[U-Boot] [PATCH v2 07/13] x86: Fix signed shift overflow in MSR_IA32_APICBASE_BASE

[Andy Shevchenko]

On Tue, Aug 28, 2018 at 5:06 AM Bin Meng <bmeng.cn at gmail.com> wrote:
> On Mon, Aug 27, 2018 at 7:19 AM Eugeniu Rosca <roscaeugeniu at gmail.com> wrote:


> > -#define MSR_IA32_APICBASE_BASE         (0xfffff<<12)
> > +#define MSR_IA32_APICBASE_BASE         (0xfffffUL << 12)
>
> I don't understand why such warnings is emitted: "left shift of
> 1048575 by 12 places cannot be represented in type 'int'"

Because it can't.

1 << 30 (fine)
1 << 31 (UB!)

This is good explained in the C standard for ages.

> Compilers don't complain this code and Linux kernel has the same
> definition here.

Someone suppressed those warnings. But they are valid.

-- 
With Best Regards,
Andy Shevchenko