[Lapack] obtaining size of work array

[Sorkin Dima]

Hi.
  Many Lapack subroutines ( I especially interested in gels ),
calculate and return the optimal size of work array when the argument 
LWORK is  -1 .

Question: When I query the optimal workspace size this way,
may I supply the matrix A and the vector B arguments as null pointers
(but supplying the sizes M, N, LDA, LDB right, sizes of actual matrices
on which I will apply the subroutine after allocating work array) ?

Thank you. Regards.
  Dima.