RE: [PATCH net-next 09/10] net/mlx4_en: Manage flow steering rules with ethtool

"David Laight" [off-list ref] writes:

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Or write it as (!field || !(typeof(field))~field) which more

closely

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resembles what the macro name expresses.

Better still, or maybe:

	field == 0 || field == (typeof field)~0

Which doesn't work when sizeof(field) > sizeof(int).
Needs another cast.

	field == 0 || field == (typeof field)~(typeof field)0

You can avoid that by using (typeof field)-1.

Gah, I thought I knew the integral promotion rules!
-1 and ~0 are both 'integer' and get treated the same.

A quick test shows that gcc does sign extend when converting
32bit int to 64bit unsigned long long.
Which probably means that is required by the standard!

	David