Re: Sometimes the output to the stdout in Windows disappears - Mailing list pgsql-hackers

I wrote:
> Alexander Lakhin <exclusion@gmail.com> writes:
>> What bothers me is:
>>     There must be a call to *WSACleanup* for each successful call to
>>     WSAStartup
>>     <https://docs.microsoft.com/en-us/windows/desktop/api/winsock/nf-winsock-wsastartup>.

> Yeah, that is a very odd statement.  Surely, the Windows kernel manages
> to cope if a program crashes without having done that.  So what exactly
> is the downside of intentionally not doing it?

A bit of grepping showed me that the backend, initdb, and pg_regress
all call WSAStartup without ever doing WSACleanup, and we've seen no
ill effects from that.  So it seems clear that this documentation can
safely be ignored.

I propose the attached patch.  If this doesn't cause buildfarm problems,
perhaps we should back-patch it.

BTW, I notice that libpq is asking WSAStartup for Winsock version 1.1,
which is remarkably ancient.  Almost everyplace else is asking for
version 2.2, which has been current for a decade or two.  Shouldn't
we update that?  (It occurs to me to wonder if this in itself is
some kind of problem; I wonder how well Winsock works when there are
requests for different API versions in the same program.)

            regards, tom lane

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3315f1dd05..de60281fcb 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -91,21 +91,6 @@
     </para>
    </warning>

-   <note>
-    <para>
-     On Windows, there is a way to improve performance if a single
-     database connection is repeatedly started and shutdown.  Internally,
-     libpq calls <function>WSAStartup()</function> and <function>WSACleanup()</function> for connection startup
-     and shutdown, respectively.  <function>WSAStartup()</function> increments an internal
-     Windows library reference count which is decremented by <function>WSACleanup()</function>.
-     When the reference count is just one, calling <function>WSACleanup()</function> frees
-     all resources and all DLLs are unloaded.  This is an expensive
-     operation.  To avoid this, an application can manually call
-     <function>WSAStartup()</function> so resources will not be freed when the last database
-     connection is closed.
-    </para>
-   </note>
-
    <variablelist>
     <varlistentry id="libpq-PQconnectdbParams">
      <term><function>PQconnectdbParams</function><indexterm><primary>PQconnectdbParams</primary></indexterm></term>
diff --git a/src/bin/pg_dump/parallel.c b/src/bin/pg_dump/parallel.c
index a967e11378..b51cc76c7d 100644
--- a/src/bin/pg_dump/parallel.c
+++ b/src/bin/pg_dump/parallel.c
@@ -229,19 +229,6 @@ static char *readMessageFromPipe(int fd);
     (strncmp(msg, prefix, strlen(prefix)) == 0)


-/*
- * Shutdown callback to clean up socket access
- */
-#ifdef WIN32
-static void
-shutdown_parallel_dump_utils(int code, void *unused)
-{
-    /* Call the cleanup function only from the main thread */
-    if (mainThreadId == GetCurrentThreadId())
-        WSACleanup();
-}
-#endif
-
 /*
  * Initialize parallel dump support --- should be called early in process
  * startup.  (Currently, this is called whether or not we intend parallel
@@ -267,8 +254,7 @@ init_parallel_dump_utils(void)
             pg_log_error("WSAStartup failed: %d", err);
             exit_nicely(1);
         }
-        /* ... and arrange to shut it down at exit */
-        on_exit_nicely(shutdown_parallel_dump_utils, NULL);
+
         parallel_init_done = true;
     }
 #endif
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index af27fee6b5..704c9e2f79 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -3871,23 +3871,30 @@ makeEmptyPGconn(void)
 #ifdef WIN32

     /*
-     * Make sure socket support is up and running.
+     * Make sure socket support is up and running in this process.
+     *
+     * Note: the Windows documentation says that we should eventually do a
+     * matching WSACleanup() call, but experience suggests that that is at
+     * least as likely to cause problems as fix them.  So we don't.
      */
-    WSADATA        wsaData;
+    static bool wsastartup_done = false;

-    if (WSAStartup(MAKEWORD(1, 1), &wsaData))
-        return NULL;
+    if (!wsastartup_done)
+    {
+        WSADATA        wsaData;
+
+        if (WSAStartup(MAKEWORD(1, 1), &wsaData) != 0)
+            return NULL;
+        wsastartup_done = true;
+    }
+
+    /* Forget any earlier error */
     WSASetLastError(0);
-#endif
+#endif                            /* WIN32 */

     conn = (PGconn *) malloc(sizeof(PGconn));
     if (conn == NULL)
-    {
-#ifdef WIN32
-        WSACleanup();
-#endif
         return conn;
-    }

     /* Zero all pointers and booleans */
     MemSet(conn, 0, sizeof(PGconn));
@@ -4080,10 +4087,6 @@ freePGconn(PGconn *conn)
     termPQExpBuffer(&conn->workBuffer);

     free(conn);
-
-#ifdef WIN32
-    WSACleanup();
-#endif
 }

 /*