aboutsummaryrefslogtreecommitdiff
path: root/gdb/macroexp.c
blob: 6bd5ef513fd2d3c8c18efd54e91f3043c3ffd54c (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
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
/* C preprocessor macro expansion for GDB.
   Copyright (C) 2002-2022 Free Software Foundation, Inc.
   Contributed by Red Hat, 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 "gdbsupport/gdb_obstack.h"
#include "macrotab.h"
#include "macroexp.h"
#include "macroscope.h"
#include "c-lang.h"




/* A string type that we can use to refer to substrings of other
   strings.  */

struct shared_macro_buffer
{
  /* An array of characters.  This buffer is a pointer into some
     larger string and thus we can't assume in that the text is
     null-terminated.  */
  const char *text;

  /* The number of characters in the string.  */
  int len;

  /* For detecting token splicing. 

     This is the index in TEXT of the first character of the token
     that abuts the end of TEXT.  If TEXT contains no tokens, then we
     set this equal to LEN.  If TEXT ends in whitespace, then there is
     no token abutting the end of TEXT (it's just whitespace), and
     again, we set this equal to LEN.  We set this to -1 if we don't
     know the nature of TEXT.  */
  int last_token = -1;

  /* If this buffer is holding the result from get_token, then this 
     is non-zero if it is an identifier token, zero otherwise.  */
  int is_identifier = 0;

  shared_macro_buffer ()
    : text (NULL),
      len (0)
  {
  }

  /* Set the macro buffer to refer to the LEN bytes at ADDR, as a
     shared substring.  */
  shared_macro_buffer (const char *addr, int len)
  {
    set_shared (addr, len);
  }

  /* Set the macro buffer to refer to the LEN bytes at ADDR, as a
     shared substring.  */
  void set_shared (const char *addr, int len_)
  {
    text = addr;
    len = len_;
  }
};

/* A string type that we can resize and quickly append to.  */

struct growable_macro_buffer
{
  /* An array of characters.  The first LEN bytes are the real text,
     but there are SIZE bytes allocated to the array.  */
  char *text;

  /* The number of characters in the string.  */
  int len;

  /* The number of characters allocated to the string.  */
  int size;

  /* For detecting token splicing.

     This is the index in TEXT of the first character of the token
     that abuts the end of TEXT.  If TEXT contains no tokens, then we
     set this equal to LEN.  If TEXT ends in whitespace, then there is
     no token abutting the end of TEXT (it's just whitespace), and
     again, we set this equal to LEN.  We set this to -1 if we don't
     know the nature of TEXT.  */
  int last_token = -1;

  /* Set the macro buffer to the empty string, guessing that its
     final contents will fit in N bytes.  (It'll get resized if it
     doesn't, so the guess doesn't have to be right.)  Allocate the
     initial storage with xmalloc.  */
  explicit growable_macro_buffer (int n)
    : len (0),
      size (n)
  {
    if (n > 0)
      text = (char *) xmalloc (n);
    else
      text = NULL;
  }

  DISABLE_COPY_AND_ASSIGN (growable_macro_buffer);

  ~growable_macro_buffer ()
  {
    xfree (text);
  }

  /* Release the text of the buffer to the caller.  */
  gdb::unique_xmalloc_ptr<char> release ()
  {
    gdb_assert (size);
    char *result = text;
    text = NULL;
    return gdb::unique_xmalloc_ptr<char> (result);
  }

  /* Resize the buffer to be at least N bytes long.  */
  void resize_buffer (int n)
  {
    if (size == 0)
      size = n;
    else
      while (size <= n)
	size *= 2;

    text = (char *) xrealloc (text, size);
  }

  /* Append the character C to the buffer.  */
  void appendc (int c)
  {
    int new_len = len + 1;

    if (new_len > size)
      resize_buffer (new_len);

    text[len] = c;
    len = new_len;
  }

  /* Append the COUNT bytes at ADDR to the buffer.  */
  void appendmem (const char *addr, int count)
  {
    int new_len = len + count;

    if (new_len > size)
      resize_buffer (new_len);

    memcpy (text + len, addr, count);
    len = new_len;
  }
};



/* Recognizing preprocessor tokens.  */


int
macro_is_whitespace (int c)
{
  return (c == ' '
	  || c == '\t'
	  || c == '\n'
	  || c == '\v'
	  || c == '\f');
}


int
macro_is_digit (int c)
{
  return ('0' <= c && c <= '9');
}


int
macro_is_identifier_nondigit (int c)
{
  return (c == '_'
	  || ('a' <= c && c <= 'z')
	  || ('A' <= c && c <= 'Z'));
}


static void
set_token (shared_macro_buffer *tok, const char *start, const char *end)
{
  tok->set_shared (start, end - start);
  tok->last_token = 0;

  /* Presumed; get_identifier may overwrite this.  */
  tok->is_identifier = 0;
}


static int
get_comment (shared_macro_buffer *tok, const char *p, const char *end)
{
  if (p + 2 > end)
    return 0;
  else if (p[0] == '/'
	   && p[1] == '*')
    {
      const char *tok_start = p;

      p += 2;

      for (; p < end; p++)
	if (p + 2 <= end
	    && p[0] == '*'
	    && p[1] == '/')
	  {
	    p += 2;
	    set_token (tok, tok_start, p);
	    return 1;
	  }

      error (_("Unterminated comment in macro expansion."));
    }
  else if (p[0] == '/'
	   && p[1] == '/')
    {
      const char *tok_start = p;

      p += 2;
      for (; p < end; p++)
	if (*p == '\n')
	  break;

      set_token (tok, tok_start, p);
      return 1;
    }
  else
    return 0;
}


static int
get_identifier (shared_macro_buffer *tok, const char *p, const char *end)
{
  if (p < end
      && macro_is_identifier_nondigit (*p))
    {
      const char *tok_start = p;

      while (p < end
	     && (macro_is_identifier_nondigit (*p)
		 || macro_is_digit (*p)))
	p++;

      set_token (tok, tok_start, p);
      tok->is_identifier = 1;
      return 1;
    }
  else
    return 0;
}


static int
get_pp_number (shared_macro_buffer *tok, const char *p, const char *end)
{
  if (p < end
      && (macro_is_digit (*p)
	  || (*p == '.'
	      && p + 2 <= end
	      && macro_is_digit (p[1]))))
    {
      const char *tok_start = p;

      while (p < end)
	{
	  if (p + 2 <= end
	      && strchr ("eEpP", *p)
	      && (p[1] == '+' || p[1] == '-'))
	    p += 2;
	  else if (macro_is_digit (*p)
		   || macro_is_identifier_nondigit (*p)
		   || *p == '.')
	    p++;
	  else
	    break;
	}

      set_token (tok, tok_start, p);
      return 1;
    }
  else
    return 0;
}



/* If the text starting at P going up to (but not including) END
   starts with a character constant, set *TOK to point to that
   character constant, and return 1.  Otherwise, return zero.
   Signal an error if it contains a malformed or incomplete character
   constant.  */
static int
get_character_constant (shared_macro_buffer *tok,
			const char *p, const char *end)
{
  /* ISO/IEC 9899:1999 (E)  Section 6.4.4.4  paragraph 1 
     But of course, what really matters is that we handle it the same
     way GDB's C/C++ lexer does.  So we call parse_escape in utils.c
     to handle escape sequences.  */
  if ((p + 1 <= end && *p == '\'')
      || (p + 2 <= end
	  && (p[0] == 'L' || p[0] == 'u' || p[0] == 'U')
	  && p[1] == '\''))
    {
      const char *tok_start = p;
      int char_count = 0;

      if (*p == '\'')
	p++;
      else if (*p == 'L' || *p == 'u' || *p == 'U')
	p += 2;
      else
	gdb_assert_not_reached ("unexpected character constant");

      for (;;)
	{
	  if (p >= end)
	    error (_("Unmatched single quote."));
	  else if (*p == '\'')
	    {
	      if (!char_count)
		error (_("A character constant must contain at least one "
		       "character."));
	      p++;
	      break;
	    }
	  else if (*p == '\\')
	    {
	      const char *s, *o;

	      s = o = ++p;
	      char_count += c_parse_escape (&s, NULL);
	      p += s - o;
	    }
	  else
	    {
	      p++;
	      char_count++;
	    }
	}

      set_token (tok, tok_start, p);
      return 1;
    }
  else
    return 0;
}


/* If the text starting at P going up to (but not including) END
   starts with a string literal, set *TOK to point to that string
   literal, and return 1.  Otherwise, return zero.  Signal an error if
   it contains a malformed or incomplete string literal.  */
static int
get_string_literal (shared_macro_buffer *tok, const char *p, const char *end)
{
  if ((p + 1 <= end
       && *p == '"')
      || (p + 2 <= end
	  && (p[0] == 'L' || p[0] == 'u' || p[0] == 'U')
	  && p[1] == '"'))
    {
      const char *tok_start = p;

      if (*p == '"')
	p++;
      else if (*p == 'L' || *p == 'u' || *p == 'U')
	p += 2;
      else
	gdb_assert_not_reached ("unexpected string literal");

      for (;;)
	{
	  if (p >= end)
	    error (_("Unterminated string in expression."));
	  else if (*p == '"')
	    {
	      p++;
	      break;
	    }
	  else if (*p == '\n')
	    error (_("Newline characters may not appear in string "
		   "constants."));
	  else if (*p == '\\')
	    {
	      const char *s, *o;

	      s = o = ++p;
	      c_parse_escape (&s, NULL);
	      p += s - o;
	    }
	  else
	    p++;
	}

      set_token (tok, tok_start, p);
      return 1;
    }
  else
    return 0;
}


static int
get_punctuator (shared_macro_buffer *tok, const char *p, const char *end)
{
  /* Here, speed is much less important than correctness and clarity.  */

  /* ISO/IEC 9899:1999 (E)  Section 6.4.6  Paragraph 1.
     Note that this table is ordered in a special way.  A punctuator
     which is a prefix of another punctuator must appear after its
     "extension".  Otherwise, the wrong token will be returned.  */
  static const char * const punctuators[] = {
    "[", "]", "(", ")", "{", "}", "?", ";", ",", "~",
    "...", ".",
    "->", "--", "-=", "-",
    "++", "+=", "+",
    "*=", "*",
    "!=", "!",
    "&&", "&=", "&",
    "/=", "/",
    "%>", "%:%:", "%:", "%=", "%",
    "^=", "^",
    "##", "#",
    ":>", ":",
    "||", "|=", "|",
    "<<=", "<<", "<=", "<:", "<%", "<",
    ">>=", ">>", ">=", ">",
    "==", "=",
    0
  };

  int i;

  if (p + 1 <= end)
    {
      for (i = 0; punctuators[i]; i++)
	{
	  const char *punctuator = punctuators[i];

	  if (p[0] == punctuator[0])
	    {
	      int len = strlen (punctuator);

	      if (p + len <= end
		  && ! memcmp (p, punctuator, len))
		{
		  set_token (tok, p, p + len);
		  return 1;
		}
	    }
	}
    }

  return 0;
}


/* Peel the next preprocessor token off of SRC, and put it in TOK.
   Mutate TOK to refer to the first token in SRC, and mutate SRC to
   refer to the text after that token.  The resulting TOK will point
   into the same string SRC does.  Initialize TOK's last_token field.
   Return non-zero if we succeed, or 0 if we didn't find any more
   tokens in SRC.  */

static int
get_token (shared_macro_buffer *tok, shared_macro_buffer *src)
{
  const char *p = src->text;
  const char *end = p + src->len;

  /* From the ISO C standard, ISO/IEC 9899:1999 (E), section 6.4:

     preprocessing-token: 
	 header-name
	 identifier
	 pp-number
	 character-constant
	 string-literal
	 punctuator
	 each non-white-space character that cannot be one of the above

     We don't have to deal with header-name tokens, since those can
     only occur after a #include, which we will never see.  */

  while (p < end)
    if (macro_is_whitespace (*p))
      p++;
    else if (get_comment (tok, p, end))
      p += tok->len;
    else if (get_pp_number (tok, p, end)
	     || get_character_constant (tok, p, end)
	     || get_string_literal (tok, p, end)
	     /* Note: the grammar in the standard seems to be
		ambiguous: L'x' can be either a wide character
		constant, or an identifier followed by a normal
		character constant.  By trying `get_identifier' after
		we try get_character_constant and get_string_literal,
		we give the wide character syntax precedence.  Now,
		since GDB doesn't handle wide character constants
		anyway, is this the right thing to do?  */
	     || get_identifier (tok, p, end)
	     || get_punctuator (tok, p, end))
      {
	/* How many characters did we consume, including whitespace?  */
	int consumed = p - src->text + tok->len;

	src->text += consumed;
	src->len -= consumed;
	return 1;
      }
    else 
      {
	/* We have found a "non-whitespace character that cannot be
	   one of the above."  Make a token out of it.  */
	int consumed;

	set_token (tok, p, p + 1);
	consumed = p - src->text + tok->len;
	src->text += consumed;
	src->len -= consumed;
	return 1;
      }

  return 0;
}



/* Appending token strings, with and without splicing  */


/* Append the macro buffer SRC to the end of DEST, and ensure that
   doing so doesn't splice the token at the end of SRC with the token
   at the beginning of DEST.  SRC and DEST must have their last_token
   fields set.  Upon return, DEST's last_token field is set correctly.

   For example:

   If DEST is "(" and SRC is "y", then we can return with
   DEST set to "(y" --- we've simply appended the two buffers.

   However, if DEST is "x" and SRC is "y", then we must not return
   with DEST set to "xy" --- that would splice the two tokens "x" and
   "y" together to make a single token "xy".  However, it would be
   fine to return with DEST set to "x y".  Similarly, "<" and "<" must
   yield "< <", not "<<", etc.  */
static void
append_tokens_without_splicing (growable_macro_buffer *dest,
                                shared_macro_buffer *src)
{
  int original_dest_len = dest->len;
  shared_macro_buffer dest_tail, new_token;

  gdb_assert (src->last_token != -1);
  gdb_assert (dest->last_token != -1);
  
  /* First, just try appending the two, and call get_token to see if
     we got a splice.  */
  dest->appendmem (src->text, src->len);

  /* If DEST originally had no token abutting its end, then we can't
     have spliced anything, so we're done.  */
  if (dest->last_token == original_dest_len)
    {
      dest->last_token = original_dest_len + src->last_token;
      return;
    }

  /* Set DEST_TAIL to point to the last token in DEST, followed by
     all the stuff we just appended.  */
  dest_tail.set_shared (dest->text + dest->last_token,
			dest->len - dest->last_token);

  /* Re-parse DEST's last token.  We know that DEST used to contain
     at least one token, so if it doesn't contain any after the
     append, then we must have spliced "/" and "*" or "/" and "/" to
     make a comment start.  (Just for the record, I got this right
     the first time.  This is not a bug fix.)  */
  if (get_token (&new_token, &dest_tail)
      && (new_token.text + new_token.len
	  == dest->text + original_dest_len))
    {
      /* No splice, so we're done.  */
      dest->last_token = original_dest_len + src->last_token;
      return;
    }

  /* Okay, a simple append caused a splice.  Let's chop dest back to
     its original length and try again, but separate the texts with a
     space.  */
  dest->len = original_dest_len;
  dest->appendc (' ');
  dest->appendmem (src->text, src->len);

  dest_tail.set_shared (dest->text + dest->last_token,
			dest->len - dest->last_token);

  /* Try to re-parse DEST's last token, as above.  */
  if (get_token (&new_token, &dest_tail)
      && (new_token.text + new_token.len
	  == dest->text + original_dest_len))
    {
      /* No splice, so we're done.  */
      dest->last_token = original_dest_len + 1 + src->last_token;
      return;
    }

  /* As far as I know, there's no case where inserting a space isn't
     enough to prevent a splice.  */
  internal_error (_("unable to avoid splicing tokens during macro expansion"));
}

/* Stringify an argument, and insert it into DEST.  ARG is the text to
   stringify; it is LEN bytes long.  */

static void
stringify (growable_macro_buffer *dest, const char *arg, int len)
{
  /* Trim initial whitespace from ARG.  */
  while (len > 0 && macro_is_whitespace (*arg))
    {
      ++arg;
      --len;
    }

  /* Trim trailing whitespace from ARG.  */
  while (len > 0 && macro_is_whitespace (arg[len - 1]))
    --len;

  /* Insert the string.  */
  dest->appendc ('"');
  while (len > 0)
    {
      /* We could try to handle strange cases here, like control
	 characters, but there doesn't seem to be much point.  */
      if (macro_is_whitespace (*arg))
	{
	  /* Replace a sequence of whitespace with a single space.  */
	  dest->appendc (' ');
	  while (len > 1 && macro_is_whitespace (arg[1]))
	    {
	      ++arg;
	      --len;
	    }
	}
      else if (*arg == '\\' || *arg == '"')
	{
	  dest->appendc ('\\');
	  dest->appendc (*arg);
	}
      else
	dest->appendc (*arg);
      ++arg;
      --len;
    }
  dest->appendc ('"');
  dest->last_token = dest->len;
}

/* See macroexp.h.  */

gdb::unique_xmalloc_ptr<char>
macro_stringify (const char *str)
{
  int len = strlen (str);
  growable_macro_buffer buffer (len);

  stringify (&buffer, str, len);
  buffer.appendc ('\0');

  return buffer.release ();
}


/* Expanding macros!  */


/* A singly-linked list of the names of the macros we are currently 
   expanding --- for detecting expansion loops.  */
struct macro_name_list {
  const char *name;
  struct macro_name_list *next;
};


/* Return non-zero if we are currently expanding the macro named NAME,
   according to LIST; otherwise, return zero.

   You know, it would be possible to get rid of all the NO_LOOP
   arguments to these functions by simply generating a new lookup
   function and baton which refuses to find the definition for a
   particular macro, and otherwise delegates the decision to another
   function/baton pair.  But that makes the linked list of excluded
   macros chained through untyped baton pointers, which will make it
   harder to debug.  :(  */
static int
currently_rescanning (struct macro_name_list *list, const char *name)
{
  for (; list; list = list->next)
    if (strcmp (name, list->name) == 0)
      return 1;

  return 0;
}


/* Gather the arguments to a macro expansion.

   NAME is the name of the macro being invoked.  (It's only used for
   printing error messages.)

   Assume that SRC is the text of the macro invocation immediately
   following the macro name.  For example, if we're processing the
   text foo(bar, baz), then NAME would be foo and SRC will be (bar,
   baz).

   If SRC doesn't start with an open paren ( token at all, return
   false, leave SRC unchanged, and don't set *ARGS_PTR to anything.

   If SRC doesn't contain a properly terminated argument list, then
   raise an error.

   For a variadic macro, NARGS holds the number of formal arguments to
   the macro.  For a GNU-style variadic macro, this should be the
   number of named arguments.  For a non-variadic macro, NARGS should
   be -1.

   Otherwise, return true and set *ARGS_PTR to a vector of macro
   buffers referring to the argument texts.  The macro buffers share
   their text with SRC, and their last_token fields are initialized.

   NOTE WELL: if SRC starts with a open paren ( token followed
   immediately by a close paren ) token (e.g., the invocation looks
   like "foo()"), we treat that as one argument, which happens to be
   the empty list of tokens.  The caller should keep in mind that such
   a sequence of tokens is a valid way to invoke one-parameter
   function-like macros, but also a valid way to invoke zero-parameter
   function-like macros.  Eeew.

   Consume the tokens from SRC; after this call, SRC contains the text
   following the invocation.  */

static bool
gather_arguments (const char *name, shared_macro_buffer *src, int nargs,
		  std::vector<shared_macro_buffer> *args_ptr)
{
  shared_macro_buffer tok;
  std::vector<shared_macro_buffer> args;

  /* Does SRC start with an opening paren token?  Read from a copy of
     SRC, so SRC itself is unaffected if we don't find an opening
     paren.  */
  {
    shared_macro_buffer temp (src->text, src->len);

    if (! get_token (&tok, &temp)
	|| tok.len != 1
	|| tok.text[0] != '(')
      return false;
  }

  /* Consume SRC's opening paren.  */
  get_token (&tok, src);

  for (;;)
    {
      shared_macro_buffer *arg;
      int depth;

      /* Initialize the next argument.  */
      args.emplace_back ();
      arg = &args.back ();
      set_token (arg, src->text, src->text);

      /* Gather the argument's tokens.  */
      depth = 0;
      for (;;)
	{
	  if (! get_token (&tok, src))
	    error (_("Malformed argument list for macro `%s'."), name);

	  /* Is tok an opening paren?  */
	  if (tok.len == 1 && tok.text[0] == '(')
	    depth++;

	  /* Is tok is a closing paren?  */
	  else if (tok.len == 1 && tok.text[0] == ')')
	    {
	      /* If it's a closing paren at the top level, then that's
		 the end of the argument list.  */
	      if (depth == 0)
		{
		  /* In the varargs case, the last argument may be
		     missing.  Add an empty argument in this case.  */
		  if (nargs != -1 && args.size () == nargs - 1)
		    {
		      args.emplace_back ();
		      arg = &args.back ();
		      set_token (arg, src->text, src->text);
		    }

		  *args_ptr = std::move (args);
		  return true;
		}

	      depth--;
	    }

	  /* If tok is a comma at top level, then that's the end of
	     the current argument.  However, if we are handling a
	     variadic macro and we are computing the last argument, we
	     want to include the comma and remaining tokens.  */
	  else if (tok.len == 1 && tok.text[0] == ',' && depth == 0
		   && (nargs == -1 || args.size () < nargs))
	    break;

	  /* Extend the current argument to enclose this token.  If
	     this is the current argument's first token, leave out any
	     leading whitespace, just for aesthetics.  */
	  if (arg->len == 0)
	    {
	      arg->text = tok.text;
	      arg->len = tok.len;
	      arg->last_token = 0;
	    }
	  else
	    {
	      arg->len = (tok.text + tok.len) - arg->text;
	      arg->last_token = tok.text - arg->text;
	    }
	}
    }
}


/* The `expand' and `substitute_args' functions both invoke `scan'
   recursively, so we need a forward declaration somewhere.  */
static void scan (growable_macro_buffer *dest,
		  shared_macro_buffer *src,
		  struct macro_name_list *no_loop,
		  const macro_scope &scope);

/* A helper function for substitute_args.
   
   ARGV is a vector of all the arguments; ARGC is the number of
   arguments.  IS_VARARGS is true if the macro being substituted is a
   varargs macro; in this case VA_ARG_NAME is the name of the
   "variable" argument.  VA_ARG_NAME is ignored if IS_VARARGS is
   false.

   If the token TOK is the name of a parameter, return the parameter's
   index.  If TOK is not an argument, return -1.  */

static int
find_parameter (const shared_macro_buffer *tok,
		int is_varargs, const shared_macro_buffer *va_arg_name,
		int argc, const char * const *argv)
{
  int i;

  if (! tok->is_identifier)
    return -1;

  for (i = 0; i < argc; ++i)
    if (tok->len == strlen (argv[i]) 
	&& !memcmp (tok->text, argv[i], tok->len))
      return i;

  if (is_varargs && tok->len == va_arg_name->len
      && ! memcmp (tok->text, va_arg_name->text, tok->len))
    return argc - 1;

  return -1;
}
 
/* Helper function for substitute_args that gets the next token and
   updates the passed-in state variables.  */

static void
get_next_token_for_substitution (shared_macro_buffer *replacement_list,
				 shared_macro_buffer *token,
				 const char **start,
				 shared_macro_buffer *lookahead,
				 const char **lookahead_start,
				 int *lookahead_valid,
				 bool *keep_going)
{
  if (!*lookahead_valid)
    *keep_going = false;
  else
    {
      *keep_going = true;
      *token = *lookahead;
      *start = *lookahead_start;
      *lookahead_start = replacement_list->text;
      *lookahead_valid = get_token (lookahead, replacement_list);
    }
}

/* Given the macro definition DEF, being invoked with the actual
   arguments given by ARGV, substitute the arguments into the
   replacement list, and store the result in DEST.

   IS_VARARGS should be true if DEF is a varargs macro.  In this case,
   VA_ARG_NAME should be the name of the "variable" argument -- either
   __VA_ARGS__ for c99-style varargs, or the final argument name, for
   GNU-style varargs.  If IS_VARARGS is false, this parameter is
   ignored.

   If it is necessary to expand macro invocations in one of the
   arguments, use LOOKUP_FUNC and LOOKUP_BATON to find the macro
   definitions, and don't expand invocations of the macros listed in
   NO_LOOP.  */

static void
substitute_args (growable_macro_buffer *dest,
		 struct macro_definition *def,
		 int is_varargs, const shared_macro_buffer *va_arg_name,
		 const std::vector<shared_macro_buffer> &argv,
		 struct macro_name_list *no_loop,
		 const macro_scope &scope)
{
  /* The token we are currently considering.  */
  shared_macro_buffer tok;
  /* The replacement list's pointer from just before TOK was lexed.  */
  const char *original_rl_start;
  /* We have a single lookahead token to handle token splicing.  */
  shared_macro_buffer lookahead;
  /* The lookahead token might not be valid.  */
  int lookahead_valid;
  /* The replacement list's pointer from just before LOOKAHEAD was
     lexed.  */
  const char *lookahead_rl_start;

  /* A macro buffer for the macro's replacement list.  */
  shared_macro_buffer replacement_list (def->replacement,
					strlen (def->replacement));

  gdb_assert (dest->len == 0);
  dest->last_token = 0;

  original_rl_start = replacement_list.text;
  if (! get_token (&tok, &replacement_list))
    return;
  lookahead_rl_start = replacement_list.text;
  lookahead_valid = get_token (&lookahead, &replacement_list);

  /* __VA_OPT__ state variable.  The states are:
     0 - nothing happening
     1 - saw __VA_OPT__
     >= 2 in __VA_OPT__, the value encodes the parenthesis depth.  */
  unsigned vaopt_state = 0;

  for (bool keep_going = true;
       keep_going;
       get_next_token_for_substitution (&replacement_list,
					&tok,
					&original_rl_start,
					&lookahead,
					&lookahead_rl_start,
					&lookahead_valid,
					&keep_going))
    {
      bool token_is_vaopt = (tok.len == 10
			     && startswith (tok.text, "__VA_OPT__"));

      if (vaopt_state > 0)
	{
	  if (token_is_vaopt)
	    error (_("__VA_OPT__ cannot appear inside __VA_OPT__"));
	  else if (tok.len == 1 && tok.text[0] == '(')
	    {
	      ++vaopt_state;
	      /* We just entered __VA_OPT__, so don't emit this
		 token.  */
	      continue;
	    }
	  else if (vaopt_state == 1)
	    error (_("__VA_OPT__ must be followed by an open parenthesis"));
	  else if (tok.len == 1 && tok.text[0] == ')')
	    {
	      --vaopt_state;
	      if (vaopt_state == 1)
		{
		  /* Done with __VA_OPT__.  */
		  vaopt_state = 0;
		  /* Don't emit.  */
		  continue;
		}
	    }

	  /* If __VA_ARGS__ is empty, then drop the contents of
	     __VA_OPT__.  */
	  if (argv.back ().len == 0)
	    continue;
	}
      else if (token_is_vaopt)
	{
	  if (!is_varargs)
	    error (_("__VA_OPT__ is only valid in a variadic macro"));
	  vaopt_state = 1;
	  /* Don't emit this token.  */
	  continue;
	}

      /* Just for aesthetics.  If we skipped some whitespace, copy
	 that to DEST.  */
      if (tok.text > original_rl_start)
	{
	  dest->appendmem (original_rl_start, tok.text - original_rl_start);
	  dest->last_token = dest->len;
	}

      /* Is this token the stringification operator?  */
      if (tok.len == 1
	  && tok.text[0] == '#')
	{
	  int arg;

	  if (!lookahead_valid)
	    error (_("Stringification operator requires an argument."));

	  arg = find_parameter (&lookahead, is_varargs, va_arg_name,
				def->argc, def->argv);
	  if (arg == -1)
	    error (_("Argument to stringification operator must name "
		     "a macro parameter."));

	  stringify (dest, argv[arg].text, argv[arg].len);

	  /* Read one token and let the loop iteration code handle the
	     rest.  */
	  lookahead_rl_start = replacement_list.text;
	  lookahead_valid = get_token (&lookahead, &replacement_list);
	}
      /* Is this token the splicing operator?  */
      else if (tok.len == 2
	       && tok.text[0] == '#'
	       && tok.text[1] == '#')
	error (_("Stray splicing operator"));
      /* Is the next token the splicing operator?  */
      else if (lookahead_valid
	       && lookahead.len == 2
	       && lookahead.text[0] == '#'
	       && lookahead.text[1] == '#')
	{
	  int finished = 0;
	  int prev_was_comma = 0;

	  /* Note that GCC warns if the result of splicing is not a
	     token.  In the debugger there doesn't seem to be much
	     benefit from doing this.  */

	  /* Insert the first token.  */
	  if (tok.len == 1 && tok.text[0] == ',')
	    prev_was_comma = 1;
	  else
	    {
	      int arg = find_parameter (&tok, is_varargs, va_arg_name,
					def->argc, def->argv);

	      if (arg != -1)
		dest->appendmem (argv[arg].text, argv[arg].len);
	      else
		dest->appendmem (tok.text, tok.len);
	    }

	  /* Apply a possible sequence of ## operators.  */
	  for (;;)
	    {
	      if (! get_token (&tok, &replacement_list))
		error (_("Splicing operator at end of macro"));

	      /* Handle a comma before a ##.  If we are handling
		 varargs, and the token on the right hand side is the
		 varargs marker, and the final argument is empty or
		 missing, then drop the comma.  This is a GNU
		 extension.  There is one ambiguous case here,
		 involving pedantic behavior with an empty argument,
		 but we settle that in favor of GNU-style (GCC uses an
		 option).  If we aren't dealing with varargs, we
		 simply insert the comma.  */
	      if (prev_was_comma)
		{
		  if (! (is_varargs
			 && tok.len == va_arg_name->len
			 && !memcmp (tok.text, va_arg_name->text, tok.len)
			 && argv.back ().len == 0))
		    dest->appendmem (",", 1);
		  prev_was_comma = 0;
		}

	      /* Insert the token.  If it is a parameter, insert the
		 argument.  If it is a comma, treat it specially.  */
	      if (tok.len == 1 && tok.text[0] == ',')
		prev_was_comma = 1;
	      else
		{
		  int arg = find_parameter (&tok, is_varargs, va_arg_name,
					    def->argc, def->argv);

		  if (arg != -1)
		    dest->appendmem (argv[arg].text, argv[arg].len);
		  else
		    dest->appendmem (tok.text, tok.len);
		}

	      /* Now read another token.  If it is another splice, we
		 loop.  */
	      original_rl_start = replacement_list.text;
	      if (! get_token (&tok, &replacement_list))
		{
		  finished = 1;
		  break;
		}

	      if (! (tok.len == 2
		     && tok.text[0] == '#'
		     && tok.text[1] == '#'))
		break;
	    }

	  if (prev_was_comma)
	    {
	      /* We saw a comma.  Insert it now.  */
	      dest->appendmem (",", 1);
	    }

	  dest->last_token = dest->len;
	  if (finished)
	    lookahead_valid = 0;
	  else
	    {
	      /* Set up for the loop iterator.  */
	      lookahead = tok;
	      lookahead_rl_start = original_rl_start;
	      lookahead_valid = 1;
	    }
	}
      else
	{
	  /* Is this token an identifier?  */
	  int substituted = 0;
	  int arg = find_parameter (&tok, is_varargs, va_arg_name,
				    def->argc, def->argv);

	  if (arg != -1)
	    {
	      /* Expand any macro invocations in the argument text,
		 and append the result to dest.  Remember that scan
		 mutates its source, so we need to scan a new buffer
		 referring to the argument's text, not the argument
		 itself.  */
	      shared_macro_buffer arg_src (argv[arg].text, argv[arg].len);
	      scan (dest, &arg_src, no_loop, scope);
	      substituted = 1;
	    }

	  /* If it wasn't a parameter, then just copy it across.  */
	  if (! substituted)
	    append_tokens_without_splicing (dest, &tok);
	}
    }

  if (vaopt_state > 0)
    error (_("Unterminated __VA_OPT__"));
}


/* Expand a call to a macro named ID, whose definition is DEF.  Append
   its expansion to DEST.  SRC is the input text following the ID
   token.  We are currently rescanning the expansions of the macros
   named in NO_LOOP; don't re-expand them.  Use LOOKUP_FUNC and
   LOOKUP_BATON to find definitions for any nested macro references.

   Return 1 if we decided to expand it, zero otherwise.  (If it's a
   function-like macro name that isn't followed by an argument list,
   we don't expand it.)  If we return zero, leave SRC unchanged.  */
static int
expand (const char *id,
	struct macro_definition *def,
	growable_macro_buffer *dest,
	shared_macro_buffer *src,
	struct macro_name_list *no_loop,
	const macro_scope &scope)
{
  struct macro_name_list new_no_loop;

  /* Create a new node to be added to the front of the no-expand list.
     This list is appropriate for re-scanning replacement lists, but
     it is *not* appropriate for scanning macro arguments; invocations
     of the macro whose arguments we are gathering *do* get expanded
     there.  */
  new_no_loop.name = id;
  new_no_loop.next = no_loop;

  /* What kind of macro are we expanding?  */
  if (def->kind == macro_object_like)
    {
      shared_macro_buffer replacement_list (def->replacement,
					    strlen (def->replacement));

      scan (dest, &replacement_list, &new_no_loop, scope);
      return 1;
    }
  else if (def->kind == macro_function_like)
    {
      shared_macro_buffer va_arg_name;
      int is_varargs = 0;

      if (def->argc >= 1)
	{
	  if (strcmp (def->argv[def->argc - 1], "...") == 0)
	    {
	      /* In C99-style varargs, substitution is done using
		 __VA_ARGS__.  */
	      va_arg_name.set_shared ("__VA_ARGS__", strlen ("__VA_ARGS__"));
	      is_varargs = 1;
	    }
	  else
	    {
	      int len = strlen (def->argv[def->argc - 1]);

	      if (len > 3
		  && strcmp (def->argv[def->argc - 1] + len - 3, "...") == 0)
		{
		  /* In GNU-style varargs, the name of the
		     substitution parameter is the name of the formal
		     argument without the "...".  */
		  va_arg_name.set_shared (def->argv[def->argc - 1], len - 3);
		  is_varargs = 1;
		}
	    }
	}

      std::vector<shared_macro_buffer> argv;
      /* If we couldn't find any argument list, then we don't expand
	 this macro.  */
      if (!gather_arguments (id, src, is_varargs ? def->argc : -1,
			     &argv))
	return 0;

      /* Check that we're passing an acceptable number of arguments for
	 this macro.  */
      if (argv.size () != def->argc)
	{
	  if (is_varargs && argv.size () >= def->argc - 1)
	    {
	      /* Ok.  */
	    }
	  /* Remember that a sequence of tokens like "foo()" is a
	     valid invocation of a macro expecting either zero or one
	     arguments.  */
	  else if (! (argv.size () == 1
		      && argv[0].len == 0
		      && def->argc == 0))
	    error (_("Wrong number of arguments to macro `%s' "
		   "(expected %d, got %d)."),
		   id, def->argc, int (argv.size ()));
	}

      /* Note that we don't expand macro invocations in the arguments
	 yet --- we let subst_args take care of that.  Parameters that
	 appear as operands of the stringifying operator "#" or the
	 splicing operator "##" don't get macro references expanded,
	 so we can't really tell whether it's appropriate to macro-
	 expand an argument until we see how it's being used.  */
      growable_macro_buffer substituted (0);
      substitute_args (&substituted, def, is_varargs, &va_arg_name,
		       argv, no_loop, scope);

      /* Now `substituted' is the macro's replacement list, with all
	 argument values substituted into it properly.	Re-scan it for
	 macro references, but don't expand invocations of this macro.

	 We create a new buffer, `substituted_src', which points into
	 `substituted', and scan that.	We can't scan `substituted'
	 itself, since the tokenization process moves the buffer's
	 text pointer around, and we still need to be able to find
	 `substituted's original text buffer after scanning it so we
	 can free it.  */
      shared_macro_buffer substituted_src (substituted.text, substituted.len);
      scan (dest, &substituted_src, &new_no_loop, scope);

      return 1;
    }
  else
    internal_error (_("bad macro definition kind"));
}


/* If the single token in SRC_FIRST followed by the tokens in SRC_REST
   constitute a macro invocation not forbidden in NO_LOOP, append its
   expansion to DEST and return non-zero.  Otherwise, return zero, and
   leave DEST unchanged.

   SRC_FIRST must be a string built by get_token.  */
static int
maybe_expand (growable_macro_buffer *dest,
	      shared_macro_buffer *src_first,
	      shared_macro_buffer *src_rest,
	      struct macro_name_list *no_loop,
	      const macro_scope &scope)
{
  /* Is this token an identifier?  */
  if (src_first->is_identifier)
    {
      /* Make a null-terminated copy of it, since that's what our
	 lookup function expects.  */
      std::string id (src_first->text, src_first->len);

      /* If we're currently re-scanning the result of expanding
	 this macro, don't expand it again.  */
      if (! currently_rescanning (no_loop, id.c_str ()))
	{
	  /* Does this identifier have a macro definition in scope?  */
	  macro_definition *def = standard_macro_lookup (id.c_str (), scope);

	  if (def && expand (id.c_str (), def, dest, src_rest, no_loop, scope))
	    return 1;
	}
    }

  return 0;
}


/* Expand macro references in SRC, appending the results to DEST.
   Assume we are re-scanning the result of expanding the macros named
   in NO_LOOP, and don't try to re-expand references to them.  */

static void
scan (growable_macro_buffer *dest,
      shared_macro_buffer *src,
      struct macro_name_list *no_loop,
      const macro_scope &scope)
{

  for (;;)
    {
      shared_macro_buffer tok;
      const char *original_src_start = src->text;

      /* Find the next token in SRC.  */
      if (! get_token (&tok, src))
	break;

      /* Just for aesthetics.  If we skipped some whitespace, copy
	 that to DEST.  */
      if (tok.text > original_src_start)
	{
	  dest->appendmem (original_src_start, tok.text - original_src_start);
	  dest->last_token = dest->len;
	}

      if (! maybe_expand (dest, &tok, src, no_loop, scope))
	/* We didn't end up expanding tok as a macro reference, so
	   simply append it to dest.  */
	append_tokens_without_splicing (dest, &tok);
    }

  /* Just for aesthetics.  If there was any trailing whitespace in
     src, copy it to dest.  */
  if (src->len)
    {
      dest->appendmem (src->text, src->len);
      dest->last_token = dest->len;
    }
}


gdb::unique_xmalloc_ptr<char>
macro_expand (const char *source, const macro_scope &scope)
{
  shared_macro_buffer src (source, strlen (source));

  growable_macro_buffer dest (0);
  dest.last_token = 0;

  scan (&dest, &src, 0, scope);

  dest.appendc ('\0');

  return dest.release ();
}


gdb::unique_xmalloc_ptr<char>
macro_expand_once (const char *source, const macro_scope &scope)
{
  error (_("Expand-once not implemented yet."));
}

gdb::unique_xmalloc_ptr<char>
macro_expand_next (const char **lexptr, const macro_scope &scope)
{
  shared_macro_buffer tok;

  /* Set up SRC to refer to the input text, pointed to by *lexptr.  */
  shared_macro_buffer src (*lexptr, strlen (*lexptr));

  /* Set up DEST to receive the expansion, if there is one.  */
  growable_macro_buffer dest (0);
  dest.last_token = 0;

  /* Get the text's first preprocessing token.  */
  if (! get_token (&tok, &src))
    return nullptr;

  /* If it's a macro invocation, expand it.  */
  if (maybe_expand (&dest, &tok, &src, 0, scope))
    {
      /* It was a macro invocation!  Package up the expansion as a
	 null-terminated string and return it.  Set *lexptr to the
	 start of the next token in the input.  */
      dest.appendc ('\0');
      *lexptr = src.text;
      return dest.release ();
    }
  else
    {
      /* It wasn't a macro invocation.  */
      return nullptr;
    }
}