vtkXMLDataParser is broken

Description:

It is actually the same error described here. The Arch VTK package cannot read VTK files:

(  24.361s) [paraview        ]       vtkXMLParser.cxx:375    ERR| vtkXMLDataParser (0x594129186810): Error parsing XML in stream at line 22, column 25, byte index 1327: not well-formed (invalid token)
(  24.374s) [paraview        ]       vtkXMLReader.cxx:520    ERR| vtkXMLUnstructuredGridReader (0x594128f09520): Error parsing input file.  ReadXMLInformation aborting.

Additional info:

• package version(s): 9.3.0-8
• config and/or log files:
• link to upstream bug report, if any: https://discourse.paraview.org/t/i-cannot-read-a-vtp-file-i-could-open-yesterday-can-someone-try-to-open-it/13938

I tried the following expat code, using the expat Arch package, on this file:

#include <expat.h>
#include <stdio.h>
#include <string.h>

#define BUFFER_SIZE 100000

/* track the current level in the xml tree */
static int      depth = 0;

static char    *last_content;

/* first when start element is encountered */
void
start_element(void *data, const char *element, const char **attribute)
{
    int             i;

    for (i = 0; i < depth; i++) {
        printf(" ");
    }

    printf("%s", element);

    for (i = 0; attribute[i]; i += 2) {
        printf(" %s= '%s'", attribute[i], attribute[i + 1]);
    }

    printf("\n");
    depth++;
}

/* decrement the current level of the tree */
void
end_element(void *data, const char *el)
{
    int             i;
    for (i = 0; i < depth; i++) {
        printf(" ");
    }
    printf("Content of element %s was \"%s\"\n", el, last_content);
    depth--;
}

void
handle_data(void *data, const char *content, int length)
{
    char           *tmp = (char*)malloc(length);
    strncpy(tmp, content, length);
    tmp[length] = '\0';
    data = (void *) tmp;
    last_content = tmp;         /* TODO: concatenate the text nodes? */
}

int
parse_xml(char *buff, size_t buff_size)
{
    FILE           *fp;
    fp = fopen("ref.vtu", "r");
    if (fp == NULL) {
        printf("Failed to open file\n");
        return 1;
    }

    XML_Parser      parser = XML_ParserCreate(NULL);
    XML_SetElementHandler(parser, start_element, end_element);
    XML_SetCharacterDataHandler(parser, handle_data);

    memset(buff, 0, buff_size);
    printf("strlen(buff) before parsing: %d\n", strlen(buff));

    size_t          file_size = 0;
    file_size = fread(buff, sizeof(char), buff_size, fp);

    /* parse the xml */
    if (XML_Parse(parser, buff, strlen(buff), XML_TRUE) == XML_STATUS_ERROR) {
        printf("Error: %s\n", XML_ErrorString(XML_GetErrorCode(parser)));
    }

    fclose(fp);
    XML_ParserFree(parser);

    return 0;
}

int
main(int argc, char **argv)
{
    int             result;
    char            buffer[BUFFER_SIZE];
    result = parse_xml(buffer, BUFFER_SIZE);
    printf("Result is %i\n", result);
    return 0;
}

And it seems that the VTK is loaded just fine. However, I also tried to recompile the VTK library with the option -DVTK_MODULE_USE_EXTERNAL_VTK_expat=ON, but I got the same error. So I suppose expat is just ok, and the problem is in VTK itself.

Steps to reproduce:

1. Download the vtp file from the discussion: https://discourse.paraview.org/uploads/short-url/mmC8dLkm86pEai3nsLYNQcRDyLX.vtp
2. Try to load it in VTK