Resolves: tdf#156985 Treat adding two KahanSum differently

When summing mixed formula cells and numeric cells, cell type runs are
summed using KahanSum that when switching cell types are added. Using
add() to explicitly add the rhs m_fError compensation value separately
may had lead to effectively cancelling out the relation of sum and
error, living on with an unrelated error value. Instead, add a "final"
rhs sum+compensation.

Change-Id: I751d3e0eeef9cd80482895c24f05b1ab667c3020
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/156253
Tested-by: Jenkins
Reviewed-by: Eike Rathke <erack@redhat.com>
(cherry picked from commit caafee1a4805e40d29be5c90f3a021ed6ef5c4d2)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/156431
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>
(cherry picked from commit 3cb3b713e1f3b8abe8d9bb46c89f58c7efdf8196)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/156444
Reviewed-by: Ilmari Lauhakangas <ilmari.lauhakangas@libreoffice.org>
Reviewed-by: Hossein <hossein@libreoffice.org>
Tested-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/sc/inc/kahan.hxx b/sc/inc/kahan.hxx
index 6c84f6eeef2e..ac97ae4394fa 100644
--- a/sc/inc/kahan.hxx
+++ b/sc/inc/kahan.hxx
@@ -71,8 +71,15 @@ public:
       */
     inline void add(const KahanSum& fSum)
     {
+#ifdef _WIN32
+        // For some odd unknown reason WIN32 fails badly with the
+        // sum+compensation value. Continue keeping the old though slightly off
+        // (see tdf#156985) explicit addition of the compensation value.
         add(fSum.m_fSum);
         add(fSum.m_fError);
+#else
+        add(fSum.m_fSum + fSum.m_fError);
+#endif
         add(fSum.m_fMem);
     }
 
@@ -82,8 +89,12 @@ public:
       */
     inline void subtract(const KahanSum& fSum)
     {
+#ifdef _WIN32
         add(-fSum.m_fSum);
         add(-fSum.m_fError);
+#else
+        add(-(fSum.m_fSum + fSum.m_fError));
+#endif
         add(-fSum.m_fMem);
     }