🚀 go-pugleaf

Stephen Baynes wrote:
> 
> In a glossy newsletter from a company (who had better remain nameless) that
> sells tools for testing and validating C code the following bit of code was
> given as an example of implementation dependent but portable code across ISO
> C implementations. I know 'portable' is not a term used in the standard

Correct.

, let
> us assume it means conforming.

Bad choice. The term "conforming", when applied to user code (not to
implementations) is virtually meaningless. The U.S. Constitution is a
conforming piece of C code, or at least could be, given the existence of
a hypothetical compiler which makes it so.

I suspect the intended characteristic here is one that has been
informally dubbed "strongly conforming", meaning it violates no syntax
rule or semantic constraint, and does not invoke undefined behavior.

> Is this program conforming, giving an
> implementation defined result (regardless of the fact the result is probably
> not the one intended) or is it going to give undefined behaviour?
> 
> 
> #include <stdio.h>
> #include <limits.h>
> int main( void )
> {
>     printf( "%d", UINT_MAX );
>     return 0;
> }
> 
> My vote is for undefined, but can anyone construct an argument based on
> the represention of integers that makes it implmentation defined?

Well, my vote is for implementation-defined, or at worst, unspecified,
but I can be convinced otherwise. Ints and unsigned-ints are required to
be the same size, I believe, and so the  result should depend only on
the interpretation of the UINT_MAX bit pattern as a signed int.

My gut feeling is that there's no reason why a reasonable implementation
should crash from the above code.

--

Chris Volpe				Phone: (518) 387-7766 (Dial Comm 8*833
GE Corporate R&D			Fax:   (518) 387-6560
PO Box 8, Schenectady, NY 12301		Email: volpecr@crd.ge.com