Enables and disables automatic reordering of top-level data items, for example global variables.
The compiler can save memory by eliminating wasted space between data items. However,
--data_reorder can break legacy code, if the code makes invalid
assumptions about ordering of data by the compiler.
The ISO C Standard does not guarantee data order, so you must try to avoid writing code that depends on any assumed ordering. If you require data ordering, place the data items into a structure.
The default is optimization-level dependent: