[boost] interval library: bug fix

From: Jens Maurer (Jens.Maurer_at_[hidden])
Date: 2004-01-13 17:47:46

A compiler vendor contacted me because his x86 compiler
has sizeof(long double) == 8, so force_rounding cannot
be a no-op for the "long double" case.  (My name is at
the top of the x86_rounding_control.hpp file, so he
contacted me.)

I've checked in the following fix to the CVS main
branch.  Could the interval developers please verify
the correctness of the fix and, if correct, consider
forwarding the fix to the release branch?

Thanks.

Jens Maurer

diff -u -r1.6 x86_rounding_control.hpp
--- x86_rounding_control.hpp    30 May 2003 13:54:58 -0000      1.6
+++ x86_rounding_control.hpp    13 Jan 2004 22:39:52 -0000
@@ -82,7 +82,17 @@
  template<>
  struct rounding_control<long double>: detail::x86_rounding_control
  {
-  static const long double& force_rounding(const long double& r) { return r; }
+  static long double force_rounding(const long double& r)
+  {
+    // Some compilers use "double == long double", so we may need to
+    // round (from FPU registers into memory) in this case as well.
+    if(sizeof(long double) > 8) {
+      return r;
+    } else {
+      volatile long double r_ = r;
+      return r_;
+    }
+  }
  };

  } // namespace interval_lib