Array initialisation warning

Question

Hi, I'm trying to initialise a structure which ends with an array[0] (here, char iedata[0]) for the actual packet payload. If I try to initialise it inline, like this:

struct some_packet pkt = {
   .elem1 = blah, .elem2 = bleh,
   .iedata = {
      1, 2, 3, 4
   }
};

I get a warning from gcc:

warning: (near initialization for ‘pkt.iedata’)

Is there any good way to mark that this is a proper initialisation?

Answer 1

If you're able to compile in C99 mode, you could try using standard flexible length arrays rather than the zero-length hack: http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html

Note that in GCC 3.0 and newer, extra entries in an array initialiser will be discarded (per the documentation linked above).

Answer 2

As you are using C99 initialization, why not make the member a proper FAM, i.e. char data[];

The only way to create valid struct's with a FAM (or struct hack member) is by dynamically allocating the correct amount of excess storage for the last member so, as the warning suggests, your local initialization isn't valid.