From d0d76a9aad90c8f07330da7f67eef5c607a27aec Mon Sep 17 00:00:00 2001
From: Eike Rathke <erack@redhat.com>
Date: Thu, 13 Aug 2015 22:03:53 +0200
Subject: add sc::divide() for defined -fsanitize=float-divide-by-zero behavior

Change-Id: I3af85344119ca0056a127a5278e8993f9d79e2f9
---
 sc/inc/math.hxx | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

(limited to 'sc/inc')

diff --git a/sc/inc/math.hxx b/sc/inc/math.hxx
index 8a95f219d8fd..46f9a1d30fca 100644
--- a/sc/inc/math.hxx
+++ b/sc/inc/math.hxx
@@ -24,12 +24,41 @@
 
 namespace sc {
 
+/** Return fNumerator/fDenominator if fDenominator!=0 else #DIV/0! error coded
+    into double.
+ */
 inline double div( const double& fNumerator, const double& fDenominator )
 {
     return (fDenominator != 0.0) ? (fNumerator / fDenominator) :
         CreateDoubleError( errDivisionByZero);
 }
 
+/** Return fNumerator/fDenominator if fDenominator!=0 else +-Infinity if
+    fNumerator!=0 or NaN if fNumerator==0.
+
+    This allows to build/run with -fsanitize=float-divide-by-zero and have a
+    defined behavior for the otherwise undefined division by zero case ("If the
+    second operand of / or % is zero the behavior is undefined."
+    ([expr.mul]/4)).
+
+    The Calc interpreter gracefully handles Infinity or NaN double values
+    encountered as interim or final results, using this function we can ensure
+    defined behavior where desired.
+
+    Use where the double coded error creating div() is not wanted.
+ */
+inline double divide( const double& fNumerator, const double& fDenominator )
+{
+    if (fDenominator == 0.0) {
+        if (std::isfinite(fNumerator) && fNumerator != 0.0) {
+            return std::copysign(INFINITY, fNumerator);
+        } else {
+            return NAN;
+        }
+    }
+    return fNumerator / fDenominator;
+}
+
 }
 
 #endif
-- 
cgit