The functions for allocating memory to a block follow the style of
free. In addition they also perform their own
error checking. If there is insufficient memory available to allocate a
block then the functions call the GSL error handler (with an error
GSL_ENOMEM) in addition to returning a null
pointer. Thus if you use the library error handler to abort your program
then it isn't necessary to check every
gsl_block_callocif you want to ensure that all the elements are initialized to zero.
A null pointer is returned if insufficient memory is available to create the block.