libxml2 with C++ exception

[Philipp Kraus]

Hello,

I' using for XML parsing the libxml2 library and I use the native C
interface (not the C++ bindings). I parse a std::string with this code
const char* l_xmlcontent = p_xml.c_str();
xmlDocPtr l_xml = xmlParseMemory( l_xmlcontent,
strlen(l_xmlcontent) );

p_xml is a std::string. In some cases the XML data within the string
can't be valid and I get the correct message:
Entity: line 1: parser error : Start tag expected, '<' not found

The message is shown on the command line on each time, but I would like
to catch the error and would like to throw an exception. A try-catch
statement around the xmlParseMemory does not work. I've found some
notes that I can use a callback function, which is run on an error, but
I don't find any information for the implementation.

I hope my question isn't off-topic and anyonw can help me to create on
a parser error a correct exception

Thanks

Phil

 

[Michael DOUBEZ]

I' using for XML parsing the libxml2 library and I use the native C
interface (not the C++ bindings). I parse a std::string with this code
        const char* l_xmlcontent = p_xml.c_str();
        xmlDocPtr l_xml          = xmlParseMemory( l_xmlcontent,
strlen(l_xmlcontent) );

p_xml is a std::string. In some cases the XML data within the string
can't be valid and I get the correct message:
Entity: line 1: parser error : Start tag expected, '<' not found

The message is shown on the command line on each time, but I would like
to catch the error and would like to throw an exception.

Catching the error is easy: libxml2 let you define the error handlers:
see the xml*ErrorFunc() functions in the API.

A try-catch
statement around the xmlParseMemory does not work. I've found some
notes that I can use a callback function, which is run on an error, but
I don't find any information for the implementation.

*BUT* propagating an exception through C code is a bad idea. The
libxml2 doesn't expect to loose flow for control and leaks are likely
to occur. The proper solution is to build a C++ wrapper that stores
errors and throw them upon error return code (you can use
xmlCtxtGetLastError/xmlGetLastError)

 

[Philipp Kraus]

Catching the error is easy: libxml2 let you define the error handlers:
see the xml*ErrorFunc() functions in the API.

oh thanks a lot

*BUT* propagating an exception through C code is a bad idea. The
libxml2 doesn't expect to loose flow for control and leaks are likely
to occur. The proper solution is to build a C++ wrapper that stores
errors and throw them upon error return code (you can use
xmlCtxtGetLastError/xmlGetLastError)

I do this for a special XML structure. Parsing XML, checking errors,
clearing all data and throwing an error if needed.