Size problem using zgeqrf and zunmqr

Hello,

After using zgeqrf to compute the QR factorization of an m by n matrix, I want to multiply Q by another matrix C (k by k with k<m) with zunmqr.

My problem is that the result of the multiplication overwrites the matrix C, which size is smaller than the expected result.

I expect to get an m by k matrix, but C is only allocated for a k by k size.

Is there a way to directly compute the product into another allocated matrix with the proper size, or is the only solution to first compute the matrix Q and then multiply with zgemm ?

Thanks a lot in advance for your response.

Pierre