Meaning of __inout_opt given before function parameter

Question

What is the meaning of the keyword given below, when it is given before any function parameter ?

__inout_opt

Thanks

I looked online, [this msdn article](https://msdn.microsoft.com/en-us/library/windows/desktop/aa383701(v=vs.85).aspx) was the third hit. — StoryTeller - Unslander Monica, Jan 17 '18 at 13:27
Can you give an example of where it's used? Also note that symbols starting with double underscore are reserved (and private) for the compiler and standard library. — Some programmer dude, Jan 17 '18 at 13:28

score 0 · Accepted Answer · answered Jan 17 '18 at 13:31

0

It's a header annotation in the Windows API. _inout means the function reads from and writes to the buffer, and _opt means it is optional (i.e. it can be null).

answered Jan 17 '18 at 13:31

jsheeran

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Meaning of __inout_opt given before function parameter

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