From b0a74f162e1cb7db9dd6a8fbaed9bfbf8ae17a10 Mon Sep 17 00:00:00 2001
From: Patrick Pelissier <patrick.pelissier@gmail.com>
Date: Thu, 5 Nov 2020 22:51:28 +0100
Subject: [PATCH] Fix string_printf in case of error in formating.

---
 m-string.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/m-string.h b/m-string.h
index d76a08b8..b36677cb 100644
--- a/m-string.h
+++ b/m-string.h
@@ -792,8 +792,12 @@ string_printf (string_t v, const char format[], ...)
     size = vsnprintf (ptr, alloc, format, args);
     M_ASSERT (size > 0 && (size_t)size < alloc);
   }
-  if (size >= 0) {
+  if (M_LIKELY (size >= 0)) {
     stringi_set_size(v, (size_t) size);
+  } else {
+    // An error occured during the conversion: Assign an empty string.
+    stringi_set_size(v, 0);
+    ptr[0] = 0;
   }
   va_end (args);
   STRINGI_CONTRACT (v);
@@ -1411,7 +1415,7 @@ string_it(string_it_t it, const string_t str)
 }
 
 /* Set the iterator to the end of string 
-   The iterator references therefore nothong.
+   The iterator references therefore nothing.
 */
 static inline void
 string_it_end(string_it_t it, const string_t str)