2019-05-15  Andreas Schwab  <schwab@suse.de>

	[BZ #20568]
	* libio/wfileops.c (_IO_wfile_sync): Correct last argument to
	__codecvt_do_length.
	* libio/Makefile (tests): Add tst-wfile-sync.
	($(objpfx)tst-wfile-sync.out): Depend on $(gen-locales).
	* libio/tst-wfile-sync.c: New file.
	* libio/tst-wfile-sync.input: New file.

Index: glibc-2.29/libio/Makefile
===================================================================
--- glibc-2.29.orig/libio/Makefile
+++ glibc-2.29/libio/Makefile
@@ -65,7 +65,7 @@ tests = tst_swprintf tst_wprintf tst_sws
 	tst-setvbuf1 tst-popen1 tst-fgetwc bug-wsetpos tst-fseek \
 	tst-fwrite-error tst-ftell-partial-wide tst-ftell-active-handler \
 	tst-ftell-append tst-fputws tst-bz22415 tst-fgetc-after-eof \
-	tst-sprintf-ub tst-sprintf-chk-ub
+	tst-sprintf-ub tst-sprintf-chk-ub tst-wfile-sync
 
 tests-internal = tst-vtables tst-vtables-interposed tst-readline
 
@@ -212,6 +212,7 @@ $(objpfx)tst-ungetwc1.out: $(gen-locales
 $(objpfx)tst-ungetwc2.out: $(gen-locales)
 $(objpfx)tst-widetext.out: $(gen-locales)
 $(objpfx)tst_wprintf2.out: $(gen-locales)
+$(objpfx)tst-wfile-sync.out: $(gen-locales)
 endif
 
 $(objpfx)test-freopen.out: test-freopen.sh $(objpfx)test-freopen
Index: glibc-2.29/libio/tst-wfile-sync.c
===================================================================
--- /dev/null
+++ glibc-2.29/libio/tst-wfile-sync.c
@@ -0,0 +1,39 @@
+/* Test that _IO_wfile_sync does not crash (bug 20568).
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <locale.h>
+#include <stdio.h>
+#include <wchar.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+
+static int
+do_test (void)
+{
+  TEST_VERIFY_EXIT (setlocale (LC_ALL, "de_DE.UTF-8") != NULL);
+  /* Fill the stdio buffer and advance the read pointer.  */
+  TEST_VERIFY_EXIT (fgetwc (stdin) != WEOF);
+  /* This calls _IO_wfile_sync, it should not crash.  */
+  TEST_VERIFY_EXIT (setvbuf (stdin, NULL, _IONBF, 0) == 0);
+  /* Verify that the external file offset has been synchronized.  */
+  TEST_COMPARE (xlseek (0, 0, SEEK_CUR), 1);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
Index: glibc-2.29/libio/tst-wfile-sync.input
===================================================================
--- /dev/null
+++ glibc-2.29/libio/tst-wfile-sync.input
@@ -0,0 +1 @@
+This is a test of _IO_wfile_sync.
Index: glibc-2.29/libio/wfileops.c
===================================================================
--- glibc-2.29.orig/libio/wfileops.c
+++ glibc-2.29/libio/wfileops.c
@@ -508,11 +508,12 @@ _IO_wfile_sync (FILE *fp)
 	     generate the wide characters up to the current reading
 	     position.  */
 	  int nread;
-
+	  size_t wnread = (fp->_wide_data->_IO_read_ptr
+			   - fp->_wide_data->_IO_read_base);
 	  fp->_wide_data->_IO_state = fp->_wide_data->_IO_last_state;
 	  nread = (*cv->__codecvt_do_length) (cv, &fp->_wide_data->_IO_state,
 					      fp->_IO_read_base,
-					      fp->_IO_read_end, delta);
+					      fp->_IO_read_end, wnread);
 	  fp->_IO_read_ptr = fp->_IO_read_base + nread;
 	  delta = -(fp->_IO_read_end - fp->_IO_read_base - nread);
 	}