Fix duplicate output on console resize event (#806)

* Fix the SIGWINCH interrupt makes the write operation think its failed, and causes it to try again.

xlink directvt/vtm#819 (comment)

> When a window resize event is received (terminal generates WINDOW_BUFFER_SIZE_EVENT event when switching between alternate/normal buffer mode), the errno becomes EINTR which causes the write operation think its failed.

potentially fixes PowerShell/Win32-OpenSSH#2275

* #2275: Add comments to the fix the SIGWINCH interrupt makes the write operation think its failed

Author: o-sdn-o

contrib/win32/win32compat/console.c

@@ -225,17 +225,6 @@ ConEnterRawMode()
 	ScrollBottom = ConVisibleWindowHeight();
 
 	in_raw_mode = 1;
-
-	/*
-	Consume and ignore the first WINDOW_BUFFER_SIZE_EVENT, as we've triggered it ourselves by updating the console settings above.
-	Not consuming this event can cause a race condition: the event can cause a write to the console to be printed twice as the
-	SIGWINCH interrupt makes the write operation think its failed, and causes it to try again.
-	*/
-	INPUT_RECORD peek_input;
-	int out_count = 0;
-	if (PeekConsoleInputW(GetConsoleInputHandle(), &peek_input, 1, &out_count) && peek_input.EventType == WINDOW_BUFFER_SIZE_EVENT) {
-		ReadConsoleInputW(GetConsoleInputHandle(), &peek_input, 1, &out_count);
-	}
 }
 
 /* Used to Uninitialize the Console */

contrib/win32/win32compat/signal.c

@@ -228,9 +228,9 @@ sw_process_pending_signals()
 		if (sigismember(&pending_tmp, exp[i])) {
 			if (sig_handlers[exp[i]] != W32_SIG_IGN) {
 				w32_raise(exp[i]);
-				/* dont error EINTR for SIG_ALRM, */
-				/* sftp client is not expecting it */
-				if (exp[i] != W32_SIGALRM)
+				/* don't set errno=EINTR on SIGALRM, sftp client is not expecting it */
+				/* don't set errno=EINTR on SIGWINCH in order to avoid breaking the sequence of waiting for completion of IO operations. */
+				if (exp[i] != W32_SIGALRM && exp[i] != W32_SIGWINCH)
 					sig_int = TRUE;
 			} else if (exp[i] == W32_SIGCHLD) /*if SIGCHLD is SIG_IGN, reap zombies*/
 				sw_cleanup_child_zombies();