In Dtrsm, there is a check for the size of A (currently lines 2831 - 2839 of blas.go in cblas). The check tests assuming that A is an nxm or mxn matrix, but A is always symmetric. If on the left it is an M x M matrix ( {MxM} * {MxN} = {MxN}), and when on the right it is an NxN matrix.
In Dtrsm, there is a check for the size of A (currently lines 2831 - 2839 of blas.go in cblas). The check tests assuming that A is an nxm or mxn matrix, but A is always symmetric. If on the left it is an M x M matrix ( {MxM} * {MxN} = {MxN}), and when on the right it is an NxN matrix.