OK, thanks. Good to know. I'll go back and put a bookmark in my K&R :-)
On Thu, Oct 7, 2010 at 2:21 PM, Peter Bigot <[email protected]> wrote:
> Third time's the charm? It's been so long since I've dealt with K&R C I've
> forgotten the rules.
>
> The behavior is correct. char and short are upcast to int when no
> declaration is in scope. Integral types that are larger than int are left
> as is. That you're masking off all but the low byte does not change the
> type of the expression that's used as a parameter: it's a 32-bit int on a
> 16-bit microcontroller, and requires two registers to pass by value.
>
> No bug here. Either explicitly cast to int, or make sure there's a
> declaration in scope so the compiler knows what to do. I suggest the
> latter.
>
> Peter
>
> On Thu, Oct 7, 2010 at 7:26 AM, Kim Toms <[email protected]> wrote:
>
> > I had a function which took a byte argument and returned a byte. From
> > another file (compiled into a separate object), I called the function
> > without first declaring it. The calling function used an argument which
> > evaluated to uint32_t.
> >
> > In the called function, it looked for the argument in R15. In the
> calling
> > function, it left the low byte of the argument in R14.
> >
> > Declaring the called function fixed the problem. Here's an example:
> >
> > file1.c:
> > uint8_t bytefunc(uint8_t arg)
> > { ...
> > }
> >
> > file2.c:
> > extern uint8_t bytefunc(uint8_t); // this line required to make the ABI
> > generate the correct code
> >
> > main()
> > {
> > uint32_t i = 123456;
> > bytefunc(i & 0xFFL);
> > }
> >
> >
> >
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------------------------------------------------------------------------------
Beautiful is writing same markup. Internet Explorer 9 supports
standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3.
Spend less time writing and rewriting code and more time creating great
experiences on the web. Be a part of the beta today.
http://p.sf.net/sfu/beautyoftheweb
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