aboutsummaryrefslogtreecommitdiff
path: root/gdb/xml-support.c
blob: d4cd89c03398208a3ca97538b0744586dc0ff6e0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
/* Helper routines for parsing XML using Expat.

   Copyright (C) 2006-2019 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "gdbcmd.h"
#include "xml-support.h"
#include "common/filestuff.h"
#include "safe-ctype.h"
#include <vector>
#include <string>

/* Debugging flag.  */
static int debug_xml;

/* The contents of this file are only useful if XML support is
   available.  */
#ifdef HAVE_LIBEXPAT

#include "gdb_expat.h"

/* The maximum depth of <xi:include> nesting.  No need to be miserly,
   we just want to avoid running out of stack on loops.  */
#define MAX_XINCLUDE_DEPTH 30

/* Simplified XML parser infrastructure.  */

/* A parsing level -- used to keep track of the current element
   nesting.  */
struct scope_level
{
  explicit scope_level (const gdb_xml_element *elements_ = NULL)
    : elements (elements_),
      element (NULL),
      seen (0)
  {}

  /* Elements we allow at this level.  */
  const struct gdb_xml_element *elements;

  /* The element which we are within.  */
  const struct gdb_xml_element *element;

  /* Mask of which elements we've seen at this level (used for
     optional and repeatable checking).  */
  unsigned int seen;

  /* Body text accumulation.  */
  std::string body;
};

/* The parser itself, and our additional state.  */
struct gdb_xml_parser
{
  gdb_xml_parser (const char *name,
		  const gdb_xml_element *elements,
		  void *user_data);
  ~gdb_xml_parser();

  /* Associate DTD_NAME, which must be the name of a compiled-in DTD,
     with the parser.  */
  void use_dtd (const char *dtd_name);

  /* Return the name of the expected / default DTD, if specified.  */
  const char *dtd_name ()
  { return m_dtd_name; }

  /* Invoke the parser on BUFFER.  BUFFER is the data to parse, which
     should be NUL-terminated.

     The return value is 0 for success or -1 for error.  It may throw,
     but only if something unexpected goes wrong during parsing; parse
     errors will be caught, warned about, and reported as failure.  */
  int parse (const char *buffer);

  /* Issue a debugging message.  */
  void vdebug (const char *format, va_list ap)
    ATTRIBUTE_PRINTF (2, 0);

  /* Issue an error message, and stop parsing.  */
  void verror (const char *format, va_list ap)
    ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 0);

  void body_text (const XML_Char *text, int length);
  void start_element (const XML_Char *name, const XML_Char **attrs);
  void end_element (const XML_Char *name);

  /* Return the name of this parser.  */
  const char *name ()
  { return m_name; }

  /* Return the user's callback data, for handlers.  */
  void *user_data ()
  { return m_user_data; };

  /* Are we the special <xi:include> parser?  */
  void set_is_xinclude (bool is_xinclude)
  { m_is_xinclude = is_xinclude; }

  /* A thrown error, if any.  */
  void set_error (gdb_exception error)
  {
    m_error = error;
#ifdef HAVE_XML_STOPPARSER
    XML_StopParser (m_expat_parser, XML_FALSE);
#endif
  }

  /* Return the underlying expat parser.  */
  XML_Parser expat_parser ()
  { return m_expat_parser; }

private:
  /* The underlying expat parser.  */
  XML_Parser m_expat_parser;

  /* Name of this parser.  */
  const char *m_name;

  /* The user's callback data, for handlers.  */
  void *m_user_data;

  /* Scoping stack.  */
  std::vector<scope_level> m_scopes;

/* A thrown error, if any.  */
  struct gdb_exception m_error;

  /* The line of the thrown error, or 0.  */
  int m_last_line;

  /* The name of the expected / default DTD, if specified.  */
  const char *m_dtd_name;

  /* Are we the special <xi:include> parser?  */
  bool m_is_xinclude;
};

/* Process some body text.  We accumulate the text for later use; it's
   wrong to do anything with it immediately, because a single block of
   text might be broken up into multiple calls to this function.  */

void
gdb_xml_parser::body_text (const XML_Char *text, int length)
{
  if (m_error.reason < 0)
    return;

  scope_level &scope = m_scopes.back ();
  scope.body.append (text, length);
}

static void
gdb_xml_body_text (void *data, const XML_Char *text, int length)
{
  struct gdb_xml_parser *parser = (struct gdb_xml_parser *) data;

  parser->body_text (text, length);
}

/* Issue a debugging message from one of PARSER's handlers.  */

void
gdb_xml_parser::vdebug (const char *format, va_list ap)
{
  int line = XML_GetCurrentLineNumber (m_expat_parser);

  std::string message = string_vprintf (format, ap);
  if (line)
    fprintf_unfiltered (gdb_stderr, "%s (line %d): %s\n",
			m_name, line, message.c_str ());
  else
    fprintf_unfiltered (gdb_stderr, "%s: %s\n",
			m_name, message.c_str ());
}

void
gdb_xml_debug (struct gdb_xml_parser *parser, const char *format, ...)
{
  if (!debug_xml)
    return;

  va_list ap;
  va_start (ap, format);
  parser->vdebug (format, ap);
  va_end (ap);
}

/* Issue an error message from one of PARSER's handlers, and stop
   parsing.  */

void
gdb_xml_parser::verror (const char *format, va_list ap)
{
  int line = XML_GetCurrentLineNumber (m_expat_parser);

  m_last_line = line;
  throw_verror (XML_PARSE_ERROR, format, ap);
}

void
gdb_xml_error (struct gdb_xml_parser *parser, const char *format, ...)
{
  va_list ap;
  va_start (ap, format);
  parser->verror (format, ap);
  va_end (ap);
}

/* Find the attribute named NAME in the set of parsed attributes
   ATTRIBUTES.  Returns NULL if not found.  */

struct gdb_xml_value *
xml_find_attribute (std::vector<gdb_xml_value> &attributes,
		    const char *name)
{
  for (gdb_xml_value &value : attributes)
    if (strcmp (value.name, name) == 0)
      return &value;

  return NULL;
}

/* Handle the start of an element.  NAME is the element, and ATTRS are
   the names and values of this element's attributes.  */

void
gdb_xml_parser::start_element (const XML_Char *name,
			       const XML_Char **attrs)
{
  if (m_error.reason < 0)
    return;

  const struct gdb_xml_element *element;
  const struct gdb_xml_attribute *attribute;
  unsigned int seen;

  /* Push an error scope.  If we return or throw an exception before
     filling this in, it will tell us to ignore children of this
     element.  Note we don't take a reference to the element yet
     because further below we'll process the element which may recurse
     back here and push more elements to the vector.  When the
     recursion unrolls all such elements will have been popped back
     already, but if one of those pushes reallocates the vector,
     previous element references will be invalidated.  */
  m_scopes.emplace_back ();

  /* Get a reference to the current scope.  */
  scope_level &scope = m_scopes[m_scopes.size () - 2];

  gdb_xml_debug (this, _("Entering element <%s>"), name);

  /* Find this element in the list of the current scope's allowed
     children.  Record that we've seen it.  */

  seen = 1;
  for (element = scope.elements; element && element->name;
       element++, seen <<= 1)
    if (strcmp (element->name, name) == 0)
      break;

  if (element == NULL || element->name == NULL)
    {
      /* If we're working on XInclude, <xi:include> can be the child
	 of absolutely anything.  Copy the previous scope's element
	 list into the new scope even if there was no match.  */
      if (m_is_xinclude)
	{
	  XML_DefaultCurrent (m_expat_parser);

	  scope_level &unknown_scope = m_scopes.back ();
	  unknown_scope.elements = scope.elements;
	  return;
	}

      gdb_xml_debug (this, _("Element <%s> unknown"), name);
      return;
    }

  if (!(element->flags & GDB_XML_EF_REPEATABLE) && (seen & scope.seen))
    gdb_xml_error (this, _("Element <%s> only expected once"), name);

  scope.seen |= seen;

  std::vector<gdb_xml_value> attributes;

  for (attribute = element->attributes;
       attribute != NULL && attribute->name != NULL;
       attribute++)
    {
      const char *val = NULL;
      const XML_Char **p;
      void *parsed_value;

      for (p = attrs; *p != NULL; p += 2)
	if (!strcmp (attribute->name, p[0]))
	  {
	    val = p[1];
	    break;
	  }

      if (*p != NULL && val == NULL)
	{
	  gdb_xml_debug (this, _("Attribute \"%s\" missing a value"),
			 attribute->name);
	  continue;
	}

      if (*p == NULL && !(attribute->flags & GDB_XML_AF_OPTIONAL))
	{
	  gdb_xml_error (this, _("Required attribute \"%s\" of "
				   "<%s> not specified"),
			 attribute->name, element->name);
	  continue;
	}

      if (*p == NULL)
	continue;

      gdb_xml_debug (this, _("Parsing attribute %s=\"%s\""),
		     attribute->name, val);

      if (attribute->handler)
	parsed_value = attribute->handler (this, attribute, val);
      else
	parsed_value = xstrdup (val);

      attributes.emplace_back (attribute->name, parsed_value);
    }

  /* Check for unrecognized attributes.  */
  if (debug_xml)
    {
      const XML_Char **p;

      for (p = attrs; *p != NULL; p += 2)
	{
	  for (attribute = element->attributes;
	       attribute != NULL && attribute->name != NULL;
	       attribute++)
	    if (strcmp (attribute->name, *p) == 0)
	      break;

	  if (attribute == NULL || attribute->name == NULL)
	    gdb_xml_debug (this, _("Ignoring unknown attribute %s"), *p);
	}
    }

  /* Call the element handler if there is one.  */
  if (element->start_handler)
    element->start_handler (this, element, m_user_data, attributes);

  /* Fill in a new scope level.  Note that we must delay getting a
     back reference till here because above we might have recursed,
     which may have reallocated the vector which invalidates
     iterators/pointers/references.  */
  scope_level &new_scope = m_scopes.back ();
  new_scope.element = element;
  new_scope.elements = element->children;
}

/* Wrapper for gdb_xml_start_element, to prevent throwing exceptions
   through expat.  */

static void
gdb_xml_start_element_wrapper (void *data, const XML_Char *name,
			       const XML_Char **attrs)
{
  struct gdb_xml_parser *parser = (struct gdb_xml_parser *) data;

  try
    {
      parser->start_element (name, attrs);
    }
  catch (const gdb_exception &ex)
    {
      parser->set_error (ex);
    }
}

/* Handle the end of an element.  NAME is the current element.  */

void
gdb_xml_parser::end_element (const XML_Char *name)
{
  if (m_error.reason < 0)
    return;

  struct scope_level *scope = &m_scopes.back ();
  const struct gdb_xml_element *element;
  unsigned int seen;

  gdb_xml_debug (this, _("Leaving element <%s>"), name);

  for (element = scope->elements, seen = 1;
       element != NULL && element->name != NULL;
       element++, seen <<= 1)
    if ((scope->seen & seen) == 0
	&& (element->flags & GDB_XML_EF_OPTIONAL) == 0)
      gdb_xml_error (this, _("Required element <%s> is missing"),
		     element->name);

  /* Call the element processor.  */
  if (scope->element != NULL && scope->element->end_handler)
    {
      const char *body;

      if (scope->body.empty ())
	body = "";
      else
	{
	  int length;

	  length = scope->body.size ();
	  body = scope->body.c_str ();

	  /* Strip leading and trailing whitespace.  */
	  while (length > 0 && ISSPACE (body[length - 1]))
	    length--;
	  scope->body.erase (length);
	  while (*body && ISSPACE (*body))
	    body++;
	}

      scope->element->end_handler (this, scope->element,
				   m_user_data, body);
    }
  else if (scope->element == NULL)
    XML_DefaultCurrent (m_expat_parser);

  /* Pop the scope level.  */
  m_scopes.pop_back ();
}

/* Wrapper for gdb_xml_end_element, to prevent throwing exceptions
   through expat.  */

static void
gdb_xml_end_element_wrapper (void *data, const XML_Char *name)
{
  struct gdb_xml_parser *parser = (struct gdb_xml_parser *) data;

  try
    {
      parser->end_element (name);
    }
  catch (const gdb_exception &ex)
    {
      parser->set_error (ex);
    }
}

/* Free a parser and all its associated state.  */

gdb_xml_parser::~gdb_xml_parser ()
{
  XML_ParserFree (m_expat_parser);
}

/* Initialize a parser.  */

gdb_xml_parser::gdb_xml_parser (const char *name,
				const gdb_xml_element *elements,
				void *user_data)
  : m_name (name),
    m_user_data (user_data),
    m_last_line (0),
    m_dtd_name (NULL),
    m_is_xinclude (false)
{
  m_expat_parser = XML_ParserCreateNS (NULL, '!');
  if (m_expat_parser == NULL)
    malloc_failure (0);

  XML_SetUserData (m_expat_parser, this);

  /* Set the callbacks.  */
  XML_SetElementHandler (m_expat_parser, gdb_xml_start_element_wrapper,
			 gdb_xml_end_element_wrapper);
  XML_SetCharacterDataHandler (m_expat_parser, gdb_xml_body_text);

  /* Initialize the outer scope.  */
  m_scopes.emplace_back (elements);
}

/* External entity handler.  The only external entities we support
   are those compiled into GDB (we do not fetch entities from the
   target).  */

static int XMLCALL
gdb_xml_fetch_external_entity (XML_Parser expat_parser,
			       const XML_Char *context,
			       const XML_Char *base,
			       const XML_Char *systemId,
			       const XML_Char *publicId)
{
  XML_Parser entity_parser;
  const char *text;
  enum XML_Status status;

  if (systemId == NULL)
    {
      gdb_xml_parser *parser
	= (gdb_xml_parser *) XML_GetUserData (expat_parser);

      text = fetch_xml_builtin (parser->dtd_name ());
      if (text == NULL)
	internal_error (__FILE__, __LINE__,
			_("could not locate built-in DTD %s"),
			parser->dtd_name ());
    }
  else
    {
      text = fetch_xml_builtin (systemId);
      if (text == NULL)
	return XML_STATUS_ERROR;
    }

  entity_parser = XML_ExternalEntityParserCreate (expat_parser,
						  context, NULL);

  /* Don't use our handlers for the contents of the DTD.  Just let expat
     process it.  */
  XML_SetElementHandler (entity_parser, NULL, NULL);
  XML_SetDoctypeDeclHandler (entity_parser, NULL, NULL);
  XML_SetXmlDeclHandler (entity_parser, NULL);
  XML_SetDefaultHandler (entity_parser, NULL);
  XML_SetUserData (entity_parser, NULL);

  status = XML_Parse (entity_parser, text, strlen (text), 1);

  XML_ParserFree (entity_parser);
  return status;
}

void
gdb_xml_parser::use_dtd (const char *dtd_name)
{
  enum XML_Error err;

  m_dtd_name = dtd_name;

  XML_SetParamEntityParsing (m_expat_parser,
			     XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE);
  XML_SetExternalEntityRefHandler (m_expat_parser,
				   gdb_xml_fetch_external_entity);

  /* Even if no DTD is provided, use the built-in DTD anyway.  */
  err = XML_UseForeignDTD (m_expat_parser, XML_TRUE);
  if (err != XML_ERROR_NONE)
    internal_error (__FILE__, __LINE__,
		    _("XML_UseForeignDTD failed: %s"),
		    XML_ErrorString (err));
}

/* Invoke PARSER on BUFFER.  BUFFER is the data to parse, which
   should be NUL-terminated.

   The return value is 0 for success or -1 for error.  It may throw,
   but only if something unexpected goes wrong during parsing; parse
   errors will be caught, warned about, and reported as failure.  */

int
gdb_xml_parser::parse (const char *buffer)
{
  enum XML_Status status;
  const char *error_string;

  gdb_xml_debug (this, _("Starting:\n%s"), buffer);

  status = XML_Parse (m_expat_parser, buffer, strlen (buffer), 1);

  if (status == XML_STATUS_OK && m_error.reason == 0)
    return 0;

  if (m_error.reason == RETURN_ERROR
      && m_error.error == XML_PARSE_ERROR)
    {
      gdb_assert (m_error.message != NULL);
      error_string = m_error.what ();
    }
  else if (status == XML_STATUS_ERROR)
    {
      enum XML_Error err = XML_GetErrorCode (m_expat_parser);

      error_string = XML_ErrorString (err);
    }
  else
    {
      gdb_assert (m_error.reason < 0);
      throw_exception (m_error);
    }

  if (m_last_line != 0)
    warning (_("while parsing %s (at line %d): %s"), m_name,
	     m_last_line, error_string);
  else
    warning (_("while parsing %s: %s"), m_name, error_string);

  return -1;
}

int
gdb_xml_parse_quick (const char *name, const char *dtd_name,
		     const struct gdb_xml_element *elements,
		     const char *document, void *user_data)
{
  gdb_xml_parser parser (name, elements, user_data);
  if (dtd_name != NULL)
    parser.use_dtd (dtd_name);
  return parser.parse (document);
}

/* Parse a field VALSTR that we expect to contain an integer value.
   The integer is returned in *VALP.  The string is parsed with an
   equivalent to strtoul.

   Returns 0 for success, -1 for error.  */

static int
xml_parse_unsigned_integer (const char *valstr, ULONGEST *valp)
{
  const char *endptr;
  ULONGEST result;

  if (*valstr == '\0')
    return -1;

  result = strtoulst (valstr, &endptr, 0);
  if (*endptr != '\0')
    return -1;

  *valp = result;
  return 0;
}

/* Parse an integer string into a ULONGEST and return it, or call
   gdb_xml_error if it could not be parsed.  */

ULONGEST
gdb_xml_parse_ulongest (struct gdb_xml_parser *parser, const char *value)
{
  ULONGEST result;

  if (xml_parse_unsigned_integer (value, &result) != 0)
    gdb_xml_error (parser, _("Can't convert \"%s\" to an integer"), value);

  return result;
}

/* Parse an integer attribute into a ULONGEST.  */

void *
gdb_xml_parse_attr_ulongest (struct gdb_xml_parser *parser,
			     const struct gdb_xml_attribute *attribute,
			     const char *value)
{
  ULONGEST result;
  void *ret;

  if (xml_parse_unsigned_integer (value, &result) != 0)
    gdb_xml_error (parser, _("Can't convert %s=\"%s\" to an integer"),
		   attribute->name, value);

  ret = XNEW (ULONGEST);
  memcpy (ret, &result, sizeof (result));
  return ret;
}

/* A handler_data for yes/no boolean values.  */

const struct gdb_xml_enum gdb_xml_enums_boolean[] = {
  { "yes", 1 },
  { "no", 0 },
  { NULL, 0 }
};

/* Map NAME to VALUE.  A struct gdb_xml_enum * should be saved as the
   value of handler_data when using gdb_xml_parse_attr_enum to parse a
   fixed list of possible strings.  The list is terminated by an entry
   with NAME == NULL.  */

void *
gdb_xml_parse_attr_enum (struct gdb_xml_parser *parser,
			 const struct gdb_xml_attribute *attribute,
			 const char *value)
{
  const struct gdb_xml_enum *enums
    = (const struct gdb_xml_enum *) attribute->handler_data;
  void *ret;

  for (enums = (const struct gdb_xml_enum *) attribute->handler_data;
       enums->name != NULL; enums++)
    if (strcasecmp (enums->name, value) == 0)
      break;

  if (enums->name == NULL)
    gdb_xml_error (parser, _("Unknown attribute value %s=\"%s\""),
		 attribute->name, value);

  ret = xmalloc (sizeof (enums->value));
  memcpy (ret, &enums->value, sizeof (enums->value));
  return ret;
}


/* XInclude processing.  This is done as a separate step from actually
   parsing the document, so that we can produce a single combined XML
   document - e.g. to hand to a front end or to simplify comparing two
   documents.  We make extensive use of XML_DefaultCurrent, to pass
   input text directly into the output without reformatting or
   requoting it.

   We output the DOCTYPE declaration for the first document unchanged,
   if present, and discard DOCTYPEs from included documents.  Only the
   one we pass through here is used when we feed the result back to
   expat.  The XInclude standard explicitly does not discuss
   validation of the result; we choose to apply the same DTD applied
   to the outermost document.

   We can not simply include the external DTD subset in the document
   as an internal subset, because <!IGNORE> and <!INCLUDE> are valid
   only in external subsets.  But if we do not pass the DTD into the
   output at all, default values will not be filled in.

   We don't pass through any <?xml> declaration because we generate
   UTF-8, not whatever the input encoding was.  */

struct xinclude_parsing_data
{
  xinclude_parsing_data (std::string &output_,
			 xml_fetch_another fetcher_, void *fetcher_baton_,
			 int include_depth_)
    : output (output_),
      skip_depth (0),
      include_depth (include_depth_),
      fetcher (fetcher_),
      fetcher_baton (fetcher_baton_)
  {}

  /* Where the output goes.  */
  std::string &output;

  /* A count indicating whether we are in an element whose
     children should not be copied to the output, and if so,
     how deep we are nested.  This is used for anything inside
     an xi:include, and for the DTD.  */
  int skip_depth;

  /* The number of <xi:include> elements currently being processed,
     to detect loops.  */
  int include_depth;

  /* A function to call to obtain additional features, and its
     baton.  */
  xml_fetch_another fetcher;
  void *fetcher_baton;
};

static void
xinclude_start_include (struct gdb_xml_parser *parser,
			const struct gdb_xml_element *element,
			void *user_data,
			std::vector<gdb_xml_value> &attributes)
{
  struct xinclude_parsing_data *data
    = (struct xinclude_parsing_data *) user_data;
  char *href = (char *) xml_find_attribute (attributes, "href")->value.get ();

  gdb_xml_debug (parser, _("Processing XInclude of \"%s\""), href);

  if (data->include_depth > MAX_XINCLUDE_DEPTH)
    gdb_xml_error (parser, _("Maximum XInclude depth (%d) exceeded"),
		   MAX_XINCLUDE_DEPTH);

  gdb::optional<gdb::char_vector> text
    = data->fetcher (href, data->fetcher_baton);
  if (!text)
    gdb_xml_error (parser, _("Could not load XML document \"%s\""), href);

  if (!xml_process_xincludes (data->output, parser->name (),
			      text->data (), data->fetcher,
			      data->fetcher_baton,
			      data->include_depth + 1))
    gdb_xml_error (parser, _("Parsing \"%s\" failed"), href);

  data->skip_depth++;
}

static void
xinclude_end_include (struct gdb_xml_parser *parser,
		      const struct gdb_xml_element *element,
		      void *user_data, const char *body_text)
{
  struct xinclude_parsing_data *data
    = (struct xinclude_parsing_data *) user_data;

  data->skip_depth--;
}

static void XMLCALL
xml_xinclude_default (void *data_, const XML_Char *s, int len)
{
  struct gdb_xml_parser *parser = (struct gdb_xml_parser *) data_;
  xinclude_parsing_data *data = (xinclude_parsing_data *) parser->user_data ();

  /* If we are inside of e.g. xi:include or the DTD, don't save this
     string.  */
  if (data->skip_depth)
    return;

  /* Otherwise just add it to the end of the document we're building
     up.  */
  data->output.append (s, len);
}

static void XMLCALL
xml_xinclude_start_doctype (void *data_, const XML_Char *doctypeName,
			    const XML_Char *sysid, const XML_Char *pubid,
			    int has_internal_subset)
{
  struct gdb_xml_parser *parser = (struct gdb_xml_parser *) data_;
  xinclude_parsing_data *data = (xinclude_parsing_data *) parser->user_data ();

  /* Don't print out the doctype, or the contents of the DTD internal
     subset, if any.  */
  data->skip_depth++;
}

static void XMLCALL
xml_xinclude_end_doctype (void *data_)
{
  struct gdb_xml_parser *parser = (struct gdb_xml_parser *) data_;
  xinclude_parsing_data *data = (xinclude_parsing_data *) parser->user_data ();

  data->skip_depth--;
}

static void XMLCALL
xml_xinclude_xml_decl (void *data_, const XML_Char *version,
		       const XML_Char *encoding, int standalone)
{
  /* Do nothing - this function prevents the default handler from
     being called, thus suppressing the XML declaration from the
     output.  */
}

const struct gdb_xml_attribute xinclude_attributes[] = {
  { "href", GDB_XML_AF_NONE, NULL, NULL },
  { NULL, GDB_XML_AF_NONE, NULL, NULL }
};

const struct gdb_xml_element xinclude_elements[] = {
  { "http://www.w3.org/2001/XInclude!include", xinclude_attributes, NULL,
    GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
    xinclude_start_include, xinclude_end_include },
  { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
};

/* The main entry point for <xi:include> processing.  */

bool
xml_process_xincludes (std::string &result,
		       const char *name, const char *text,
		       xml_fetch_another fetcher, void *fetcher_baton,
		       int depth)
{
  xinclude_parsing_data data (result, fetcher, fetcher_baton, depth);

  gdb_xml_parser parser (name, xinclude_elements, &data);
  parser.set_is_xinclude (true);

  XML_SetCharacterDataHandler (parser.expat_parser (), NULL);
  XML_SetDefaultHandler (parser.expat_parser (), xml_xinclude_default);

  /* Always discard the XML version declarations; the only important
     thing this provides is encoding, and our result will have been
     converted to UTF-8.  */
  XML_SetXmlDeclHandler (parser.expat_parser (), xml_xinclude_xml_decl);

  if (depth > 0)
    /* Discard the doctype for included documents.  */
    XML_SetDoctypeDeclHandler (parser.expat_parser (),
			       xml_xinclude_start_doctype,
			       xml_xinclude_end_doctype);

  parser.use_dtd ("xinclude.dtd");

  if (parser.parse (text) == 0)
    {
      if (depth == 0)
	gdb_xml_debug (&parser, _("XInclude processing succeeded."));
      return true;
    }

  return false;
}
#endif /* HAVE_LIBEXPAT */


/* Return an XML document which was compiled into GDB, from
   the given FILENAME, or NULL if the file was not compiled in.  */

const char *
fetch_xml_builtin (const char *filename)
{
  const char *(*p)[2];

  for (p = xml_builtin; (*p)[0]; p++)
    if (strcmp ((*p)[0], filename) == 0)
      return (*p)[1];

  return NULL;
}

/* A to_xfer_partial helper function which reads XML files which were
   compiled into GDB.  The target may call this function from its own
   to_xfer_partial handler, after converting object and annex to the
   appropriate filename.  */

LONGEST
xml_builtin_xfer_partial (const char *filename,
			  gdb_byte *readbuf, const gdb_byte *writebuf,
			  ULONGEST offset, LONGEST len)
{
  const char *buf;
  LONGEST len_avail;

  gdb_assert (readbuf != NULL && writebuf == NULL);
  gdb_assert (filename != NULL);

  buf = fetch_xml_builtin (filename);
  if (buf == NULL)
    return -1;

  len_avail = strlen (buf);
  if (offset >= len_avail)
    return 0;

  if (len > len_avail - offset)
    len = len_avail - offset;
  memcpy (readbuf, buf + offset, len);
  return len;
}


static void
show_debug_xml (struct ui_file *file, int from_tty,
		struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("XML debugging is %s.\n"), value);
}

gdb::optional<gdb::char_vector>
xml_fetch_content_from_file (const char *filename, void *baton)
{
  const char *dirname = (const char *) baton;
  gdb_file_up file;

  if (dirname && *dirname)
    {
      char *fullname = concat (dirname, "/", filename, (char *) NULL);

      if (fullname == NULL)
	malloc_failure (0);
      file = gdb_fopen_cloexec (fullname, FOPEN_RT);
      xfree (fullname);
    }
  else
    file = gdb_fopen_cloexec (filename, FOPEN_RT);

  if (file == NULL)
    return {};

  /* Read in the whole file.  */

  size_t len;

  if (fseek (file.get (), 0, SEEK_END) == -1)
    perror_with_name (_("seek to end of file"));
  len = ftell (file.get ());
  rewind (file.get ());

  gdb::char_vector text (len + 1);

  if (fread (text.data (), 1, len, file.get ()) != len
      || ferror (file.get ()))
    {
      warning (_("Read error from \"%s\""), filename);
      return {};
    }

  text.back () = '\0';
  return text;
}

void
_initialize_xml_support (void)
{
  add_setshow_boolean_cmd ("xml", class_maintenance, &debug_xml,
			   _("Set XML parser debugging."),
			   _("Show XML parser debugging."),
			   _("When set, debugging messages for XML parsers "
			     "are displayed."),
			   NULL, show_debug_xml,
			   &setdebuglist, &showdebuglist);
}