This option enables or 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.