Avoid -fsanitize=float-cast-overflow

...as happens when loading xhtml/kde143045-4.xhtml as obtained via
bin/get-bugzilla-attachments-by-mimetype (i.e., the attachment at
<https://bugs.kde.org/show_bug.cgi?id=143045#c4>):

> sw/source/filter/html/svxcss1.cxx:1424:60: runtime error: -5000 is outside the range of representable values of type 'unsigned long'
>  #0 in ParseCSS1_background(CSS1Expression const*, SfxItemSet&, SvxCSS1PropertyInfo&, SvxCSS1Parser const&) at sw/source/filter/html/svxcss1.cxx:1424:60
>  #1 in SvxCSS1Parser::DeclarationParsed(rtl::OUString const&, std::unique_ptr<CSS1Expression, std::default_delete<CSS1Expression> >) at sw/source/filter/html/svxcss1.cxx:3156:9
>  #2 in CSS1Parser::ParseRule() at sw/source/filter/html/parcss1.cxx:774:5
>  #3 in CSS1Parser::ParseStyleSheet() at sw/source/filter/html/parcss1.cxx:719:13

Conversion to integral type (which truncates) was always there at least since
7b0b5cdfeed656b279bc32cd929630d5fc25878b "initial import".  It is unclear to me
whether that's really relevant or wanted, but lets keep that behavior with an
explicit std::trunc.

Change-Id: Ib3b99a89e460850a992b403982e2797d24eee65b
Reviewed-on: https://gerrit.libreoffice.org/73980
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/sw/source/filter/html/svxcss1.cxx b/sw/source/filter/html/svxcss1.cxx
index b956bb401a9e..c1ecd4315b16 100644
--- a/sw/source/filter/html/svxcss1.cxx
+++ b/sw/source/filter/html/svxcss1.cxx
@@ -17,6 +17,9 @@
  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  */
 
+#include <sal/config.h>
+
+#include <cmath>
 #include <memory>
 #include <stdlib.h>
 
@@ -1421,15 +1424,15 @@ static void ParseCSS1_background( const CSS1Expression *pExpr,
                 // only distinguish between 0 and !0. Therefore pixel
                 // can be handled like all other units.
 
-                sal_uLong nLength = static_cast<sal_uLong>(pExpr->GetNumber());
+                bool nonZero = std::trunc(pExpr->GetNumber()) != 0.0;
                 if( !bHori )
                 {
-                    ePos = nLength ? GPOS_MM : GPOS_LT;
+                    ePos = nonZero ? GPOS_MM : GPOS_LT;
                     bHori = true;
                 }
                 else if( !bVert )
                 {
-                    MergeVert( ePos, (nLength ? GPOS_LM : GPOS_LT) );
+                    MergeVert( ePos, (nonZero ? GPOS_LM : GPOS_LT) );
                     bVert = true;
                 }
             }