Re: [libvirt] [PATCH RFC 1/2] XML: Improve XML parsing error messages

This patch modifies error handling function for the XML parser provided by libxml2. Originaly only a line number and error message were logged. With this new error handler function, the user is provided with a more complex description of the parsing error. Context of the error is printed in libXML2 style and filename of the file, that caused the error is printed. Example of an parse error: 13:41:36.262: 16032: error : catchXMLError:706 : /etc/libvirt/qemu/rh_bad.xml:58: Opening and ending tag mismatch: name line 2 and domain </domain> ---------^ Context of the error gives the user hints that may help to quickly locate a corrupt xml file. fixes BZs: ---------- Bug 708735 - [RFE] Show column and line on XML parsing error https://bugzilla.redhat.com/show_bug.cgi?id=708735 Bug 726771 - libvirt does not specify problem file if persistent xml is invalid https://bugzilla.redhat.com/show_bug.cgi?id=726771 --- src/util/xml.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++------- 1 files changed, 76 insertions(+), 12 deletions(-) diff --git a/src/util/xml.c b/src/util/xml.c index d301af6..b0942da 100644 --- a/src/util/xml.c +++ b/src/util/xml.c @@ -633,28 +633,92 @@ virXPathNodeSet(const char *xpath, * catchXMLError: * * Called from SAX on parsing errors in the XML. + * + * This version is heavily based on xmlParserPrintFileContextInternal from libxml2. */ static void catchXMLError(void *ctx, const char *msg ATTRIBUTE_UNUSED, ...) { - int domcode = VIR_FROM_XML; xmlParserCtxtPtr ctxt = (xmlParserCtxtPtr) ctx; - if (ctxt) { - if (ctxt->_private) + const xmlChar *cur, *base; + unsigned int n, col; /* GCC warns if signed, because compared with sizeof() */ + int domcode = VIR_FROM_XML; + + virBuffer buf = VIR_BUFFER_INITIALIZER; + char *contextstr = NULL; + char *pointerstr = NULL; + + + /* conditions for error printing */ + if (!ctxt || + (virGetLastError() != NULL) || + ctxt->input == NULL || + ctxt->lastError.level != XML_ERR_FATAL || + ctxt->lastError.message == NULL) + return; + + if (ctxt->_private) domcode = ((struct virParserData *) ctxt->_private)->domcode; - if (virGetLastError() == NULL && - ctxt->lastError.level == XML_ERR_FATAL && - ctxt->lastError.message != NULL) { - virGenericReportError(domcode, VIR_ERR_XML_DETAIL, - _("at line %d: %s"), - ctxt->lastError.line, - ctxt->lastError.message); - } + + cur = ctxt->input->cur; + base = ctxt->input->base; + + /* skip backwards over any end-of-lines */ + while ((cur > base) && ((*(cur) == '\n') || (*(cur) == '\r'))) { + cur--; } -} + /* search backwards for beginning-of-line (to max buff size) */ + while ((cur > base) && (*(cur) != '\n') && (*(cur) != '\r')) + cur--; + if ((*(cur) == '\n') || (*(cur) == '\r')) cur++; + + /* calculate the error position in terms of the current position */ + col = ctxt->input->cur - cur; + + /* search forward for end-of-line (to max buff size) */ + /* copy selected text to our buffer */ + while ((*cur != 0) && (*(cur) != '\n') && (*(cur) != '\r')) { + virBufferAddChar(&buf, *cur++); + } + + /* create blank line with problem pointer */ + contextstr = virBufferContentAndReset(&buf); + + /* (leave buffer space for pointer + line terminator) */ + for (n = 0; (n<col) && (contextstr[n] != 0); n++) { + if (contextstr[n] == '\t') + virBufferAddChar(&buf, '\t'); + else + virBufferAddChar(&buf, '-'); + } + + virBufferAddChar(&buf, '^'); + + pointerstr = virBufferContentAndReset(&buf); + + if (ctxt->lastError.file) { + virGenericReportError(domcode, VIR_ERR_XML_DETAIL, + _("%s:%d: %s%s\n%s"), + ctxt->lastError.file, + ctxt->lastError.line, + ctxt->lastError.message, + contextstr, + pointerstr); + } else { + virGenericReportError(domcode, VIR_ERR_XML_DETAIL, + _("at line %d: %s%s\n%s"), + ctxt->lastError.line, + ctxt->lastError.message, + contextstr, + pointerstr); + } + + VIR_FREE(contextstr); + VIR_FREE(pointerstr); +}