Fix libxml and soap extension with libxml >= 2.12.0 (#9572)

Summary:
libxml 2.12.0 changes the API to return `const xmlError*` in several places.[1] As a fix, use auto variables for storing the output of xmlGetLastError() and make the signature of our error handler function dependent on the libxml version.

Split from #9564.

[1] https://gitlab.gnome.org/GNOME/libxml2/-/blob/86401cc3d293d6ea3c4552885e3cadcd952021d1/NEWS#L392

Pull Request resolved: #9572

Reviewed By: Wilfred

Differential Revision: D67922353

fbshipit-source-id: 36eded2295fdd60d15ff559d4d79eb5732c5598f

hphp/runtime/ext/libxml/ext_libxml.cpp

@@ -36,6 +36,7 @@
 #include <libxml/uri.h>
 #include <libxml/xmlerror.h>
 #include <libxml/xmlsave.h>
+#include <libxml/xmlversion.h>
 #ifdef LIBXML_SCHEMAS_ENABLED
 #include <libxml/relaxng.h>
 #include <libxml/xmlschemas.h>
@@ -624,7 +625,11 @@ String libxml_get_valid_file_path(const String& source) {
   return file_dest;
 }
 
+#if LIBXML_VERSION >= 21200
+static void libxml_error_handler(void* /*userData*/, const xmlError* error) {
+#else
 static void libxml_error_handler(void* /*userData*/, xmlErrorPtr error) {
+#endif
   if (rl_libxml_request_data->m_suppress_error) {
     return;
   }
@@ -642,7 +647,7 @@ static void libxml_error_handler(void* /*userData*/, xmlErrorPtr error) {
   }
 }
 
-static Object create_libxmlerror(xmlError &error) {
+static Object create_libxmlerror(const xmlError &error) {
   Object ret{ LibXMLError::classof() };
   // Setting only public properties
   ret->setProp(nullctx, s_level.get(), make_tv<KindOfInt64>(error.level));
@@ -678,7 +683,7 @@ Array HHVM_FUNCTION(libxml_get_errors) {
 }
 
 Variant HHVM_FUNCTION(libxml_get_last_error) {
-  xmlErrorPtr error = xmlGetLastError();
+  auto error = xmlGetLastError();
   if (error) {
     return create_libxmlerror(*error);
   }

hphp/runtime/ext/soap/sdl.cpp

@@ -178,7 +178,7 @@ static void load_wsdl_ex(char *struri, sdlCtx *ctx, bool include,
     wsdl = soap_xmlParseFile(struri);
   }
   if (!wsdl) {
-    xmlErrorPtr xmlErrorPtr = xmlGetLastError();
+    auto xmlErrorPtr = xmlGetLastError();
     if (xmlErrorPtr) {
       throw SoapException("Parsing WSDL: Couldn't load from '%s' : %s",
                           struri, xmlErrorPtr->message);