Hi,

I have the following piece of code. I was expecting a run-time error but did not get it. I was wondering if anyone has any inputs.

typedef Eigen::Matrix<double,6,6> Matrix6d;
Matrix6d P;
P << 10, 0, 0, 0, 0, 0,
0, 10, 0, 0, 1, 0,
0, 0, 10, 0, 0, 0,
0, 0, 0, 1, 0, 0,
0, 1, 0, 0, 1, 0,
0, 0, 0, 0, 0, 1;
Eigen::internal::set_is_malloc_allowed(false);
P = P*P;
Eigen::internal::set_is_malloc_allowed(true);

My understanding is that P=P*P requires the creation of a temporary variable. I thought the temporary variable will be dynamically allocated on the heap. Hence I was expecting an error. Or is Eigen creating the temporary variable on the stack?

I appreciate any inputs. Thanks !

ps: I have defined the macro EIGEN_RUNTIME_NO_MALLOC in my code

Fixed-size matrices are created on the stack. If you use a dynamic-size matrix (MatrixXd), you do get a run-time error.