A method with return type size_t returns negative value

[Jing LV]

Hello,

I found a problem in windows/native/java/io/io_util_md.c, method
handleRead(). The return type of the method is size_t, which is defined
as unsigned int. However we see the method would return negative values
while it meets some error. This may be a problem as the API comsumer and
later developer may have misunderstand it. I suggest modify it to
ssize_t (or SSIZE_T as it is on windows).
Any comments?

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Best Regards,
Jimmy, Jing LV