ofz#3819 Integer-overflow

Change-Id: Ic45692152b039c0ee2f5659d7739c3a2517c5e83
Reviewed-on: https://gerrit.libreoffice.org/43876Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

emfio/source/reader/mtftools.cxx

@@ -514,8 +514,9 @@ namespace emfio
         // must later be made portable in SV (KA 1996-02-08)
         Size  aFontSize = ImplMap (rFont.GetFontSize(), false);
 
-        if( aFontSize.Height() < 0 )
-            aFontSize.Height() *= -1;
+        const auto nHeight = aFontSize.Height();
+        if (nHeight < 0)
+            aFontSize.Height() = o3tl::saturating_toggle_sign(nHeight);
 
         rFont.SetFontSize( aFontSize );
 

include/o3tl/safeint.hxx

@@ -56,6 +56,15 @@ typename std::enable_if<std::is_unsigned<T>::value, T>::type saturating_add(
     }
 }
 
+template<typename T> inline
+typename std::enable_if<std::is_signed<T>::value, T>::type saturating_toggle_sign(
+    T a)
+{
+    if (a == std::numeric_limits<T>::min())
+        return std::numeric_limits<T>::max();
+    return a * -1;
+}
+
 #if defined(_MSC_VER)
 
 template<typename T> inline bool checked_multiply(T a, T b, T& result)