[sane-devel] C undefined operations in sane-backends-1.0.7-beta1

[Tim Waugh]

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On Fri, Jan 25, 2002 at 12:27:03PM +0100, Jaeger, Gerhard wrote:

> Hi there,=20
>=20
> let's have a look at the warnings from the Plustek backend.
> The lines that produce the problem include the following statement:
>=20
> _SWAP(x,y)	(x)^=3D(y)^=3D(x)^=3D(y)
>=20
> So what? Where's the problem here?

I think the problem is that there are two assignments to x with no
intervening sequence point.  Although the expression (x)^=3D(y) is
_evaluated_ first, it doesn't mean that the resulting value is then
assigned to x before the result of the expression (y)^=3D(x)^=3D(y) is;
the compiler is free to do it the other way around.

Tim.
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