Fix incorrect BLI_snprintf usage

Event though in practice this wasn't causing problems as the fixed size
buffers are generally large enough not to truncate text.

Using the result from `snprint` or `BLI_snprintf` to step over a fixed
size buffer allows for buffer overruns as the returned value is the size
needed to copy the entire string, not the number of bytes copied.

Building strings using this convention with multiple calls:

    ofs += BLI_snprintf(str + ofs, str_len_max - ofs);

.. caused the size argument to become negative,
wrapping it to a large value when cast to the unsigned argument.

1 files changed, 3 insertions, 2 deletions

diff --git a/source/blender/blenkernel/intern/unit.c b/source/blender/blenkernel/intern/unit.c
index 9ae1c754846..3612a26315c 100644
--- a/source/blender/blenkernel/intern/unit.c
+++ b/source/blender/blenkernel/intern/unit.c
@@ -943,7 +943,7 @@ static int unit_scale_str(char *str,
 
     /* Add the addition sign, the bias, and the close parenthesis after the value. */
     int value_end_ofs = find_end_of_value_chars(str, len_max, prev_op_ofs + 2);
-    int len_bias_num = BLI_snprintf(str_tmp, TEMP_STR_SIZE, "+%.9g)", unit->bias);
+    int len_bias_num = BLI_snprintf_rlen(str_tmp, TEMP_STR_SIZE, "+%.9g)", unit->bias);
     if (value_end_ofs + len_bias_num < len_max) {
       memmove(str + value_end_ofs + len_bias_num, str + value_end_ofs, len - value_end_ofs + 1);
       memcpy(str + value_end_ofs, str_tmp, len_bias_num);
@@ -957,7 +957,8 @@ static int unit_scale_str(char *str,
   int len_move = (len - (found_ofs + len_name)) + 1; /* 1+ to copy the string terminator. */
 
   /* "#" Removed later */
-  int len_num = BLI_snprintf(str_tmp, TEMP_STR_SIZE, "*%.9g" SEP_STR, unit->scalar / scale_pref);
+  int len_num = BLI_snprintf_rlen(
+      str_tmp, TEMP_STR_SIZE, "*%.9g" SEP_STR, unit->scalar / scale_pref);
 
   if (len_num > len_max) {
     len_num = len_max;