Re: More information about inline function "used but never defined" error?

[Paul Pluzhnikov]

john.pye@gmail.com (John Pye) writes:

>     // only defined for unitless types

   template <> // missing, required: 
               // units.h:104: error: explicit specialization of 
               // `Units<0, 0, 0, 0, 0>::operator double() const' must be 
introduced by `template <>'

>     inline Units<0,0,0,0,0>::operator double() const {
>       return d_val;
>     }

FWIW, your code compiles cleanly with gcc-3.2, 3.4.0, 3.4.3 and
(after the fix above) gcc-4.0-20040919.

It does not however link with any of them:
/tmp/ccONzY0L.o: In function `main':
/tmp/ccONzY0L.o(.text+0x62): undefined reference to `Units<0, 0, 0, 1, 
0>::operator double() const'

> I would like to get some more information from the compiler about
> where this call is coming from, rather than just where the definition
> is lacking.

Well, the message above says the call is coming from 'main()',
and it is quite clear that it is coming from this line:

    double upsilon = T + 13.5 / (T - 23.5);

which can be alternatively written as (and is translated by the
compiler as):

    double upsilon = (double)T + (13.5 / ((double)T - 23.5)); // or
    double upsilon = T.operator double() + (13.5 / (T.operator double() - 
23.5));

Cheers,
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