gcc bitfield order control

[Jon Grant <jg at jguk dot org>]

Hello

I have a build with a lot of structures in a big-endian style layout.
[I recognise that bit-fields are not portable due to their ordering
not being locally MSB first like the regular bit shift operation <<
is.    i.e.    (1<<2) == 4   ]


typedef struct reg32 {
	union  {
		_uint32 REG32;
		struct {
			_uint32 BIT31:1;
			_uint32 BIT30:1;
			_uint32 BITS:30;
		} B;
	} R;
} reg32_t;


On a little-endian ARM build. Using :

arm-none-eabi-gcc (Sourcery G++ Lite 2010.09-51) 4.5.1


Writing reg.R.REG32 = 1, results in BIT31 containing 1. Rather than
the "1" being in the "BITS" field.

My thought is I'll need to swap every structure to be in little-endian
style ordering. Does anyone have any other ideas how to handle this
with gcc?

I was thinking to write a little program to make the changes to the header file.

Please include my email address in any replies.

Best regards, Jon