Action review comments replacing fenv manipulation

Author: mborland

include/boost/math/distributions/logistic.hpp

@@ -148,10 +148,6 @@ namespace boost { namespace math {
        }
        BOOST_MATH_STD_USING
        RealType power = (location - x) / scale;
-       if(power > tools::log_max_value<RealType>())
-          return 0;
-       if(power < -tools::log_max_value<RealType>())
-          return 1;
        return logistic_sigmoid(-power, Policy());
     }
 
@@ -255,10 +251,6 @@ namespace boost { namespace math {
           return result;
        }
        RealType power = (x - location) / scale;
-       if(power > tools::log_max_value<RealType>())
-          return 0;
-       if(power < -tools::log_max_value<RealType>())
-          return 1;
        return logistic_sigmoid(-power, Policy());
     } 
 

include/boost/math/special_functions/logistic_sigmoid.hpp

@@ -8,8 +8,8 @@
 #define BOOST_MATH_SF_EXPIT_HPP
 
 #include <boost/math/policies/policy.hpp>
+#include <boost/math/tools/precision.hpp>
 #include <cmath>
-#include <cfenv>
 
 namespace boost {
 namespace math {
@@ -21,17 +21,16 @@ RealType logistic_sigmoid(RealType x, const Policy&)
 
     using promoted_real_type = typename policies::evaluation<RealType, Policy>::type;
 
-    #ifndef BOOST_MATH_HAS_GPU_SUPPORT
-    std::fexcept_t flags;
-    std::fegetexceptflag(&flags, FE_ALL_EXCEPT);
-    #endif
+    if(-x >= tools::log_max_value<RealType>())
+    {
+        return 0;
+    }
+    if(-x <= -tools::log_max_value<RealType>())
+    {
+        return 1;
+    }
 
     const auto res {static_cast<RealType>(1 / (1 + exp(static_cast<promoted_real_type>(-x))))};
-
-    #ifndef BOOST_MATH_HAS_GPU_SUPPORT
-    std::fesetexceptflag(&flags, FE_ALL_EXCEPT);
-    #endif
-
     return res;
 }
 

include/boost/math/special_functions/logit.hpp

@@ -9,6 +9,7 @@
 
 #include <boost/math/tools/config.hpp>
 #include <boost/math/policies/policy.hpp>
+#include <boost/math/policies/error_handling.hpp>
 #include <cmath>
 #include <cfenv>
 
@@ -23,10 +24,10 @@ RealType logit(RealType p, const Policy&)
 
     using promoted_real_type = typename policies::evaluation<RealType, Policy>::type;
 
-    #ifndef BOOST_MATH_HAS_GPU_SUPPORT
-    std::fexcept_t flags;
-    std::fegetexceptflag(&flags, FE_ALL_EXCEPT);
-    #endif
+    if (p < tools::min_value<RealType>())
+    {
+        return -policies::raise_overflow_error<RealType>("logit", "sub-normals will overflow ln(x/(1-x))", Policy());
+    }
 
     static const RealType crossover {RealType{1}/4};
     const auto promoted_p {static_cast<promoted_real_type>(p)};
@@ -40,10 +41,6 @@ RealType logit(RealType p, const Policy&)
         result = static_cast<RealType>(log(promoted_p / (1 - promoted_p)));
     }
 
-    #ifndef BOOST_MATH_HAS_GPU_SUPPORT
-    std::fesetexceptflag(&flags, FE_ALL_EXCEPT);
-    #endif
-
     return result;
 }
 

test/test_logistic_sigmoid.cpp

@@ -9,6 +9,7 @@
 #include "math_unit_test.hpp"
 #include <array>
 #include <cfloat>
+#include <cfenv>
 
 #pragma STDC FENV_ACCESS ON
 

test/test_logit.cpp

@@ -8,7 +8,8 @@
 #include <boost/multiprecision/cpp_bin_float.hpp>
 #include "math_unit_test.hpp"
 #include <array>
-#include <cfloat>
+#include <limits>
+#include <cfenv>
 
 #pragma STDC FENV_ACCESS ON
 
@@ -67,6 +68,25 @@ void test()
 
         CHECK_EQUAL(fe, false);
     }
+
+    #if defined(_CPPUNWIND) || defined(__EXCEPTIONS)
+
+    BOOST_MATH_IF_CONSTEXPR (std::is_arithmetic<RealType>::value)
+    {
+        bool thrown {false};
+        try
+        {
+            boost::math::logit(std::numeric_limits<RealType>::denorm_min());
+        }
+        catch (...)
+        {
+            thrown = true;
+        }
+
+        CHECK_EQUAL(thrown, true);
+    }
+
+    #endif // Exceptional environments
 }
 
 int main()