Re: [Libusb-devel] signed vs unsigned num_iso_packets

[Andreas S. <ma...@cy...>]

On Friday 29 May 2009 18:02:33 Daniel Drake wrote:
> In the interest of not changing API, my temptation is to to modify the
> code in those 2 last functions, to first check that the unsigned number
> can safely fit in a signed int, and then to cast it and use it. That
> would fix the warnings and not break API in any way. What do people think?
> Unfortunately those 2 functions are static inlines inside libusb.h.
> Actually, would casting an unsigned int to an int cause a new compiler
> warning to come up, even if I range check it first?
>
>
> Other options include:
>   - making a small API change to those 2 last functions to accept "int"
>   - making a bigger API change to unsigned everywhere

I think you can do this safely. It is a API change but it will not really 
break the API and it should still be ABI compatible.

Casting from int to unsigned int should be no problem. I think we have only 
positive numbers here. Casting from unsinged int to int is a problem cause the 
first bit is the signed bit. So a large number could be a negative number 
after the cast.

So it is safer to change to unsinged values.

This is just my opinion...

	-- andreas