implement Inf and NaN handling for rtl_math_expm1() and rtl_math_log1p()

Change-Id: Ie424a6f038107ef8b574d0422efaf49b441c110f

1 files changed, 43 insertions, 0 deletions

diff --git a/sal/rtl/math.cxx b/sal/rtl/math.cxx
index 37225f4c7b46..3ec6fe0d489d 100644
--- a/sal/rtl/math.cxx
+++ b/sal/rtl/math.cxx
@@ -1096,6 +1096,24 @@ double SAL_CALL rtl_math_approxValue( double fValue ) SAL_THROW_EXTERN_C()
 
 double SAL_CALL rtl_math_expm1( double fValue ) SAL_THROW_EXTERN_C()
 {
+    // See http://en.cppreference.com/w/cpp/numeric/math/expm1
+
+    if (fValue == 0.0)
+        return fValue;
+
+    if (!::rtl::math::isFinite(fValue))
+    {
+        if (::rtl::math::isInf(fValue))
+        {
+            if (::rtl::math::isSignBitSet(fValue))
+                return -1.0;
+            else
+                return fValue;
+        }
+        // It is a NaN.
+        return fValue;
+    }
+
     double fe = exp( fValue );
     if (fe == 1.0)
         return fValue;
@@ -1106,6 +1124,31 @@ double SAL_CALL rtl_math_expm1( double fValue ) SAL_THROW_EXTERN_C()
 
 double SAL_CALL rtl_math_log1p( double fValue ) SAL_THROW_EXTERN_C()
 {
+    // See http://en.cppreference.com/w/cpp/numeric/math/log1p
+
+    if (fValue == 0.0)
+        return fValue;
+
+    if (fValue == -1.0)
+    {
+        rtl::math::setInf( &fValue, true);
+        return fValue;
+    }
+
+    if (fValue < -1.0)  // includes -Inf
+    {
+        rtl::math::setNan( &fValue);
+        return fValue;
+    }
+
+    if (!::rtl::math::isFinite(fValue))
+    {
+        if (::rtl::math::isInf(fValue))
+            return fValue;
+        // It is a NaN.
+        return fValue;
+    }
+
     // Use volatile because a compiler may be too smart "optimizing" the
     // condition such that in certain cases the else path was called even if
     // (fp==1.0) was true, where the term (fp-1.0) then resulted in 0.0 and