[LLVMbugs] [Bug 21628] New: Increase limit of parameters in variadic template packs?

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=21628

            Bug ID: 21628
           Summary: Increase limit of parameters in variadic template
                    packs?
           Product: clang
           Version: 3.5
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++11
          Assignee: unassignedclangbugs at nondot.org
          Reporter: dimanne at ya.ru
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

template <class TUndInt, class TV>
constexpr TUndInt CalcMax(TV V) noexcept { return static_cast<TUndInt>(V); }

template <class TUndInt, class TV, class ...TVs>
constexpr TUndInt CalcMax(TV V, TVs... Vs) noexcept {
    return static_cast<TUndInt>(V) > CalcMax<TUndInt>(Vs...) ?
static_cast<TUndInt>(V) : CalcMax<TUndInt>(Vs...);
}

template <class TVs, TVs... Vs>
class TClass {
   static const auto MaxNotInc = CalcMax<TVs>(Vs...) + 1;
};

int main() {
   TClass<int, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
            , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
                                                                  >  Object;
   return 0;
}



If you shall try to compile above example, you get following error message:

$ clang++ --std=c++11 main.cpp 
main.cpp:2:42: error: in-class initializer for static data member is not a
constant expression
constexpr TUndInt CalcMax(TV V) noexcept { return static_cast<TUndInt>(V); }
                                         ^
main.cpp:17:70: note: in instantiation of template class
      'TClass<int, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24>' requested here
                                                                  >  Object;
                                                                     ^
1 error generated.

but it you decrease number of parameters by commenting out this line
, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
all works well.



$ clang++ --version
Ubuntu clang version 3.5.0-4ubuntu2 (tags/RELEASE_350/final) (based on LLVM
3.5.0)
Target: x86_64-pc-linux-gnu
Thread model: posix

$ uname -a
Linux DimanNeYa 3.16.0-24-generic #32-Ubuntu SMP Tue Oct 28 13:07:32 UTC 2014
x86_64 x86_64 x86_64 GNU/Linux

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20141121/b9142cfa/attachment.html>