The <cxxUnionDefinitionFileLineStart> element specifies the beginning of the union definition.
The <cxxUnionDefinitionFileLineStart> element is defined within <cxxUnionAPIItemLocation>. It contains the line number that the union definition begins on. The element is empty but for the required attributes name and value. The attribute name must be set to "lineNumber". The attribute value is set to the line number where union definition begins.
<cxxUnionDefinitionFileLineStart name="lineNumber" value="58"/>