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From:   =?UTF-8?Q?Maciej_=C5=BBenczykowski?= <maze@google.com>
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Subject: Re: [PATCH iproute2] tc: fix warning in q_pie.c
To:     Stephen Hemminger <stephen@networkplumber.org>
Cc:     Brian Vazquez <brianvv@google.com>,
        Brian Vazquez <brianvv.kernel@gmail.com>,
        David Ahern <dsahern@gmail.com>,
        Mahesh Bandewar <maheshb@google.com>,
        Linux NetDev <netdev@vger.kernel.org>,
        Leslie Monis <lesliemonis@gmail.com>
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> What compiler is this?
> The type seems correct already.  The type of double / unsigned long is double.
> And the conversion may give different answer.

Probably some recent version of clang with -Wall.

That said, I think the warning/error is correct.
UINT64 doesn't fit in double (which is also 64 bits, but includes sign
and exponent) - you lose ~13 bits of precision.
I'm not aware of a way to (natively) divide a double by a uint64
without the loss (not that it really matters since the double doesn't
have the requisite precision in the first place).

Why do you think the conversion will give a different answer?
Isn't this exactly what the compiler will do anyway?
It's not like we have long double anymore...