From mboxrd@z Thu Jan  1 00:00:00 1970
From: Scott Wood <scottwood@freescale.com>
Date: Tue, 30 Mar 2010 17:39:31 -0500
Subject: [U-Boot] [PATCH] fix print_size printing fractional gigabyte
 numbers on 32-bit platforms
In-Reply-To: <4BB27C1B.8000301@freescale.com>
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	<4BB278F1.40705@freescale.com> <4BB27C1B.8000301@freescale.com>
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Timur Tabi wrote:
> Scott Wood wrote:
> 
>> It would make the 10 * (...) product 64-bit regardless of phys_size_t, 
>> without changing the function signature (overflow is an internal 
>> implementation detail).
> 
> You are right that (n * d) is evaluated as a 32-bit integer:
> 
> 	print_size(5905580032)= 6.35 GB
> 
> However, changing "10" to "10ULL" does not fix this. 

It's not supposed to.

There are two different overflows, 10*expr and n*d.

Today, 10*expr overflows and n*d doesn't.  With your patch, n*d 
overflows and 10*expr doesn't.

I was suggesting a simple way to fix 10*expr without other changes.

> I think this is because we are both expecting integer sizes to commute across arithmetic operations.  That is, I assumed that:
> 
> 	u64 - (u32 * u32) 
> 
> would be treated as 
> 
> 	u64 - ((u64)u32 * u32) 
> 
> And you assumed that 
> 
> 	u64 * (u32 - u32)
> 
> would be treated as
> 
> 	u64 * (u32 - (u64) u32)

I assumed no such thing.

What I assumed was that the n*d overflow only matters if phys_size_t is 
64-bit, because it should always be less than size.

-Scott