Re: BUG #14999: pg_rewind corrupts control file global/pg_control

> On 27 February 2018 at 02:24, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> Note that I am still not completely happy with the
> handling in errno in some newly-added code paths..

It maybe a stupid question, but why do you need to reset errno here? Is it to
avoid its value being carried from previous calls of `open_target_file`? In
this case if you put the code with `errno == EACCESS` under the if condition
`if (dstfd < 0)`, then as far as I remember you should always get relevant
errno. At the same time maybe it's valid to reset `errno` before `open`, like
with `getpriority`:

For some system calls and library functions (e.g., getpriority(2)), -1 is
a valid return on success. In such cases, a successful return can be
distinguished from an error return by setting errno to zero before the
call, and then, if the call returns a status that indicates that an error
may have occurred, checking to see if errno has a nonzero value.