Help with GCC, please

[Sergei Organov]

leonp at plris.com writes:

> Hello, all.
> 
> I ask for pardon, as the question is not on RTEMS proper, but on the 
> rtems-GCC.
> May be somebody knows...:-(
> 
> I wrote:
> unsigned char* cp;
> .....
> if (cp[6] == (cp[0]+cp[1]+cp[2]+cp[3]+cp[4]+cp[5]))
> ....
> The comparison never becomes equal, as the assembler code generates such 
> commands that the result at the right side is unsigned long.

No, the result is unsigned int. You need:

 if (cp[6] == (unsigned char)(cp[0]+cp[1]+cp[2]+cp[3]+cp[4]+cp[5]))


> 
> Why?

Due to the C type promotion rules in expressions. Refer to C language
specs.

-- 
Sergei.