Expect EWOULDBLOCK from a non-blocking connect() call only on Windows.

tglsfdc · tglsfdc · commit a099482c86d8 · 2013-06-27T12:36:44.000-04:00
On Unix-ish platforms, EWOULDBLOCK may be the same as EAGAIN, which is *not* a success return, at least not on Linux. We need to treat it as a failure to avoid giving a misleading error message. Per the Single Unix Spec, only EINPROGRESS and EINTR returns indicate that the connection attempt is in progress. On Windows, on the other hand, EWOULDBLOCK (WSAEWOULDBLOCK) is the expected case. We must accept EINPROGRESS as well because Cygwin will return that, and it doesn't seem worth distinguishing Cygwin from native Windows here. It's not very clear whether EINTR can occur on Windows, but let's leave that part of the logic alone in the absence of concrete trouble reports. Also, remove the test for errno == 0, effectively reverting commit da9501b, which AFAICS was just a thinko; or at best it might have been a workaround for a platform-specific bug, which we can hope is gone now thirteen years later. In any case, since libpq makes no effort to reset errno to zero before calling connect(), it seems unlikely that that test has ever reliably done anything useful. Andres Freund and Tom Lane
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
@@ -1780,9 +1780,10 @@ PQconnectPoll(PGconn *conn)
 								addr_cur->ai_addrlen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
+#ifdef WIN32
 							SOCK_ERRNO == EWOULDBLOCK ||
-							SOCK_ERRNO == EINTR ||
-							SOCK_ERRNO == 0)
+#endif
+							SOCK_ERRNO == EINTR)
 						{
 							/*
 							 * This is fine - we're in non-blocking mode, and

Original file line number	Diff line number	Diff line change
`@@ -1780,9 +1780,10 @@ PQconnectPoll(PGconn *conn)`
`1780`	`1780`	`addr_cur->ai_addrlen) < 0)`
`1781`	`1781`	`{`
`1782`	`1782`	`if (SOCK_ERRNO == EINPROGRESS \|\|`
	`1783`	`+#ifdef WIN32`
`1783`	`1784`	`SOCK_ERRNO == EWOULDBLOCK \|\|`
`1784`		`- SOCK_ERRNO == EINTR \|\|`
`1785`		`- SOCK_ERRNO == 0)`
	`1785`	`+#endif`
	`1786`	`+ SOCK_ERRNO == EINTR)`
`1786`	`1787`	`{`
`1787`	`1788`	`/*`
`1788`	`1789`	`* This is fine - we're in non-blocking mode, and`