.

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That said, compilers are
so sophisticated now that

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they'll likely inline code
even without your suggestion.

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Let's see what an inline
function looks like.

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Here you can see the syntax
for an inline function.

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We simply precede the function
return type with the keyword inline.

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Inline functions are usually declared
in header or .h files since the

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definition must be available to
every source file that uses it.

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As mentioned earlier, compilers
are so good now that most will

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make short functions like this
inline anyway even if you don't

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provide the inline keyword.

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Don't worry too much about asking
the compiler to inline your

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functions, but now you know what
inline functions are in case you

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see them in c++ code out there.