MDEV-33439 Fix build with libxml2 2.12

libxml2 2.12.0 made `xmlGetLastError()` return `const` pointer: https://gitlab.gnome.org/GNOME/libxml2/-/commit/61034116d0a3c8b295c6137956adc3ae55720711 Clang 16 does not like this: error: assigning to 'xmlErrorPtr' (aka '_xmlError *') from 'const xmlError *' (aka 'const _xmlError *') discards qualifiers error: cannot initialize a variable of type 'xmlErrorPtr' (aka '_xmlError *') with an rvalue of type 'const xmlError *' (aka 'const _xmlError *') Let’s update the variables to `const`. For older versions, it will be automatically converted. But then `xmlResetError(xmlError*)` will not like the `const` pointer: error: no matching function for call to 'xmlResetError' note: candidate function not viable: 1st argument ('const xmlError *' (aka 'const _xmlError *')) would lose const qualifier Let’s replace it with `xmlResetLastError()`. ALso remove `LIBXMLDOC::Xerr` protected member property. It was introduced in 65b0e54 along with the `xmlResetError` calls. It does not appear to be used for anything.

Author: jtojnar

storage/connect/libdoc.cpp

@@ -93,7 +93,6 @@ class LIBXMLDOC : public XMLDOCUMENT {
  xmlXPathContextPtr Ctxp;
  xmlXPathObjectPtr Xop;
  xmlXPathObjectPtr NlXop;
- xmlErrorPtr Xerr;
  char *Buf; // Temporary
  bool Nofreelist;
 }; // end of class LIBXMLDOC
@@ -327,7 +326,6 @@ LIBXMLDOC::LIBXMLDOC(char *nsl, char *nsdf, char *enc, PFBLOCK fp)
  Ctxp = NULL;
  Xop = NULL;
  NlXop = NULL;
- Xerr = NULL;
  Buf = NULL;
  Nofreelist = false;
  } // end of LIBXMLDOC constructor
@@ -365,8 +363,8 @@ bool LIBXMLDOC::ParseFile(PGLOBAL g, char *fn)
  Encoding = (char*)Docp->encoding;
 
  return false;
- } else if ((Xerr = xmlGetLastError()))
- xmlResetError(Xerr);
+ } else if (xmlGetLastError())
+ xmlResetLastError();
 
  return true;
  } // end of ParseFile
@@ -505,9 +503,9 @@ int LIBXMLDOC::DumpDoc(PGLOBAL g, char *ofn)
 #if 1
  // This function does not crash (
  if (xmlSaveFormatFileEnc((const char *)ofn, Docp, Encoding, 0) < 0) {
- xmlErrorPtr err = xmlGetLastError();
+ const xmlError *err = xmlGetLastError();
  strcpy(g->Message, (err) ? err->message : "Error saving XML doc");
- xmlResetError(Xerr);
+ xmlResetLastError();
  rc = -1;
  } // endif Save
 // rc = xmlDocDump(of, Docp);
@@ -546,35 +544,35 @@ void LIBXMLDOC::CloseDoc(PGLOBAL g, PFBLOCK xp)
  if (Nlist) {
  xmlXPathFreeNodeSet(Nlist);
 
- if ((Xerr = xmlGetLastError()))
- xmlResetError(Xerr);
+ if (xmlGetLastError())
+ xmlResetLastError();
 
  Nlist = NULL;
  } // endif Nlist
 
  if (Xop) {
  xmlXPathFreeObject(Xop);
 
- if ((Xerr = xmlGetLastError()))
- xmlResetError(Xerr);
+ if (xmlGetLastError())
+ xmlResetLastError();
 
  Xop = NULL;
  } // endif Xop
 
  if (NlXop) {
  xmlXPathFreeObject(NlXop);
 
- if ((Xerr = xmlGetLastError()))
- xmlResetError(Xerr);
+ if (xmlGetLastError())
+ xmlResetLastError();
 
  NlXop = NULL;
  } // endif NlXop
 
  if (Ctxp) {
  xmlXPathFreeContext(Ctxp);
 
- if ((Xerr = xmlGetLastError()))
- xmlResetError(Xerr);
+ if (xmlGetLastError())
+ xmlResetLastError();
 
  Ctxp = NULL;
  } // endif Ctxp
@@ -590,6 +588,7 @@ void LIBXMLDOC::CloseDoc(PGLOBAL g, PFBLOCK xp)
 /******************************************************************/
 xmlNodeSetPtr LIBXMLDOC::GetNodeList(PGLOBAL g, xmlNodePtr np, char *xp)
  {
+ const xmlError *xerr;
  xmlNodeSetPtr nl;
 
  if (trace(1))
@@ -649,11 +648,11 @@ xmlNodeSetPtr LIBXMLDOC::GetNodeList(PGLOBAL g, xmlNodePtr np, char *xp)
  } else
  xmlXPathFreeObject(Xop); // Caused node not found
 
- if ((Xerr = xmlGetLastError())) {
- strcpy(g->Message, Xerr->message);
- xmlResetError(Xerr);
+ if ((xerr = xmlGetLastError())) {
+ strcpy(g->Message, xerr->message);
+ xmlResetLastError();
  return NULL;
- } // endif Xerr
+ } // endif xerr
 
  } // endif Xop
 
@@ -1079,7 +1078,7 @@ void XML2NODE::AddText(PGLOBAL g, PCSZ txtp)
 /******************************************************************/
 void XML2NODE::DeleteChild(PGLOBAL g, PXNODE dnp)
  {
- xmlErrorPtr xerr;
+ const xmlError *xerr;
 
  if (trace(1))
  htrc("DeleteChild: node=%p\n", dnp);
@@ -1122,7 +1121,7 @@ void XML2NODE::DeleteChild(PGLOBAL g, PXNODE dnp)
  if (trace(1))
  htrc("DeleteChild: errmsg=%-.256s\n", xerr->message);
 
- xmlResetError(xerr);
+ xmlResetLastError();
  } // end of DeleteChild
 
 /* -------------------- class XML2NODELIST ---------------------- */