Rounding mode not restored when using save_state rounding struct on x64

[Aaron Balog <abalog@…>]

The rounding mode is not restored when using interval_lib's save_state rounding struct on x64 when an exception is thrown (Visual Studio 2013/2015). This can have critical impact on applications. All rounding will remain downward after catching the exception. This bug does not occur in Win32.

We've also reported this issue to Microsoft: ​https://connect.microsoft.com/VisualStudio/Feedback/Details/2487437

Boost Repro:

#include <boost/numeric/interval.hpp>

void test_interval_number::test_boost_rounding() {

try {

boost::numeric::interval<double>::traits_type::rounding rnd; rnd.downward();

throw 1;

} catch (...) {

}

unsigned int fpu_flags = 0; errno_t err;

err = _controlfp_s(&fpu_flags, 0, 0); assert(err == 0);

assert((fpu_flags & _MCW_RC) != _RC_DOWN);

}