fwrite ERRNO 22 with big (?) size

[VladimirF]

Ok, now i've added the checks.
I've omitted them since they did not seem relevant to me.

So where exactly in your code do you see that errno is 22?
Did you step through your code under debugger?
What is the value of written_bytes? content_length? And what is its type?
Please note that errno is a global variable, it could be set in some other place in your code.
For example, if your parsed_request->body is 0, you bypass the line

errno=0;