On 25/05/2018 4:14 PM, Ivan Gerasimov wrote:
Hi David!
If gcc, then we already have the same test for both constants in code
with no issues.
For example, java.base/unix/native/libnet/SocketInputStream.c, in
NET_ReadWithTimeout():
result = NET_NonBlockingRead(fd, bufP, len);
if (result == -1 && ((errno == EAGAIN) || (errno ==
EWOULDBLOCK))) {
If javac, then, I was thinking about it too, but I don't have a good
a universal solution to propose right now.
javac should treat these symbolically rather than based on actual
value, so I don't see any issue there. It's the C compiler that sees
the raw value after preprocessing and so sees "duplicate" clauses.
If fact, as UnixContant.java is built from the template file
UnixConstants.java.template, which is processed with cpp preprocessor,
javac also sees the raw values.
So if someone decides to write something like
switch (exc.errno()) {
case UnixConstants.EAGAIN:
case UnixConstants.EWOULDBLOCK:
}
then there will be compile time trouble on some platforms and no issues
on the others.
I was thinking javac wouldn't examine the actual value of the fields,
but it does for switch :(
Oh well.
David
-----
Fortunately, UnixContant class is package private, so it is quite
unlikely to happen.
I was even thinking about proposing a language-level enhancement: If a
switch statement contains duplicate cases *and* these are combined, then
treat them as just one case.
Though the use case it too limited to justify the need :)
With kind regards,
Ivan
