Re: need for packed attribute

[Mikael Pettersson]

On Fri, 6 Jan 2006 18:38:46 +0000, Russell King wrote:
>> is there any architecture for which packed is required in structures like this:
>> 
>> /* All standard descriptors have these 2 fields at the beginning */
>> struct usb_descriptor_header {
>> 	__u8  bLength;
>> 	__u8  bDescriptorType;
>> };
>
>sizeof(struct usb_descriptor_header) will be 4 on ARM.

I found this surprising, but gcc-3.4.5 for ARM seems to agree with you.

As fas as I can tell, the AAPCS document (v2.03 7th Oct 2005) requires
that a simple "struct foo { unsigned char c; };" should have both size
and alignment equal to 1, but gcc makes them both 4. Do you have any
information about why gcc is doing this on ARM/Linux? Is there an accurate
ABI document for ARM/Linux somewhere?

/Mikael
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/