extern(C) bool function type?

[Charles Hixson]

On 09/26/2013 12:19 PM, bearophile wrote:
> Charles Hixson:
>
>> Does anyone know:
>> If an extern(c) function is defined as returning a bool, does D 
>> handle the conversion automatically into true and false?  Should it 
>> be defined as returning  an int?  On a 64 bit machine?  Does this 
>> depend on the compiler used to compile the library? int32_t? int_64_t?
>>
>> Is this portable or non-portable?
>
> A D bool is a C99 uint8_t that has values just 0 or 1.
>
> If your uint8_t contains a value x > 1, in many cases this works, but 
> some D code relying on the standard values of a D boolean breaks (like 
> when you sum bool values in D, to count the true ones).
>
> D doesn't handle those conversions beside the narrowing or extension 
> of bit-width lengths.
>
> Bye,
> bearophile
>
It's a library function, that claims to return bool, but is a C 
function.  My suspicion is that the proper way to handle this is to say 
that it returns an int, or possibly an int32_t, i.e. to declare is as 
not returning a bool, even though the library says that that's what it 
returns.  But my computer is a 64 bit machine, and the code was compiled 
awhile ago, so I suspect it may really be returning an int32_t.

The problem is that if I guess wrong this will not dependably cause a 
problem.  (I had a hope that D would say "O, it's a C routine returning 
a bool, so I know how to deal with that", but that wasn't really my 
expectation.)

Yeah, if I were defining the function, I'd define it in a way that I 
know how to handle properly.  But I'm not, and the interface is for 
either C or C++.   I can choose between those two.

So... if C returns an int64_t and I declare it as an int32_t, will this 
cause problems?  What about if C returns an int32_t and I declare it as 
an int64_t?  Or *is* there a good way to handle this? (I think that 
there's an error code I could interrogate if I need to just ignore the 
result...but I don't know if I can do this in all cases.)

-- 
Charles Hixson