Update.

	* libio/vswprintf.c (_IO_vswprintf): Fix return value handling
	which is different from snprintf.
	* libio/tst_swprintf.c: Add tests for too small output buffer.

2 files changed, 55 insertions, 23 deletions

diff --git a/libio/tst_swprintf.c b/libio/tst_swprintf.c
index 67d10a006d..dc16db0a0c 100644
--- a/libio/tst_swprintf.c
+++ b/libio/tst_swprintf.c
@@ -1,42 +1,76 @@
 #include <stdio.h>
 #include <wchar.h>
+#include <sys/types.h>
+
+
+static wchar_t buf[100];
+#define nbuf (sizeof (buf) / sizeof (buf[0]))
+static const struct
+{
+  size_t n;
+  const char *str;
+  ssize_t exp;
+} tests[] =
+  {
+    { nbuf, "hello world", 11 },
+    { 0, "hello world", -1 },
+    { 0, "", -1 },
+    { nbuf, "", 0 }
+  };
 
 int
 main (int argc, char *argv[])
 {
-  wchar_t buf[100];
   int n;
   int result = 0;
 
   puts ("test 1");
-  n = swprintf (buf, sizeof (buf) / sizeof (buf[0]), L"Hello %s", "world");
+  n = swprintf (buf, nbuf, L"Hello %s", "world");
   if (n != 11)
     {
       printf ("incorrect return value: %d instead of 11\n", n);
       result = 1;
     }
-
-  if (wcscmp (buf, L"Hello world") != 0)
+  else if (wcscmp (buf, L"Hello world") != 0)
     {
       printf ("incorrect string: L\"%ls\" instead of L\"Hello world\"\n", buf);
       result = 1;
     }
 
   puts ("test 2");
-  n = swprintf (buf, sizeof (buf) / sizeof (buf[0]), L"Is this >%g< 3.1?",
-		3.1);
+  n = swprintf (buf, nbuf, L"Is this >%g< 3.1?", 3.1);
   if (n != 18)
-{
+    {
       printf ("incorrect return value: %d instead of 18\n", n);
       result = 1;
     }
-
-  if (wcscmp (buf, L"Is this >3.1< 3.1?") != 0)
+  else if (wcscmp (buf, L"Is this >3.1< 3.1?") != 0)
     {
       printf ("incorrect string: L\"%ls\" instead of L\"Is this >3.1< 3.1?\"\n",
 	      buf);
       result = 1;
     }
 
+  for (n = 0; n < sizeof (tests) / sizeof (tests[0]); ++n)
+    {
+      ssize_t res = swprintf (buf, tests[n].n, L"%s", tests[n].str);
+
+      if (tests[n].exp < 0 && res >= 0)
+	{
+	  printf ("swprintf (buf, %Zu, L\"%%s\", \"%s\") expected to fail\n",
+		  tests[n].n, tests[n].str);
+	  result = 1;
+	}
+      else if (tests[n].exp >= 0 && tests[n].exp != res)
+	{
+	  printf ("swprintf (buf, %Zu, L\"%%s\", \"%s\") expected to return %Zd, but got %Zd\n",
+		  tests[n].n, tests[n].str, tests[n].exp, res);
+	  result = 1;
+	}
+      else
+	printf  ("swprintf (buf, %Zu, L\"%%s\", \"%s\") OK\n",
+		 tests[n].n, tests[n].str);
+    }
+
   return result;
 }
diff --git a/libio/vswprintf.c b/libio/vswprintf.c
index 25274926f6..00dc62c902 100644
--- a/libio/vswprintf.c
+++ b/libio/vswprintf.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1994, 1997, 1999, 2000 Free Software Foundation, Inc.
+/* Copyright (C) 1994, 1997, 1999, 2000, 2001 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
@@ -54,11 +54,6 @@ _IO_wstrn_overflow (fp, c)
 
   if (fp->_wide_data->_IO_buf_base != snf->overflow_buf)
     {
-      /* Terminate the string.  We know that there is room for at
-	 least one more character since we initialized the stream with
-	 a size to make this possible.  */
-      *fp->_wide_data->_IO_write_ptr = '\0';
-
       _IO_wsetb (fp, snf->overflow_buf,
 		 snf->overflow_buf + (sizeof (snf->overflow_buf)
 				      / sizeof (wchar_t)), 0);
@@ -120,13 +115,10 @@ _IO_vswprintf (string, maxlen, format, args)
   sf.f._sbf._f._lock = &lock;
 #endif
 
-  /* We need to handle the special case where MAXLEN is 0.  Use the
-     overflow buffer right from the start.  */
   if (maxlen == 0)
-    {
-      string = sf.overflow_buf;
-      maxlen = sizeof (sf.overflow_buf) / sizeof (wchar_t);
-    }
+    /* Since we have to write at least the terminating L'\0' a buffer
+       length of zero always makes the function fail.  */
+    return -1;
 
   _IO_no_init (&sf.f._sbf._f, 0, 0, &wd, &_IO_wstrn_jumps);
   _IO_fwide (&sf.f._sbf._f, 1);
@@ -134,8 +126,14 @@ _IO_vswprintf (string, maxlen, format, args)
   _IO_wstr_init_static (&sf.f._sbf._f, string, maxlen - 1, string);
   ret = _IO_vfwprintf ((_IO_FILE *) &sf.f._sbf, format, args);
 
-  if (sf.f._sbf._f._wide_data->_IO_buf_base != sf.overflow_buf)
-    *sf.f._sbf._f._wide_data->_IO_write_ptr = '\0';
+  if (sf.f._sbf._f._wide_data->_IO_buf_base == sf.overflow_buf)
+    /* ISO C99 requires swprintf/vswprintf to return an error if the
+       output does not fit int he provided buffer.  */
+    return -1;
+
+  /* Terminate the string.  */
+  *sf.f._sbf._f._wide_data->_IO_write_ptr = '\0';
+
   return ret;
 }