[Bug c++/81134] C++ partial template specialization issue

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81134

Jonathan Wakely  changed:

   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution|--- |INVALID

--- Comment #1 from Jonathan Wakely  ---
This is not a bug, the conditional expression using ?: instantiates both
branches, so although one branch uses the terminating case, the other one
doesn't.

You can make the code valid like this:

template 
struct GCD
{
   static const int value
 = std::conditional<(N>M), GCD, GCD>::type::value;
};

Or like this:

template 
struct GCD : std::conditional<(N>M), GCD, GCD>::type
{ };

[Bug c++/81134] C++ partial template specialization issue

[manish.baphna at citi dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81134

--- Comment #2 from Manish  ---
Thanx Jonathan. 

Your explanation explains behavior. I wonder if standard has some preference
dictated here?

[Bug c++/81134] C++ partial template specialization issue

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81134

--- Comment #3 from Jonathan Wakely  ---
The standard seems clear to me and GCC's behaviour is correct.

[Bug c++/81134] C++ partial template specialization issue

[manish.baphna at citi dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81134

--- Comment #4 from Manish  ---
Which section in particular you are referring?

I am looking at this doc, section 14.7 but couldn't find relevant point.
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3690.pdf

[Bug c++/81134] C++ partial template specialization issue

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81134

--- Comment #5 from Jonathan Wakely  ---
To determine the type of the conditional expression it's necessary to know the
types of both GCD::value and GCD::value, which requires
instantiating both of GCD and GCD, which triggers the infinite
recursion.