From ac0d957f26a8214835df6cfcd0bfcd89d6ce863e Mon Sep 17 00:00:00 2001
From: Jussi Kivilinna <jussi.kivilinna@haltian.com>
Date: Fri, 17 Mar 2017 17:32:44 -0600
Subject: [PATCH] libc: printf: fix precision for string formatting. Fixes use
 of format precision to truncate input string.

---
 libc/stdio/lib_libvsprintf.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/libc/stdio/lib_libvsprintf.c b/libc/stdio/lib_libvsprintf.c
index 894f040453..1a3501c704 100644
--- a/libc/stdio/lib_libvsprintf.c
+++ b/libc/stdio/lib_libvsprintf.c
@@ -1171,9 +1171,7 @@ int lib_vsprintf(FAR struct lib_outstream_s *obj, FAR const IPTR char *src,
   FAR char        *ptmp;
 #ifndef CONFIG_NOPRINTF_FIELDWIDTH
   int             width;
-#ifdef CONFIG_LIBC_FLOATINGPOINT
   int             trunc;
-#endif
   uint8_t         fmt;
 #endif
   uint8_t         flags;
@@ -1215,9 +1213,7 @@ int lib_vsprintf(FAR struct lib_outstream_s *obj, FAR const IPTR char *src,
 #ifndef CONFIG_NOPRINTF_FIELDWIDTH
       fmt   = FMT_RJUST;
       width = 0;
-#ifdef CONFIG_LIBC_FLOATINGPOINT
       trunc = 0;
-#endif
 #endif
 
       /* Process each format qualifier. */
@@ -1265,10 +1261,8 @@ int lib_vsprintf(FAR struct lib_outstream_s *obj, FAR const IPTR char *src,
               int value = va_arg(ap, int);
               if (IS_HASDOT(flags))
                 {
-#ifdef CONFIG_LIBC_FLOATINGPOINT
                   trunc = value;
                   SET_HASASTERISKTRUNC(flags);
-#endif
                 }
               else
                 {
@@ -1307,9 +1301,7 @@ int lib_vsprintf(FAR struct lib_outstream_s *obj, FAR const IPTR char *src,
 
               if (IS_HASDOT(flags))
                 {
-#ifdef CONFIG_LIBC_FLOATINGPOINT
                   trunc = n;
-#endif
                 }
               else
                 {
@@ -1361,6 +1353,7 @@ int lib_vsprintf(FAR struct lib_outstream_s *obj, FAR const IPTR char *src,
         {
 #ifndef CONFIG_NOPRINTF_FIELDWIDTH
           int swidth;
+          int left;
 #endif
           /* Get the string to output */
 
@@ -1375,13 +1368,21 @@ int lib_vsprintf(FAR struct lib_outstream_s *obj, FAR const IPTR char *src,
            */
 
 #ifndef CONFIG_NOPRINTF_FIELDWIDTH
-          swidth = strlen(ptmp);
+          swidth = (IS_HASDOT(flags) && trunc >= 0)
+                      ? strnlen(ptmp, trunc) : strlen(ptmp);
           prejustify(obj, fmt, 0, width, swidth);
+          left = swidth;
 #endif
           /* Concatenate the string into the output */
 
           while (*ptmp)
             {
+#ifndef CONFIG_NOPRINTF_FIELDWIDTH
+              if (left-- <= 0)
+                {
+                  break;
+                }
+#endif
               obj->put(obj, *ptmp);
               ptmp++;
             }