On 30/09/18 19:44, sundaresh wrote: > Why do struct's take up a lot more memory than the sum of the sizes of its > members ? This increases by even a lot more the larger the struct gets . If > the compiler is doing padding or aligning I would like to disable and not > have that at all since it is unnecessarily wasteful of memory ? I > encountered a similar problem when declaring floating point variables > independently outside a struct. The problem becomes worse if these floating > point variables are struct members. > A useful gcc flag here is "-Wpadded" - it will warn you if the compiler has had to add padding in a struct to make the alignments fit. This should show you where the wasted space is, and then you can try to re-arrange your struct's fields to get a more efficient fit. It is also possible to use the "packed" __attribute__ for structs which skips the spaces, but that makes the struct incompatible with external code and leads to inefficient unaligned accesses.
