On 01/08/2014 03:59 AM, Jonathan Wakely wrote:
The member def_value has no storage, so you can't initialize it. To
use it you need to allocate sizeof(struct foo_opt)+sizeof(x) where x
is the value you want def_val to have, and when you access def_val you
will be accessing the extra sizeof(x) bytes after the struct.
I don't see how you can statically initialize a foo_opt when you don't
know sizeof(x).
Here's a very simplified example for the specific case of a 16-bit short
on a little-endian system:
#define SHORT_BYTES(s) { ((s) & 0xff), (((s) >> 8) & 0xff) }
struct foo {
size_t value_size;
unsigned char value[];
};
static struct foo foo_short = {
.value_size = sizeof(short),
.value = SHORT_BYTES(513),
};
Ideally I could create some sort of generic macro that "casts" (using
the term very loosely) any static initializer to an array of unsigned
char that contains its binary representation. Sadly, I don't think
that's actually possible.
I don't supposed that gcc provides any facility that will allow the
pre-processor to determine endianness and/or type sizes?
--
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Ian Pilcher arequipeno@xxxxxxxxx
"If you're going to shift my paradigm ... at least buy me dinner first."
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