From 43a7cdd03dafc0fb5a28027c15a9fe20354beadc Mon Sep 17 00:00:00 2001
From: Kristoffer Gryte <krisgry@git>
Date: Sat, 9 May 2026 22:39:51 +0200
Subject: [PATCH] DUNE/Utils/String: fix rightTrimInPlace underflow on
 empty/all-ws input

Empty strings made `r = str - 1` and the loop then read one byte before
the buffer; all-whitespace strings walked off the front the same way.
Caught by ASan via Parsers/Config::parseFile when getOptionAndValue
returned rv==2 (key with no value) and arg was the empty string.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 src/DUNE/Utils/String.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/DUNE/Utils/String.cpp b/src/DUNE/Utils/String.cpp
index 9851f484ff..5045f137df 100644
--- a/src/DUNE/Utils/String.cpp
+++ b/src/DUNE/Utils/String.cpp
@@ -82,9 +82,12 @@ namespace DUNE
     void
     String::rightTrimInPlace(char* str)
     {
-      char* r = str + std::strlen(str) - 1; // Rightmost character
+      size_t len = std::strlen(str);
+      if (len == 0)
+        return;
 
-      for (; isspace(*r); --r)
+      char* r = str + len - 1; // Rightmost character
+      for (; r >= str && isspace(static_cast<unsigned char>(*r)); --r)
         *r = 0;
     }