At 08:47 AM 4/17/2008 -0400, Greg A. Woods; Planix, Inc. wrote:
However what you and Alan said about simply casting to (unsigned char) isn't sufficient, at least on some platforms (IRIX-6, IIRC), at least not to keep the compiler happy. Sadly I do get the least warnings from every platform when the cast is only to (int). I wonder if the compiler can be taught to detect uses where a parameter may have a value out of range even though the data type it is declared as is wide enough. The only solution the compiler can really believe though, I think, would be a double cast where the value is narrowed sufficiently before being widened again for the call.
Hmm. Back in the bad old days before C-89, casts didn't portably guarantee that the result of casting was any different than what you started with. So for example isspace((uchar) x) could be wrong if x was > 0xFF.
I remember that the recommended practice (when using Whitesmiths C) was instead:
isspace(x & 255)
I think thks probably still works -- a smart compiler should be able
to do the modulo 256 reduction without actually masking, on most
platforms. In any event, when using modern compilers, the '&' will
make everything an int, and shouldn't cause any warnings. (Of
course, the usual #defines and so forth would normally be used
instead of writing '255'....) Also, it avoids a cast, which normally
is better.
Best regards, --Terry