From 02d972412855251acc3a7a60a7ed96078ff3401b Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Fri, 3 Jan 2025 19:10:25 -0800
Subject: [PATCH] SmallMatrix: Assert Lower Bound Index

With 1-based indices, it is easy to access `0` and be
out-of-bounds. Add an assert for the lower bound of the index
range as well.
---
 Src/Base/AMReX_SmallMatrix.H | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Src/Base/AMReX_SmallMatrix.H b/Src/Base/AMReX_SmallMatrix.H
index 05305d1839..b1b6ee3040 100644
--- a/Src/Base/AMReX_SmallMatrix.H
+++ b/Src/Base/AMReX_SmallMatrix.H
@@ -100,6 +100,7 @@ namespace amrex {
                 --i;
                 --j;
             }
+            AMREX_ASSERT(i >= 0 && j >= 0);
             AMREX_ASSERT(i < NRows && j < NCols);
             if constexpr (ORDER == Order::F) {
                 return m_mat[i+j*NRows];
@@ -116,6 +117,7 @@ namespace amrex {
                 --i;
                 --j;
             }
+            AMREX_ASSERT(i >= 0 && j >= 0);
             AMREX_ASSERT(i < NRows && j < NCols);
             if constexpr (ORDER == Order::F) {
                 return m_mat[i+j*NRows];
@@ -132,6 +134,7 @@ namespace amrex {
             if constexpr (StartIndex == 1) {
                 --i;
             }
+            AMREX_ASSERT(i >= 0);
             AMREX_ASSERT(i < NRows*NCols);
             return m_mat[i];
         }
@@ -144,6 +147,7 @@ namespace amrex {
             if constexpr (StartIndex == 1) {
                 --i;
             }
+            AMREX_ASSERT(i >= 0);
             AMREX_ASSERT(i < NRows*NCols);
             return m_mat[i];
         }
@@ -156,6 +160,7 @@ namespace amrex {
             if constexpr (StartIndex == 1) {
                 --i;
             }
+            AMREX_ASSERT(i >= 0);
             AMREX_ASSERT(i < NRows*NCols);
             return m_mat[i];
         }
@@ -168,6 +173,7 @@ namespace amrex {
             if constexpr (StartIndex == 1) {
                 --i;
             }
+            AMREX_ASSERT(i >= 0);
             AMREX_ASSERT(i < NRows*NCols);
             return m_mat[i];
         }