[Llvm-bgq-discuss] Bug when using boost::numeic_cast

[Godenschwager, Christian]

Hi everyone!

First let me say a big thank you to all the people who have put some effort
into bgclang! It is just great to have clang available on the BG/Q platform.

While compiling and running our C++ code using bgclang I stumbled upon a
problem using boost::numeric_cast. The code

#include <iostream>
#include <boost/numeric/conversion/cast.hpp>

int main()
{
   long  l = 0;
   int i = boost::numeric_cast<int>( l );
   std::cout << l << " " << i << std::endl;
}

results in a negative underflow exception when compiling it with bgclang. I
investigated a bit and the minimal example I could come up with not using
boost is

#include <iostream>
#include <limits>

template< typename T >
class Dummy
{
public:
   static T lowest() { return std::numeric_limits<T>::min(); }
};

int main()
{
   std::cout <<  static_cast<long>( Dummy<int>::lowest() ) << std::endl;
   std::cout <<  static_cast<long>( Dummy<int>::lowest() ) -
static_cast<long>(1.0) << std::endl;
}


Which prints

2147483648
2147483647

but should print

-2147483648
-2147483649

The problem only occurs when using bgclang++11 while bgclang++ works fine.
Also removing the intermediate Dummy class or removing the second line in
the main function results in correct behavior. I could reproduce the wrong
behavior with versions r248407, r236977 and r232720 while r220548 works
fine. I tested on JUQUEEN.

Could anyone look into that?

All the best,

Christian

--
Dipl.-Inform. Christian Godenschwager
Universitaet Erlangen-Nuernberg
Lehrstuhl fuer Informatik 10 - Systemsimulation
Cauerstraße 11
D-91058 Erlangen
 
Tel:    +49 9131 85 67292
Fax:    +49 9131 85 28928
E-Mail: christian.godenschwager at fau.de


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