Re: [Xen-devel] [PATCH v6 1/4] xen: introduce SYMBOL

[Stewart Hildebrand <Stewart.Hildebrand@xxxxxxxxxxxxxxx>]

On Friday, January 11, 2019 3:36 PM, Julien Grall wrote:
> On Fri, 11 Jan 2019, 12:53 Stewart Hildebrand wrote:
> >
> > Why don't we change the type of _start so it's not a pointer type?
>
> Can you suggest a type that would be suitable?
>
> Cheers,

Yes. My opinion is that the "sufficient-width integer type" should be a
"uintptr_t" or "intptr_t", since those types by definition are *integer* types
wide enough to hold a value converted from a void pointer. While "unsigned
long" seems to work for Linux, the definition of that type doesn't provide the
same guarantee. Since uintptr_t is an *integer* type by definition (and not a
pointer type), my interpretation of the C standard is that
subtraction/comparison of uintptr_t types won't be subject to the potential
"pointer to object" issues in question.

If I had to choose between "uintptr_t" or "intptr_t" I guess I would choose
"uintptr_t" since that type is already used in various places in the Xen
codebase. And the Linux workaround is also using an unsigned integer type.

Stew
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