* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.67 2008/01/12 21:14:08 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.68 2008/01/15 18:56:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
*/
/*
- * Note on memory management: Via callbacks, libxml is told to use
- * palloc and friends for memory management. Sometimes, libxml
- * allocates global structures in the hope that it can reuse them
- * later on, but if "later" is much later, the memory context
- * management of PostgreSQL will have blown those structures away
- * without telling libxml about it. Therefore, it is important to
- * call xmlCleanupParser() or perhaps some other cleanup function
- * after using such functions, for example something from
- * libxml/parser.h or libxml/xmlsave.h. Unfortunately, you cannot
- * readily tell from the API documentation when that happens, so
- * careful evaluation is necessary when introducing new libxml APIs
- * here.
+ * Notes on memory management:
+ *
+ * Via callbacks, libxml is told to use palloc and friends for memory
+ * management, within a context that we reset at transaction end (and also at
+ * subtransaction abort) to prevent memory leaks. Resetting at transaction or
+ * subtransaction abort is necessary since we might have thrown a longjmp
+ * while some data structures were not linked from anywhere persistent.
+ * Resetting at transaction commit might not be necessary, but seems a good
+ * idea to forestall long-term leaks.
+ *
+ * Sometimes libxml allocates global structures in the hope that it can reuse
+ * them later on. Therefore, before resetting LibxmlContext, we must tell
+ * libxml to discard any global data it has. The libxml API documentation is
+ * not very good about specifying this, but for now we assume that
+ * xmlCleanupParser() will get rid of anything we need to worry about.
+ *
+ * We use palloc --- which will throw a longjmp on error --- for allocation
+ * callbacks that officially should act like malloc, ie, return NULL on
+ * out-of-memory. This is a bit risky since there is a chance of leaving
+ * persistent libxml data structures in an inconsistent partially-constructed
+ * state, perhaps leading to crash in xmlCleanupParser(). However, as of
+ * early 2008 it is *known* that libxml can crash on out-of-memory due to
+ * inadequate checks for NULL returns, so this behavior seems the lesser
+ * of two evils.
*/
#include "postgres.h"
#ifdef USE_LIBXML
static StringInfo xml_err_buf = NULL;
+static MemoryContext LibxmlContext = NULL;
static void xml_init(void);
+static void xml_memory_init(void);
+static void xml_memory_cleanup(void);
static void *xml_palloc(size_t size);
static void *xml_repalloc(void *ptr, size_t size);
static void xml_pfree(void *ptr);
text *data = PG_GETARG_TEXT_P(0);
text *dtdOrUri = PG_GETARG_TEXT_P(1);
bool result = false;
- xmlParserCtxtPtr ctxt = NULL;
- xmlDocPtr doc = NULL;
- xmlDtdPtr dtd = NULL;
+ xmlParserCtxtPtr ctxt;
+ xmlDocPtr doc;
+ xmlDtdPtr dtd;
xml_init();
-
- /* We use a PG_TRY block to ensure libxml parser is cleaned up on error */
- PG_TRY();
- {
- xmlInitParser();
- ctxt = xmlNewParserCtxt();
- if (ctxt == NULL)
- xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
- "could not allocate parser context");
-
- doc = xmlCtxtReadMemory(ctxt, (char *) VARDATA(data),
- VARSIZE(data) - VARHDRSZ,
- NULL, NULL, 0);
- if (doc == NULL)
- xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
- "could not parse XML data");
+ xmlInitParser();
+ ctxt = xmlNewParserCtxt();
+ if (ctxt == NULL)
+ xml_ereport(ERROR, ERRCODE_OUT_OF_MEMORY,
+ "could not allocate parser context");
+
+ doc = xmlCtxtReadMemory(ctxt, (char *) VARDATA(data),
+ VARSIZE(data) - VARHDRSZ,
+ NULL, NULL, 0);
+ if (doc == NULL)
+ xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
+ "could not parse XML data");
#if 0
- uri = xmlCreateURI();
- elog(NOTICE, "dtd - %s", dtdOrUri);
- dtd = palloc(sizeof(xmlDtdPtr));
- uri = xmlParseURI(dtdOrUri);
- if (uri == NULL)
- xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
- "not implemented yet... (TODO)");
- else
+ uri = xmlCreateURI();
+ elog(NOTICE, "dtd - %s", dtdOrUri);
+ dtd = palloc(sizeof(xmlDtdPtr));
+ uri = xmlParseURI(dtdOrUri);
+ if (uri == NULL)
+ xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
+ "not implemented yet... (TODO)");
+ else
#endif
- dtd = xmlParseDTD(NULL, xml_text2xmlChar(dtdOrUri));
+ dtd = xmlParseDTD(NULL, xml_text2xmlChar(dtdOrUri));
- if (dtd == NULL)
- xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
- "could not load DTD");
+ if (dtd == NULL)
+ xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
+ "could not load DTD");
- if (xmlValidateDtd(xmlNewValidCtxt(), doc, dtd) == 1)
- result = true;
+ if (xmlValidateDtd(xmlNewValidCtxt(), doc, dtd) == 1)
+ result = true;
- if (!result)
- xml_ereport(NOTICE, ERRCODE_INVALID_XML_DOCUMENT,
- "validation against DTD failed");
+ if (!result)
+ xml_ereport(NOTICE, ERRCODE_INVALID_XML_DOCUMENT,
+ "validation against DTD failed");
#if 0
- if (uri)
- xmlFreeURI(uri);
- uri = NULL;
+ xmlFreeURI(uri);
#endif
- if (dtd)
- xmlFreeDtd(dtd);
- dtd = NULL;
- if (doc)
- xmlFreeDoc(doc);
- doc = NULL;
- if (ctxt)
- xmlFreeParserCtxt(ctxt);
- ctxt = NULL;
- xmlCleanupParser();
- }
- PG_CATCH();
- {
-#if 0
- if (uri)
- xmlFreeURI(uri);
-#endif
- if (dtd)
- xmlFreeDtd(dtd);
- if (doc)
- xmlFreeDoc(doc);
- if (ctxt)
- xmlFreeParserCtxt(ctxt);
- xmlCleanupParser();
-
- PG_RE_THROW();
- }
- PG_END_TRY();
+ xmlFreeDtd(dtd);
+ xmlFreeDoc(doc);
+ xmlFreeParserCtxt(ctxt);
PG_RETURN_BOOL(result);
#else /* not USE_LIBXML */
}
+/*
+ * xml cleanup function for transaction end. This is also called on
+ * subtransaction abort; see notes at top of file for rationale.
+ */
+void
+AtEOXact_xml(void)
+{
+#ifdef USE_LIBXML
+ xml_memory_cleanup();
+#endif
+}
+
+
#ifdef USE_LIBXML
/*
xmlSetGenericErrorFunc(NULL, xml_errorHandler);
/* Set up memory allocation our way, too */
- xmlMemSetup(xml_pfree, xml_palloc, xml_repalloc, xml_pstrdup);
+ xml_memory_init();
/* Check library compatibility */
LIBXML_TEST_VERSION;
- /* The above calls xmlInitParser(); must clean up dangling pointers */
- xmlCleanupParser();
-
first_time = false;
}
else
* about, anyway.
*/
xmlSetGenericErrorFunc(NULL, xml_errorHandler);
- xmlMemSetup(xml_pfree, xml_palloc, xml_repalloc, xml_pstrdup);
+ xml_memory_init();
}
}
* Convert a C string to XML internal representation
*
* TODO maybe, libxml2's xmlreader is better? (do not construct DOM,
- * yet do not use SAX - see xml_reader.c)
+ * yet do not use SAX - see xmlreader.c)
*/
static xmlDocPtr
xml_parse(text *data, XmlOptionType xmloption_arg, bool preserve_whitespace,
int32 len;
xmlChar *string;
xmlChar *utf8string;
- xmlParserCtxtPtr ctxt = NULL;
- xmlDocPtr doc = NULL;
+ xmlParserCtxtPtr ctxt;
+ xmlDocPtr doc;
len = VARSIZE(data) - VARHDRSZ; /* will be useful later */
string = xml_text2xmlChar(data);
PG_UTF8);
xml_init();
+ xmlInitParser();
+ ctxt = xmlNewParserCtxt();
+ if (ctxt == NULL)
+ xml_ereport(ERROR, ERRCODE_OUT_OF_MEMORY,
+ "could not allocate parser context");
- /* We use a PG_TRY block to ensure libxml parser is cleaned up on error */
- PG_TRY();
+ if (xmloption_arg == XMLOPTION_DOCUMENT)
{
- xmlInitParser();
- ctxt = xmlNewParserCtxt();
- if (ctxt == NULL)
- xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
- "could not allocate parser context");
-
- if (xmloption_arg == XMLOPTION_DOCUMENT)
- {
- /*
- * Note, that here we try to apply DTD defaults
- * (XML_PARSE_DTDATTR) according to SQL/XML:10.16.7.d: 'Default
- * valies defined by internal DTD are applied'. As for external
- * DTDs, we try to support them too, (see SQL/XML:10.16.7.e)
- */
- doc = xmlCtxtReadDoc(ctxt, utf8string,
- NULL,
- "UTF-8",
- XML_PARSE_NOENT | XML_PARSE_DTDATTR
- | (preserve_whitespace ? 0 : XML_PARSE_NOBLANKS));
- if (doc == NULL)
- xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
- "invalid XML document");
- }
- else
- {
- int res_code;
- size_t count;
- xmlChar *version = NULL;
- int standalone = -1;
-
- doc = xmlNewDoc(NULL);
-
- res_code = parse_xml_decl(utf8string, &count, &version, NULL, &standalone);
- if (res_code != 0)
- xml_ereport_by_code(ERROR, ERRCODE_INVALID_XML_CONTENT,
- "invalid XML content: invalid XML declaration", res_code);
-
- res_code = xmlParseBalancedChunkMemory(doc, NULL, NULL, 0, utf8string + count, NULL);
- if (res_code != 0)
- xml_ereport(ERROR, ERRCODE_INVALID_XML_CONTENT,
- "invalid XML content");
-
- doc->version = xmlStrdup(version);
- doc->encoding = xmlStrdup((xmlChar *) "UTF-8");
- doc->standalone = standalone;
- }
-
- if (ctxt)
- xmlFreeParserCtxt(ctxt);
- ctxt = NULL;
- xmlCleanupParser();
+ /*
+ * Note, that here we try to apply DTD defaults
+ * (XML_PARSE_DTDATTR) according to SQL/XML:10.16.7.d: 'Default
+ * values defined by internal DTD are applied'. As for external
+ * DTDs, we try to support them too, (see SQL/XML:10.16.7.e)
+ */
+ doc = xmlCtxtReadDoc(ctxt, utf8string,
+ NULL,
+ "UTF-8",
+ XML_PARSE_NOENT | XML_PARSE_DTDATTR
+ | (preserve_whitespace ? 0 : XML_PARSE_NOBLANKS));
+ if (doc == NULL)
+ xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
+ "invalid XML document");
}
- PG_CATCH();
+ else
{
- if (doc)
- xmlFreeDoc(doc);
- if (ctxt)
- xmlFreeParserCtxt(ctxt);
- xmlCleanupParser();
+ int res_code;
+ size_t count;
+ xmlChar *version = NULL;
+ int standalone = -1;
- PG_RE_THROW();
+ doc = xmlNewDoc(NULL);
+
+ res_code = parse_xml_decl(utf8string,
+ &count, &version, NULL, &standalone);
+ if (res_code != 0)
+ xml_ereport_by_code(ERROR, ERRCODE_INVALID_XML_CONTENT,
+ "invalid XML content: invalid XML declaration",
+ res_code);
+
+ res_code = xmlParseBalancedChunkMemory(doc, NULL, NULL, 0,
+ utf8string + count, NULL);
+ if (res_code != 0)
+ xml_ereport(ERROR, ERRCODE_INVALID_XML_CONTENT,
+ "invalid XML content");
+
+ doc->version = xmlStrdup(version);
+ doc->encoding = xmlStrdup((xmlChar *) "UTF-8");
+ doc->standalone = standalone;
}
- PG_END_TRY();
+
+ xmlFreeParserCtxt(ctxt);
return doc;
}
}
+/*
+ * Manage the special context used for all libxml allocations
+ */
+static void
+xml_memory_init(void)
+{
+ /*
+ * Create memory context if not there already. We make it a child of
+ * TopMemoryContext, even though our current policy is that it doesn't
+ * survive past transaction end, because we want to be really really
+ * sure it doesn't go away before we've called xmlCleanupParser().
+ */
+ if (LibxmlContext == NULL)
+ LibxmlContext = AllocSetContextCreate(TopMemoryContext,
+ "LibxmlContext",
+ ALLOCSET_DEFAULT_MINSIZE,
+ ALLOCSET_DEFAULT_INITSIZE,
+ ALLOCSET_DEFAULT_MAXSIZE);
+
+ /* Re-establish the callbacks even if already set */
+ xmlMemSetup(xml_pfree, xml_palloc, xml_repalloc, xml_pstrdup);
+}
+
+static void
+xml_memory_cleanup(void)
+{
+ if (LibxmlContext != NULL)
+ {
+ /* Give libxml a chance to clean up dangling pointers */
+ xmlCleanupParser();
+
+ /* And flush the context */
+ MemoryContextDelete(LibxmlContext);
+ LibxmlContext = NULL;
+ }
+}
+
/*
* Wrappers for memory management functions
*/
static void *
xml_palloc(size_t size)
{
- return palloc(size);
+ return MemoryContextAlloc(LibxmlContext, size);
}
static char *
xml_pstrdup(const char *string)
{
- return pstrdup(string);
+ return MemoryContextStrdup(LibxmlContext, string);
}
xmltype *data = PG_GETARG_XML_P(1);
ArrayType *namespaces = PG_GETARG_ARRAYTYPE_P(2);
ArrayBuildState *astate = NULL;
- xmlParserCtxtPtr ctxt = NULL;
- xmlDocPtr doc = NULL;
- xmlXPathContextPtr xpathctx = NULL;
- xmlXPathCompExprPtr xpathcomp = NULL;
- xmlXPathObjectPtr xpathobj = NULL;
+ xmlParserCtxtPtr ctxt;
+ xmlDocPtr doc;
+ xmlXPathContextPtr xpathctx;
+ xmlXPathCompExprPtr xpathcomp;
+ xmlXPathObjectPtr xpathobj;
char *datastr;
int32 len;
int32 xpath_len;
xpath_expr[xpath_len + 2] = '\0';
xpath_len += 2;
- /* We use a PG_TRY block to ensure libxml parser is cleaned up on error */
- PG_TRY();
- {
- xmlInitParser();
+ xmlInitParser();
- /*
- * redundant XML parsing (two parsings for the same value during one
- * command execution are possible)
- */
- ctxt = xmlNewParserCtxt();
- if (ctxt == NULL)
- xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
- "could not allocate parser context");
- doc = xmlCtxtReadMemory(ctxt, (char *) string, len, NULL, NULL, 0);
- if (doc == NULL)
- xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
- "could not parse XML data");
- xpathctx = xmlXPathNewContext(doc);
- if (xpathctx == NULL)
- xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
- "could not allocate XPath context");
- xpathctx->node = xmlDocGetRootElement(doc);
- if (xpathctx->node == NULL)
- xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
- "could not find root XML element");
-
- /* register namespaces, if any */
- if (ns_count > 0)
+ /*
+ * redundant XML parsing (two parsings for the same value during one
+ * command execution are possible)
+ */
+ ctxt = xmlNewParserCtxt();
+ if (ctxt == NULL)
+ xml_ereport(ERROR, ERRCODE_OUT_OF_MEMORY,
+ "could not allocate parser context");
+ doc = xmlCtxtReadMemory(ctxt, (char *) string, len, NULL, NULL, 0);
+ if (doc == NULL)
+ xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
+ "could not parse XML data");
+ xpathctx = xmlXPathNewContext(doc);
+ if (xpathctx == NULL)
+ xml_ereport(ERROR, ERRCODE_OUT_OF_MEMORY,
+ "could not allocate XPath context");
+ xpathctx->node = xmlDocGetRootElement(doc);
+ if (xpathctx->node == NULL)
+ xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
+ "could not find root XML element");
+
+ /* register namespaces, if any */
+ if (ns_count > 0)
+ {
+ for (i = 0; i < ns_count; i++)
{
- for (i = 0; i < ns_count; i++)
- {
- char *ns_name;
- char *ns_uri;
-
- if (ns_names_uris_nulls[i * 2] ||
- ns_names_uris_nulls[i * 2 + 1])
- ereport(ERROR,
- (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
- errmsg("neither namespace name nor URI may be null")));
- ns_name = _textout(ns_names_uris[i * 2]);
- ns_uri = _textout(ns_names_uris[i * 2 + 1]);
- if (xmlXPathRegisterNs(xpathctx,
- (xmlChar *) ns_name,
- (xmlChar *) ns_uri) != 0)
- ereport(ERROR, /* is this an internal error??? */
- (errmsg("could not register XML namespace with name \"%s\" and URI \"%s\"",
- ns_name, ns_uri)));
- }
+ char *ns_name;
+ char *ns_uri;
+
+ if (ns_names_uris_nulls[i * 2] ||
+ ns_names_uris_nulls[i * 2 + 1])
+ ereport(ERROR,
+ (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+ errmsg("neither namespace name nor URI may be null")));
+ ns_name = _textout(ns_names_uris[i * 2]);
+ ns_uri = _textout(ns_names_uris[i * 2 + 1]);
+ if (xmlXPathRegisterNs(xpathctx,
+ (xmlChar *) ns_name,
+ (xmlChar *) ns_uri) != 0)
+ ereport(ERROR, /* is this an internal error??? */
+ (errmsg("could not register XML namespace with name \"%s\" and URI \"%s\"",
+ ns_name, ns_uri)));
}
+ }
- xpathcomp = xmlXPathCompile(xpath_expr);
- if (xpathcomp == NULL) /* TODO: show proper XPath error details */
- xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
- "invalid XPath expression");
-
- xpathobj = xmlXPathCompiledEval(xpathcomp, xpathctx);
- if (xpathobj == NULL) /* TODO: reason? */
- ereport(ERROR,
- (errmsg("could not create XPath object")));
-
- xmlXPathFreeCompExpr(xpathcomp);
- xpathcomp = NULL;
+ xpathcomp = xmlXPathCompile(xpath_expr);
+ if (xpathcomp == NULL) /* TODO: show proper XPath error details */
+ xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
+ "invalid XPath expression");
- /* return empty array in cases when nothing is found */
- if (xpathobj->nodesetval == NULL)
- res_nitems = 0;
- else
- res_nitems = xpathobj->nodesetval->nodeNr;
+ xpathobj = xmlXPathCompiledEval(xpathcomp, xpathctx);
+ if (xpathobj == NULL) /* TODO: reason? */
+ ereport(ERROR,
+ (errmsg("could not create XPath object")));
- if (res_nitems)
- for (i = 0; i < xpathobj->nodesetval->nodeNr; i++)
- {
- Datum elem;
- bool elemisnull = false;
+ xmlXPathFreeCompExpr(xpathcomp);
- elem = PointerGetDatum(xml_xmlnodetoxmltype(xpathobj->nodesetval->nodeTab[i]));
- astate = accumArrayResult(astate, elem,
- elemisnull, XMLOID,
- CurrentMemoryContext);
- }
+ /* return empty array in cases when nothing is found */
+ if (xpathobj->nodesetval == NULL)
+ res_nitems = 0;
+ else
+ res_nitems = xpathobj->nodesetval->nodeNr;
- xmlXPathFreeObject(xpathobj);
- xpathobj = NULL;
- xmlXPathFreeContext(xpathctx);
- xpathctx = NULL;
- xmlFreeDoc(doc);
- doc = NULL;
- xmlFreeParserCtxt(ctxt);
- ctxt = NULL;
- xmlCleanupParser();
- }
- PG_CATCH();
+ if (res_nitems)
{
- if (xpathcomp)
- xmlXPathFreeCompExpr(xpathcomp);
- if (xpathobj)
- xmlXPathFreeObject(xpathobj);
- if (xpathctx)
- xmlXPathFreeContext(xpathctx);
- if (doc)
- xmlFreeDoc(doc);
- if (ctxt)
- xmlFreeParserCtxt(ctxt);
- xmlCleanupParser();
+ for (i = 0; i < xpathobj->nodesetval->nodeNr; i++)
+ {
+ Datum elem;
+ bool elemisnull = false;
- PG_RE_THROW();
+ elem = PointerGetDatum(xml_xmlnodetoxmltype(xpathobj->nodesetval->nodeTab[i]));
+ astate = accumArrayResult(astate, elem,
+ elemisnull, XMLOID,
+ CurrentMemoryContext);
+ }
}
- PG_END_TRY();
+
+ xmlXPathFreeObject(xpathobj);
+ xmlXPathFreeContext(xpathctx);
+ xmlFreeDoc(doc);
+ xmlFreeParserCtxt(ctxt);
if (res_nitems == 0)
PG_RETURN_ARRAYTYPE_P(construct_empty_array(XMLOID));
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