From a8b75d0a1c1c5254aba566f476b6e512fee92880 Mon Sep 17 00:00:00 2001
From: Dan Baston <dbaston@gmail.com>
Date: Tue, 4 Feb 2025 13:29:50 -0500
Subject: [PATCH] muparser: avoid uncaught exception on invalid variable name

---
 autotest/gdrivers/vrtderived.py      |  7 +++++++
 frmts/vrt/vrtexpression_muparser.cpp | 19 +++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/autotest/gdrivers/vrtderived.py b/autotest/gdrivers/vrtderived.py
index 48cb238dbfdb..90e955a8f806 100755
--- a/autotest/gdrivers/vrtderived.py
+++ b/autotest/gdrivers/vrtderived.py
@@ -1273,6 +1273,13 @@ def test_vrt_pixelfn_expression(
             "exceeds maximum of 100000 set by GDAL_EXPRTK_MAX_EXPRESSION_LENGTH",
             id="expression is too long",
         ),
+        pytest.param(
+            "B[1]",
+            [("B[1]", 3)],
+            "muparser",
+            "Invalid variable name",
+            id="invalid variable name",
+        ),
     ],
 )
 def test_vrt_pixelfn_expression_invalid(
diff --git a/frmts/vrt/vrtexpression_muparser.cpp b/frmts/vrt/vrtexpression_muparser.cpp
index 6245f7115aea..d9e747302c21 100644
--- a/frmts/vrt/vrtexpression_muparser.cpp
+++ b/frmts/vrt/vrtexpression_muparser.cpp
@@ -25,17 +25,31 @@ class MuParserExpression::Impl
   public:
     explicit Impl(std::string_view osExpression)
         : m_osExpression(std::string(osExpression)), m_oVectors{}, m_oParser{},
-          m_adfResults{1}, m_bIsCompiled{false}
+          m_adfResults{1}, m_bIsCompiled{false}, m_bCompileFailed{false}
     {
     }
 
     void Register(std::string_view osVariable, double *pdfValue)
     {
-        m_oParser.DefineVar(std::string(osVariable), pdfValue);
+        try
+        {
+            m_oParser.DefineVar(std::string(osVariable), pdfValue);
+        }
+        catch (const mu::Parser::exception_type &)
+        {
+            CPLError(CE_Failure, CPLE_AppDefined, "Invalid variable name: %s",
+                     std::string(osVariable).c_str());
+            m_bCompileFailed = true;
+        }
     }
 
     CPLErr Compile()
     {
+        if (m_bCompileFailed)
+        {
+            return CE_Failure;
+        }
+
         try
         {
             CPLString tmpExpression(m_osExpression);
@@ -99,6 +113,7 @@ class MuParserExpression::Impl
     mu::Parser m_oParser;
     std::vector<double> m_adfResults;
     bool m_bIsCompiled;
+    bool m_bCompileFailed;
 };
 
 MuParserExpression::MuParserExpression(std::string_view osExpression)