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Mark Simonetti reported that libxslt sometimes crashes for him, and that swapping xslt_process's object-freeing calls around to do them in reverse order of creation seemed to fix it. I've not reproduced the crash, but valgrind clearly shows a reference to already-freed memory, which is consistent with the idea that shutdown of the xsltTransformContext is trying to reference the already-freed stylesheet or input document. With this patch, valgrind is no longer unhappy. I have an inquiry in to see if this is a libxslt bug or if we're just abusing the library; but even if it's a library bug, we'd want to adjust our code so it doesn't fail with unpatched libraries. Back-patch to all supported branches, because we've been doing this in the wrong(?) order for a long time.
257 lines
5.9 KiB
C
257 lines
5.9 KiB
C
/*
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* contrib/xml2/xslt_proc.c
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*
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* XSLT processing functions (requiring libxslt)
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*
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* John Gray, for Torchbox 2003-04-01
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*/
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#include "postgres.h"
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#include "executor/spi.h"
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#include "fmgr.h"
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#include "funcapi.h"
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#include "miscadmin.h"
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#include "utils/builtins.h"
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#include "utils/xml.h"
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#ifdef USE_LIBXSLT
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/* libxml includes */
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#include <libxml/xpath.h>
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#include <libxml/tree.h>
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#include <libxml/xmlmemory.h>
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/* libxslt includes */
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#include <libxslt/xslt.h>
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#include <libxslt/xsltInternals.h>
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#include <libxslt/security.h>
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#include <libxslt/transform.h>
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#include <libxslt/xsltutils.h>
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#endif /* USE_LIBXSLT */
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#ifdef USE_LIBXSLT
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/* declarations to come from xpath.c */
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extern PgXmlErrorContext *pgxml_parser_init(PgXmlStrictness strictness);
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/* local defs */
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static const char **parse_params(text *paramstr);
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#endif /* USE_LIBXSLT */
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PG_FUNCTION_INFO_V1(xslt_process);
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Datum
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xslt_process(PG_FUNCTION_ARGS)
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{
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#ifdef USE_LIBXSLT
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text *doct = PG_GETARG_TEXT_P(0);
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text *ssheet = PG_GETARG_TEXT_P(1);
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text *result;
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text *paramstr;
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const char **params;
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PgXmlErrorContext *xmlerrcxt;
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volatile xsltStylesheetPtr stylesheet = NULL;
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volatile xmlDocPtr doctree = NULL;
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volatile xmlDocPtr restree = NULL;
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volatile xsltSecurityPrefsPtr xslt_sec_prefs = NULL;
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volatile xsltTransformContextPtr xslt_ctxt = NULL;
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volatile int resstat = -1;
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xmlChar *resstr = NULL;
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int reslen = 0;
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if (fcinfo->nargs == 3)
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{
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paramstr = PG_GETARG_TEXT_P(2);
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params = parse_params(paramstr);
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}
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else
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{
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/* No parameters */
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params = (const char **) palloc(sizeof(char *));
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params[0] = NULL;
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}
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/* Setup parser */
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xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY);
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PG_TRY();
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{
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xmlDocPtr ssdoc;
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bool xslt_sec_prefs_error;
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/* Parse document */
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doctree = xmlParseMemory((char *) VARDATA(doct),
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VARSIZE(doct) - VARHDRSZ);
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if (doctree == NULL)
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xml_ereport(xmlerrcxt, ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
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"error parsing XML document");
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/* Same for stylesheet */
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ssdoc = xmlParseMemory((char *) VARDATA(ssheet),
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VARSIZE(ssheet) - VARHDRSZ);
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if (ssdoc == NULL)
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xml_ereport(xmlerrcxt, ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
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"error parsing stylesheet as XML document");
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/* After this call we need not free ssdoc separately */
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stylesheet = xsltParseStylesheetDoc(ssdoc);
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if (stylesheet == NULL)
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xml_ereport(xmlerrcxt, ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
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"failed to parse stylesheet");
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xslt_ctxt = xsltNewTransformContext(stylesheet, doctree);
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xslt_sec_prefs_error = false;
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if ((xslt_sec_prefs = xsltNewSecurityPrefs()) == NULL)
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xslt_sec_prefs_error = true;
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if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_READ_FILE,
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xsltSecurityForbid) != 0)
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xslt_sec_prefs_error = true;
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if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_WRITE_FILE,
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xsltSecurityForbid) != 0)
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xslt_sec_prefs_error = true;
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if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_CREATE_DIRECTORY,
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xsltSecurityForbid) != 0)
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xslt_sec_prefs_error = true;
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if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_READ_NETWORK,
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xsltSecurityForbid) != 0)
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xslt_sec_prefs_error = true;
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if (xsltSetSecurityPrefs(xslt_sec_prefs, XSLT_SECPREF_WRITE_NETWORK,
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xsltSecurityForbid) != 0)
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xslt_sec_prefs_error = true;
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if (xsltSetCtxtSecurityPrefs(xslt_sec_prefs, xslt_ctxt) != 0)
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xslt_sec_prefs_error = true;
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if (xslt_sec_prefs_error)
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ereport(ERROR,
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(errmsg("could not set libxslt security preferences")));
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restree = xsltApplyStylesheetUser(stylesheet, doctree, params,
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NULL, NULL, xslt_ctxt);
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if (restree == NULL)
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xml_ereport(xmlerrcxt, ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
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"failed to apply stylesheet");
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resstat = xsltSaveResultToString(&resstr, &reslen, restree, stylesheet);
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}
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PG_CATCH();
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{
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if (restree != NULL)
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xmlFreeDoc(restree);
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if (xslt_ctxt != NULL)
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xsltFreeTransformContext(xslt_ctxt);
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if (xslt_sec_prefs != NULL)
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xsltFreeSecurityPrefs(xslt_sec_prefs);
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if (stylesheet != NULL)
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xsltFreeStylesheet(stylesheet);
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if (doctree != NULL)
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xmlFreeDoc(doctree);
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xsltCleanupGlobals();
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pg_xml_done(xmlerrcxt, true);
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PG_RE_THROW();
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}
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PG_END_TRY();
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xmlFreeDoc(restree);
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xsltFreeTransformContext(xslt_ctxt);
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xsltFreeSecurityPrefs(xslt_sec_prefs);
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xsltFreeStylesheet(stylesheet);
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xmlFreeDoc(doctree);
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xsltCleanupGlobals();
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pg_xml_done(xmlerrcxt, false);
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/* XXX this is pretty dubious, really ought to throw error instead */
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if (resstat < 0)
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PG_RETURN_NULL();
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result = cstring_to_text_with_len((char *) resstr, reslen);
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if (resstr)
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xmlFree(resstr);
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PG_RETURN_TEXT_P(result);
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#else /* !USE_LIBXSLT */
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ereport(ERROR,
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
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errmsg("xslt_process() is not available without libxslt")));
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PG_RETURN_NULL();
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#endif /* USE_LIBXSLT */
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}
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#ifdef USE_LIBXSLT
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static const char **
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parse_params(text *paramstr)
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{
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char *pos;
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char *pstr;
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char *nvsep = "=";
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char *itsep = ",";
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const char **params;
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int max_params;
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int nparams;
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pstr = text_to_cstring(paramstr);
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max_params = 20; /* must be even! */
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params = (const char **) palloc((max_params + 1) * sizeof(char *));
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nparams = 0;
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pos = pstr;
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while (*pos != '\0')
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{
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if (nparams >= max_params)
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{
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max_params *= 2;
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params = (const char **) repalloc(params,
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(max_params + 1) * sizeof(char *));
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}
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params[nparams++] = pos;
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pos = strstr(pos, nvsep);
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if (pos != NULL)
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{
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*pos = '\0';
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pos++;
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}
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else
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{
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/* No equal sign, so ignore this "parameter" */
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nparams--;
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break;
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}
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/* since max_params is even, we still have nparams < max_params */
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params[nparams++] = pos;
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pos = strstr(pos, itsep);
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if (pos != NULL)
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{
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*pos = '\0';
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pos++;
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}
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else
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break;
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}
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/* Add the terminator marker; we left room for it in the palloc's */
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params[nparams] = NULL;
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return params;
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}
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#endif /* USE_LIBXSLT */
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