From 1d21d62fbc1431c00c6dd7e65f1b35cea30bd872 Mon Sep 17 00:00:00 2001
From: Pavel Guzenfeld <pavelguzenfeld@gmail.com>
Date: Sat, 21 Mar 2026 15:38:27 +0000
Subject: [PATCH] Fix computeInverseAndDetWithCheck for dynamic result matrices

libeigen/eigen!2312

Closes #2917
---
 Eigen/src/LU/InverseImpl.h |  5 ++---
 test/inverse.cpp           | 26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/Eigen/src/LU/InverseImpl.h b/Eigen/src/LU/InverseImpl.h
index 5c24dfec1..58ac305bc 100644
--- a/Eigen/src/LU/InverseImpl.h
+++ b/Eigen/src/LU/InverseImpl.h
@@ -308,8 +308,9 @@ inline void MatrixBase<Derived>::computeInverseAndDetWithCheck(ResultType& inver
                                                                typename ResultType::Scalar& determinant,
                                                                bool& invertible,
                                                                const RealScalar& absDeterminantThreshold) const {
-  // i'd love to put some static assertions there, but SFINAE means that they have no effect...
+  EIGEN_STATIC_ASSERT_SAME_MATRIX_SIZE(Derived, ResultType)
   eigen_assert(rows() == cols());
+  inverse.resize(rows(), cols());
   // for 2x2, it's worth giving a chance to avoid evaluating.
   // for larger sizes, evaluating has negligible cost and limits code size.
   typedef std::conditional_t<RowsAtCompileTime == 2,
@@ -343,8 +344,6 @@ template <typename ResultType>
 inline void MatrixBase<Derived>::computeInverseWithCheck(ResultType& inverse, bool& invertible,
                                                          const RealScalar& absDeterminantThreshold) const {
   Scalar determinant;
-  // i'd love to put some static assertions there, but SFINAE means that they have no effect...
-  eigen_assert(rows() == cols());
   computeInverseAndDetWithCheck(inverse, determinant, invertible, absDeterminantThreshold);
 }
 
diff --git a/test/inverse.cpp b/test/inverse.cpp
index d564db404..367bf24ed 100644
--- a/test/inverse.cpp
+++ b/test/inverse.cpp
@@ -58,6 +58,32 @@ void inverse_for_fixed_size(const MatrixType& m1, std::enable_if_t<MatrixType::S
     VERIFY_IS_APPROX((m5.template topLeftCorner<MatrixType::RowsAtCompileTime, MatrixType::ColsAtCompileTime>()),
                      m2.inverse());
   }
+
+  // check that computeInverseAndDetWithCheck resizes dynamic result matrix (issue #2917)
+  {
+    typedef Matrix<Scalar, Dynamic, Dynamic> DynamicMatrix;
+    DynamicMatrix m_dyn_inv;
+    Scalar det_dyn;
+    bool inv_dyn;
+    m1.computeInverseAndDetWithCheck(m_dyn_inv, det_dyn, inv_dyn);
+    VERIFY(inv_dyn);
+    VERIFY_IS_EQUAL(m_dyn_inv.rows(), m1.rows());
+    VERIFY_IS_EQUAL(m_dyn_inv.cols(), m1.cols());
+    VERIFY_IS_APPROX(identity, m1 * m_dyn_inv);
+    VERIFY_IS_APPROX(det_dyn, m1.determinant());
+  }
+
+  // check that computeInverseWithCheck resizes dynamic result matrix
+  {
+    typedef Matrix<Scalar, Dynamic, Dynamic> DynamicMatrix;
+    DynamicMatrix m_dyn_inv;
+    bool inv_dyn;
+    m1.computeInverseWithCheck(m_dyn_inv, inv_dyn);
+    VERIFY(inv_dyn);
+    VERIFY_IS_EQUAL(m_dyn_inv.rows(), m1.rows());
+    VERIFY_IS_EQUAL(m_dyn_inv.cols(), m1.cols());
+    VERIFY_IS_APPROX(identity, m1 * m_dyn_inv);
+  }
 }
 
 template <typename MatrixType>