From 115b8e214a0d7b22e63dfce130268ce2c96c7d03 Mon Sep 17 00:00:00 2001
From: Kawe Mazidjatari <48657826+Mauler125@users.noreply.github.com>
Date: Tue, 6 Feb 2024 14:36:01 +0100
Subject: [PATCH] utility: fix STL string formatter bug

Must reserve a buf size of len+1 before resizing it, else we are 1 byte too short when copying the entire string. Also just clear when 0.
---
 r5dev/tier0/utility.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/r5dev/tier0/utility.cpp b/r5dev/tier0/utility.cpp
index dab4e454..f3105773 100644
--- a/r5dev/tier0/utility.cpp
+++ b/r5dev/tier0/utility.cpp
@@ -1086,14 +1086,20 @@ string FormatV(const char* szFormat, va_list args)
     assert(iLen >= 0);
     string result;
 
-    if (iLen < 0)
+    if (iLen <= 0)
     {
         result.clear();
     }
     else
     {
+        // NOTE: reserve enough buffer size for the string + the terminating
+        // NULL character, then resize it to just the string len so we don't
+        // count the NULL character in the string's size (i.e. when calling
+        // string::size()).
+        result.reserve(iLen+1);
         result.resize(iLen);
-        std::vsnprintf(&result[0], iLen+sizeof(char), szFormat, args);
+
+        std::vsnprintf(&result[0], iLen+1, szFormat, args);
     }
 
     return result;