[U-Boot] [PATCH] fix print_size printing fractional gigabyte numbers on 32-bit platforms

[Scott Wood <scottwood@freescale.com>]

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