Fix infinite recursion in ProductBase::coeff() (bug #447)

Triggered by product of dynamic-size 1 x n and n x 1 matrices.
Also, add regression test.

2 files changed, 24 insertions, 2 deletions

diff --git a/Eigen/src/Core/ProductBase.h b/Eigen/src/Core/ProductBase.h
index 8dccf6418..6cf02a649 100644
--- a/Eigen/src/Core/ProductBase.h
+++ b/Eigen/src/Core/ProductBase.h
@@ -154,7 +154,8 @@ class ProductBase : public MatrixBase<Derived>
 #else
       EIGEN_STATIC_ASSERT_SIZE_1x1(Derived)
       eigen_assert(this->rows() == 1 && this->cols() == 1);
-      return derived().coeff(row,col);
+      Matrix<Scalar,1,1> result = *this;
+      return result.coeff(row,col);
 #endif
     }
 
@@ -162,7 +163,8 @@ class ProductBase : public MatrixBase<Derived>
     {
       EIGEN_STATIC_ASSERT_SIZE_1x1(Derived)
       eigen_assert(this->rows() == 1 && this->cols() == 1);
-      return derived().coeff(i);
+      Matrix<Scalar,1,1> result = *this;
+      return result.coeff(i);
     }
 
     const Scalar& coeffRef(Index row, Index col) const
diff --git a/test/product_small.cpp b/test/product_small.cpp
index d7f1c09ff..cf430a2d3 100644
--- a/test/product_small.cpp
+++ b/test/product_small.cpp
@@ -25,6 +25,25 @@
 #define EIGEN_NO_STATIC_ASSERT
 #include "product.h"
 
+// regression test for bug 447
+void product1x1()
+{
+  Matrix<float,1,3> matAstatic;
+  Matrix<float,3,1> matBstatic;
+  matAstatic.setRandom();
+  matBstatic.setRandom();
+  VERIFY_IS_APPROX( (matAstatic * matBstatic).coeff(0,0), 
+                    matAstatic.cwiseProduct(matBstatic.transpose()).sum() );
+
+  MatrixXf matAdynamic(1,3);
+  MatrixXf matBdynamic(3,1);
+  matAdynamic.setRandom();
+  matBdynamic.setRandom();
+  VERIFY_IS_APPROX( (matAdynamic * matBdynamic).coeff(0,0), 
+                    matAdynamic.cwiseProduct(matBdynamic.transpose()).sum() );
+}
+
+
 void test_product_small()
 {
   for(int i = 0; i < g_repeat; i++) {
@@ -33,6 +52,7 @@ void test_product_small()
     CALL_SUBTEST_3( product(Matrix3d()) );
     CALL_SUBTEST_4( product(Matrix4d()) );
     CALL_SUBTEST_5( product(Matrix4f()) );
+    CALL_SUBTEST_6( product1x1() );
   }
 
 #ifdef EIGEN_TEST_PART_6