[cfe-dev] Additional instantiations of anonymous enum inside a template

[Pavel Morozkin]

On 13 October 2014 03:53, Richard Smith <richard at metafoo.co.uk> wrote:

> On Sun, Oct 12, 2014 at 3:29 AM, Pavel Morozkin <pavel.morozkin at gmail.com>
> wrote:
>
>> Hello cfe-dev group,
>>
>> Consider this template metaprogram:
>> template <unsigned N> struct fib { enum { value = fib<N-1>::value +
>> fib<N-2>::value}; };
>> template <> struct fib<1> { enum { value = 1 }; };
>> template <> struct fib<0> { enum { value = 0 }; };
>>
>> During compilation of 'fib<2>::value' (after finally getting memoized
>> result of instantiation of struct fib<0>) Clang «instantiates the anonymous
>> enum inside fib<0> and fib<1>» 129 times in sum.
>>
>
> That sounds like a bug. How are you observing it?
>

I debugged the metaprogram with use of Metashell tool.


>
> In case, when we use 'constexpr static auto' instead of 'enum', no
>> additional instantiations occurs. Why Clang performs additional
>> instantiations in the first case?
>>
>> Thank you,
>> Pavel
>>
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>>
>>
>
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