From 0cef325b07b18fff9da30f9a4b838ae2f617e2f6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Antonio=20S=C3=A1nchez?= <cantonios@google.com>
Date: Mon, 31 Jul 2023 19:18:45 +0000
Subject: [PATCH] Fix another UB access.

---
 Eigen/src/Core/SolveTriangular.h                 | 5 +++++
 Eigen/src/Core/products/TriangularMatrixMatrix.h | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Core/SolveTriangular.h b/Eigen/src/Core/SolveTriangular.h
index 71d6f8539..23df5082a 100644
--- a/Eigen/src/Core/SolveTriangular.h
+++ b/Eigen/src/Core/SolveTriangular.h
@@ -97,6 +97,11 @@ struct triangular_solver_selector<Lhs,Rhs,Side,Mode,NoUnrolling,Dynamic>
     typedef internal::gemm_blocking_space<(Rhs::Flags&RowMajorBit) ? RowMajor : ColMajor,Scalar,Scalar,
               Rhs::MaxRowsAtCompileTime, Rhs::MaxColsAtCompileTime, Lhs::MaxRowsAtCompileTime,4> BlockingType;
 
+    // Nothing to solve.
+    if (actualLhs.size() == 0 || rhs.size() == 0) {
+      return;
+    }
+
     BlockingType blocking(rhs.rows(), rhs.cols(), size, 1, false);
 
     triangular_solve_matrix<Scalar,Index,Side,Mode,LhsProductTraits::NeedToConjugate,(int(Lhs::Flags) & RowMajorBit) ? RowMajor : ColMajor,
diff --git a/Eigen/src/Core/products/TriangularMatrixMatrix.h b/Eigen/src/Core/products/TriangularMatrixMatrix.h
index 94eabdc2f..80c98dd0d 100644
--- a/Eigen/src/Core/products/TriangularMatrixMatrix.h
+++ b/Eigen/src/Core/products/TriangularMatrixMatrix.h
@@ -424,7 +424,7 @@ struct triangular_product_impl<Mode,LhsIsTriangular,Lhs,false,Rhs,false>
 
     // Empty product, return early.  Otherwise, we get `nullptr` use errors below when we try to access
     // coeffRef(0,0).
-    if (a_lhs.size() == 0 || a_rhs.size() == 0) {
+    if (lhs.size() == 0 || rhs.size() == 0) {
       return;
     }