From fd4db67b43bfffded2b20ec5665924f3b663c3e7 Mon Sep 17 00:00:00 2001
From: Jussi Kivilinna <jussi.kivilinna@haltian.com>
Date: Thu, 4 Apr 2019 06:31:25 -0600
Subject: [PATCH] libs/libc/stdio/lib_libvsprintf.c:  Restore support for
 printing NULL string as "(null)".  Legacy printf supported printing "(null)"
 in place for NULL string:

  printf("null: %s\n", NULL); => null: (null).

This commit restores this functionality for new printf library.
---
 libs/libc/stdio/lib_libvsprintf.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/libs/libc/stdio/lib_libvsprintf.c b/libs/libc/stdio/lib_libvsprintf.c
index a5e0ae3ec8..5076697adf 100644
--- a/libs/libc/stdio/lib_libvsprintf.c
+++ b/libs/libc/stdio/lib_libvsprintf.c
@@ -136,6 +136,12 @@ struct arg
   } value;
 };
 
+ /****************************************************************************
+  * Private Constant Data
+  ****************************************************************************/
+
+ static const char g_nullstring[] = "(null)";
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -847,6 +853,11 @@ static int vsprintf_internal(FAR struct lib_outstream_s *stream,
 #else
           pnt = va_arg(ap, FAR char *);
 #endif
+          if (pnt == NULL)
+            {
+              pnt = g_nullstring;
+            }
+
           size = strnlen(pnt, (flags & FL_PREC) ? prec : ~0);
 
         str_lpad: