🚀 go-pugleaf

clamage@Eng (Steve Clamage) writes:

>tony@online.tmx.com.au (Tony Cook) writes:
>
>>Steve Clamage (clamage@Eng) wrote:
>
>>: In the mean time, you could write a specialization of Foo<X>::compare
>>: that throws an exception or invokes "assert(0)" to allow your code
>>: to compile and link. That is, for example, if you use Foo<complex>,
>>: you could provide the specialization
>>: 	int Foo<complex>::compare(const complex&) { assert(0); return 0; }
>>: which will prevent the compiler from generating a version from the template,
>>: and will thus allow your program to compile and link.
>
>>Can we instead _declare_ the specialization and not define it:
>
>>    extern int Foo<complex>::compare(const complex &);
>
>>So that we see an error at link time rather than run-time?
>
>No. The declaration does not prevent instantiation if any use is made
>of the function. That is, the declaration tells the compiler that
>particular compare function is supposed to exist. If it is needed
>but not found at link time, the system will generate it from the
>template definition.

(I'm sorry to jump in late.)
Sorry, I don't think this is right.   As I understand it, declaring
a specialization before every place it is used *does* prevent 
automatic instantiation.   It's a violation of ODR (not required
to be detected) if you miss declaring it first, though, in one or 
more places.

Nathan Myers
myersn@roguewave.com

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