bpo-30237: Output error when ReadConsole is canceled by CancelSynchronousIo. (GH-7911)

Misc/NEWS.d/next/Windows/2018-06-25-09-33-48.bpo-30237.EybiZA.rst

+Output error when ReadConsole is canceled by CancelSynchronousIo instead of
+crashing.

Modules/_io/winconsoleio.c

@@ -556,7 +556,8 @@ read_console_w(HANDLE handle, DWORD maxlen, DWORD *readlen) {
     Py_BEGIN_ALLOW_THREADS
     DWORD off = 0;
     while (off < maxlen) {
-        DWORD n, len = min(maxlen - off, BUFSIZ);
+        DWORD n = (DWORD)-1; 
+        DWORD len = min(maxlen - off, BUFSIZ);
         SetLastError(0);
         BOOL res = ReadConsoleW(handle, &buf[off], len, &n, NULL);
 
@@ -564,6 +565,9 @@ read_console_w(HANDLE handle, DWORD maxlen, DWORD *readlen) {
             err = GetLastError();
             break;
         }
+        if (n == (DWORD)-1 && (err = GetLastError()) == ERROR_OPERATION_ABORTED) {
+            break;
+        }
         if (n == 0) {
             err = GetLastError();
             if (err != ERROR_OPERATION_ABORTED)

Parser/myreadline.c

@@ -109,7 +109,7 @@ _PyOS_WindowsConsoleReadline(HANDLE hStdIn)
     char *buf = NULL;
     int err = 0;
 
-    n_read = 0;
+    n_read = (DWORD)-1;
     total_read = 0;
     wbuf = wbuf_local;
     wbuflen = sizeof(wbuf_local) / sizeof(wbuf_local[0]) - 1;
@@ -121,6 +121,9 @@ _PyOS_WindowsConsoleReadline(HANDLE hStdIn)
             err = GetLastError();
             goto exit;
         }
+        if (n_read == (DWORD)-1 && (err = GetLastError()) == ERROR_OPERATION_ABORTED) {
+            break;
+        }
         if (n_read == 0) {
             int s;
             err = GetLastError();