fdo#77027: add some comments to prevent such oversights

Change-Id: I381c9738bba3e422e01324fa0c781c857db3d360

include/xmloff/xmlimp.hxx

@@ -430,11 +430,18 @@ public:
     static const sal_uInt16 OOo_34x = 34;
     // for AOO, no release overlaps with OOo, so continue OOo version numbers
     static const sal_uInt16 AOO_40x = 40;
+    // @ATTENTION: it's not usually ok to use the "4x" "wildcard" in an "=="
+    // comparison, since that will match unreleased versions too; it is also
+    // risky to use it in "<" comparison, because it requires checking and
+    // possibly adapting all such uses when a new value for a more specific
+    // version is added.
     static const sal_uInt16 AOO_4x = 41;
     static const sal_uInt16 LO_flag = 0x100;
     static const sal_uInt16 LO_3x = 30 | LO_flag;
     static const sal_uInt16 LO_41x = 41 | LO_flag;
     static const sal_uInt16 LO_42x = 42 | LO_flag;
+    /// @ATTENTION: when adding a new value more specific than "4x", grep for
+    /// all current uses and adapt them!!!
     static const sal_uInt16 LO_4x = 43 | LO_flag;
     static const sal_uInt16 ProductVersionUnknown = SAL_MAX_UINT16;
 

xmloff/source/draw/XMLGraphicsDefaultStyle.cxx

@@ -125,6 +125,11 @@ void XMLGraphicsDefaultStyle::SetDefaults()
         xDefaults->setPropertyValue("IsFollowingTextFlow", uno::makeAny(true));
     }
 
+    // NOTE: the only reason why it's legal to check "==" (not "<") against
+    // arbitrary versions here is that the default value of these attributes
+    // is not defined by ODF, therefore it is implementation-defined
+    // (and we of course must not override any attributes that are actually
+    // in the document, so check for that)
     bool const bIsAOO4(
            GetImport().getGeneratorVersion() >= SvXMLImport::AOO_40x
         && GetImport().getGeneratorVersion() <= SvXMLImport::AOO_4x);