aboutsummaryrefslogtreecommitdiff
path: root/gdb/frame.c
blob: 6bfa31e630e44d9c3efcb1243fcb5b1db220d951 (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
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
/* Cache and manage frames for GDB, the GNU debugger.

   Copyright (C) 1986-2020 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 "frame.h"
#include "target.h"
#include "value.h"
#include "inferior.h"	/* for inferior_ptid */
#include "regcache.h"
#include "user-regs.h"
#include "gdb_obstack.h"
#include "dummy-frame.h"
#include "sentinel-frame.h"
#include "gdbcore.h"
#include "annotate.h"
#include "language.h"
#include "frame-unwind.h"
#include "frame-base.h"
#include "command.h"
#include "gdbcmd.h"
#include "observable.h"
#include "objfiles.h"
#include "gdbthread.h"
#include "block.h"
#include "inline-frame.h"
#include "tracepoint.h"
#include "hashtab.h"
#include "valprint.h"
#include "cli/cli-option.h"

/* The sentinel frame terminates the innermost end of the frame chain.
   If unwound, it returns the information needed to construct an
   innermost frame.

   The current frame, which is the innermost frame, can be found at
   sentinel_frame->prev.  */

static struct frame_info *sentinel_frame;

/* Number of calls to reinit_frame_cache.  */
static unsigned int frame_cache_generation = 0;

/* See frame.h.  */

unsigned int
get_frame_cache_generation ()
{
  return frame_cache_generation;
}

/* The values behind the global "set backtrace ..." settings.  */
set_backtrace_options user_set_backtrace_options;

static struct frame_info *get_prev_frame_raw (struct frame_info *this_frame);
static const char *frame_stop_reason_symbol_string (enum unwind_stop_reason reason);

/* Status of some values cached in the frame_info object.  */

enum cached_copy_status
{
  /* Value is unknown.  */
  CC_UNKNOWN,

  /* We have a value.  */
  CC_VALUE,

  /* Value was not saved.  */
  CC_NOT_SAVED,

  /* Value is unavailable.  */
  CC_UNAVAILABLE
};

enum class frame_id_status
{
  /* Frame id is not computed.  */
  NOT_COMPUTED = 0,

  /* Frame id is being computed (compute_frame_id is active).  */
  COMPUTING,

  /* Frame id has been computed.  */
  COMPUTED,
};

/* We keep a cache of stack frames, each of which is a "struct
   frame_info".  The innermost one gets allocated (in
   wait_for_inferior) each time the inferior stops; sentinel_frame
   points to it.  Additional frames get allocated (in get_prev_frame)
   as needed, and are chained through the next and prev fields.  Any
   time that the frame cache becomes invalid (most notably when we
   execute something, but also if we change how we interpret the
   frames (e.g. "set heuristic-fence-post" in mips-tdep.c, or anything
   which reads new symbols)), we should call reinit_frame_cache.  */

struct frame_info
{
  /* Level of this frame.  The inner-most (youngest) frame is at level
     0.  As you move towards the outer-most (oldest) frame, the level
     increases.  This is a cached value.  It could just as easily be
     computed by counting back from the selected frame to the inner
     most frame.  */
  /* NOTE: cagney/2002-04-05: Perhaps a level of ``-1'' should be
     reserved to indicate a bogus frame - one that has been created
     just to keep GDB happy (GDB always needs a frame).  For the
     moment leave this as speculation.  */
  int level;

  /* The frame's program space.  */
  struct program_space *pspace;

  /* The frame's address space.  */
  const address_space *aspace;

  /* The frame's low-level unwinder and corresponding cache.  The
     low-level unwinder is responsible for unwinding register values
     for the previous frame.  The low-level unwind methods are
     selected based on the presence, or otherwise, of register unwind
     information such as CFI.  */
  void *prologue_cache;
  const struct frame_unwind *unwind;

  /* Cached copy of the previous frame's architecture.  */
  struct
  {
    bool p;
    struct gdbarch *arch;
  } prev_arch;

  /* Cached copy of the previous frame's resume address.  */
  struct {
    cached_copy_status status;
    /* Did VALUE require unmasking when being read.  */
    bool masked;
    CORE_ADDR value;
  } prev_pc;

  /* Cached copy of the previous frame's function address.  */
  struct
  {
    CORE_ADDR addr;
    cached_copy_status status;
  } prev_func;

  /* This frame's ID.  */
  struct
  {
    frame_id_status p;
    struct frame_id value;
  } this_id;

  /* The frame's high-level base methods, and corresponding cache.
     The high level base methods are selected based on the frame's
     debug info.  */
  const struct frame_base *base;
  void *base_cache;

  /* Pointers to the next (down, inner, younger) and previous (up,
     outer, older) frame_info's in the frame cache.  */
  struct frame_info *next; /* down, inner, younger */
  bool prev_p;
  struct frame_info *prev; /* up, outer, older */

  /* The reason why we could not set PREV, or UNWIND_NO_REASON if we
     could.  Only valid when PREV_P is set.  */
  enum unwind_stop_reason stop_reason;

  /* A frame specific string describing the STOP_REASON in more detail.
     Only valid when PREV_P is set, but even then may still be NULL.  */
  const char *stop_string;
};

/* See frame.h.  */

void
set_frame_previous_pc_masked (struct frame_info *frame)
{
  frame->prev_pc.masked = true;
}

/* See frame.h.  */

bool
get_frame_pc_masked (const struct frame_info *frame)
{
  gdb_assert (frame->next != nullptr);
  gdb_assert (frame->next->prev_pc.status == CC_VALUE);

  return frame->next->prev_pc.masked;
}

/* A frame stash used to speed up frame lookups.  Create a hash table
   to stash frames previously accessed from the frame cache for
   quicker subsequent retrieval.  The hash table is emptied whenever
   the frame cache is invalidated.  */

static htab_t frame_stash;

/* Internal function to calculate a hash from the frame_id addresses,
   using as many valid addresses as possible.  Frames below level 0
   are not stored in the hash table.  */

static hashval_t
frame_addr_hash (const void *ap)
{
  const struct frame_info *frame = (const struct frame_info *) ap;
  const struct frame_id f_id = frame->this_id.value;
  hashval_t hash = 0;

  gdb_assert (f_id.stack_status != FID_STACK_INVALID
	      || f_id.code_addr_p
	      || f_id.special_addr_p);

  if (f_id.stack_status == FID_STACK_VALID)
    hash = iterative_hash (&f_id.stack_addr,
			   sizeof (f_id.stack_addr), hash);
  if (f_id.code_addr_p)
    hash = iterative_hash (&f_id.code_addr,
			   sizeof (f_id.code_addr), hash);
  if (f_id.special_addr_p)
    hash = iterative_hash (&f_id.special_addr,
			   sizeof (f_id.special_addr), hash);

  return hash;
}

/* Internal equality function for the hash table.  This function
   defers equality operations to frame_id_eq.  */

static int
frame_addr_hash_eq (const void *a, const void *b)
{
  const struct frame_info *f_entry = (const struct frame_info *) a;
  const struct frame_info *f_element = (const struct frame_info *) b;

  return frame_id_eq (f_entry->this_id.value,
		      f_element->this_id.value);
}

/* Internal function to create the frame_stash hash table.  100 seems
   to be a good compromise to start the hash table at.  */

static void
frame_stash_create (void)
{
  frame_stash = htab_create (100,
			     frame_addr_hash,
			     frame_addr_hash_eq,
			     NULL);
}

/* Internal function to add a frame to the frame_stash hash table.
   Returns false if a frame with the same ID was already stashed, true
   otherwise.  */

static bool
frame_stash_add (frame_info *frame)
{
  /* Do not try to stash the sentinel frame.  */
  gdb_assert (frame->level >= 0);

  frame_info **slot = (struct frame_info **) htab_find_slot (frame_stash,
							     frame, INSERT);

  /* If we already have a frame in the stack with the same id, we
     either have a stack cycle (corrupted stack?), or some bug
     elsewhere in GDB.  In any case, ignore the duplicate and return
     an indication to the caller.  */
  if (*slot != nullptr)
    return false;

  *slot = frame;
  return true;
}

/* Internal function to search the frame stash for an entry with the
   given frame ID.  If found, return that frame.  Otherwise return
   NULL.  */

static struct frame_info *
frame_stash_find (struct frame_id id)
{
  struct frame_info dummy;
  struct frame_info *frame;

  dummy.this_id.value = id;
  frame = (struct frame_info *) htab_find (frame_stash, &dummy);
  return frame;
}

/* Internal function to invalidate the frame stash by removing all
   entries in it.  This only occurs when the frame cache is
   invalidated.  */

static void
frame_stash_invalidate (void)
{
  htab_empty (frame_stash);
}

/* See frame.h  */
scoped_restore_selected_frame::scoped_restore_selected_frame ()
{
  m_fid = get_frame_id (get_selected_frame (NULL));
}

/* See frame.h  */
scoped_restore_selected_frame::~scoped_restore_selected_frame ()
{
  frame_info *frame = frame_find_by_id (m_fid);
  if (frame == NULL)
    warning (_("Unable to restore previously selected frame."));
  else
    select_frame (frame);
}

/* Flag to control debugging.  */

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

/* Implementation of "show backtrace past-main".  */

static void
show_backtrace_past_main (struct ui_file *file, int from_tty,
			  struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file,
		    _("Whether backtraces should "
		      "continue past \"main\" is %s.\n"),
		    value);
}

/* Implementation of "show backtrace past-entry".  */

static void
show_backtrace_past_entry (struct ui_file *file, int from_tty,
			   struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Whether backtraces should continue past the "
			    "entry point of a program is %s.\n"),
		    value);
}

/* Implementation of "show backtrace limit".  */

static void
show_backtrace_limit (struct ui_file *file, int from_tty,
		      struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file,
		    _("An upper bound on the number "
		      "of backtrace levels is %s.\n"),
		    value);
}


static void
fprint_field (struct ui_file *file, const char *name, int p, CORE_ADDR addr)
{
  if (p)
    fprintf_unfiltered (file, "%s=%s", name, hex_string (addr));
  else
    fprintf_unfiltered (file, "!%s", name);
}

void
fprint_frame_id (struct ui_file *file, struct frame_id id)
{
  fprintf_unfiltered (file, "{");

  if (id.stack_status == FID_STACK_INVALID)
    fprintf_unfiltered (file, "!stack");
  else if (id.stack_status == FID_STACK_UNAVAILABLE)
    fprintf_unfiltered (file, "stack=<unavailable>");
  else if (id.stack_status == FID_STACK_SENTINEL)
    fprintf_unfiltered (file, "stack=<sentinel>");
  else if (id.stack_status == FID_STACK_OUTER)
    fprintf_unfiltered (file, "stack=<outer>");
  else
    fprintf_unfiltered (file, "stack=%s", hex_string (id.stack_addr));

  fprintf_unfiltered (file, ",");

  fprint_field (file, "code", id.code_addr_p, id.code_addr);
  fprintf_unfiltered (file, ",");

  fprint_field (file, "special", id.special_addr_p, id.special_addr);

  if (id.artificial_depth)
    fprintf_unfiltered (file, ",artificial=%d", id.artificial_depth);

  fprintf_unfiltered (file, "}");
}

static void
fprint_frame_type (struct ui_file *file, enum frame_type type)
{
  switch (type)
    {
    case NORMAL_FRAME:
      fprintf_unfiltered (file, "NORMAL_FRAME");
      return;
    case DUMMY_FRAME:
      fprintf_unfiltered (file, "DUMMY_FRAME");
      return;
    case INLINE_FRAME:
      fprintf_unfiltered (file, "INLINE_FRAME");
      return;
    case TAILCALL_FRAME:
      fprintf_unfiltered (file, "TAILCALL_FRAME");
      return;
    case SIGTRAMP_FRAME:
      fprintf_unfiltered (file, "SIGTRAMP_FRAME");
      return;
    case ARCH_FRAME:
      fprintf_unfiltered (file, "ARCH_FRAME");
      return;
    case SENTINEL_FRAME:
      fprintf_unfiltered (file, "SENTINEL_FRAME");
      return;
    default:
      fprintf_unfiltered (file, "<unknown type>");
      return;
    };
}

static void
fprint_frame (struct ui_file *file, struct frame_info *fi)
{
  if (fi == NULL)
    {
      fprintf_unfiltered (file, "<NULL frame>");
      return;
    }

  fprintf_unfiltered (file, "{");
  fprintf_unfiltered (file, "level=%d", fi->level);
  fprintf_unfiltered (file, ",");

  fprintf_unfiltered (file, "type=");
  if (fi->unwind != NULL)
    fprint_frame_type (file, fi->unwind->type);
  else
    fprintf_unfiltered (file, "<unknown>");
  fprintf_unfiltered (file, ",");

  fprintf_unfiltered (file, "unwind=");
  if (fi->unwind != NULL)
    gdb_print_host_address (fi->unwind, file);
  else
    fprintf_unfiltered (file, "<unknown>");
  fprintf_unfiltered (file, ",");

  fprintf_unfiltered (file, "pc=");
  if (fi->next == NULL || fi->next->prev_pc.status == CC_UNKNOWN)
    fprintf_unfiltered (file, "<unknown>");
  else if (fi->next->prev_pc.status == CC_VALUE)
    {
      fprintf_unfiltered (file, "%s", hex_string (fi->next->prev_pc.value));
      if (fi->next->prev_pc.masked)
	fprintf_unfiltered (file, "[PAC]");
    }
  else if (fi->next->prev_pc.status == CC_NOT_SAVED)
    val_print_not_saved (file);
  else if (fi->next->prev_pc.status == CC_UNAVAILABLE)
    val_print_unavailable (file);
  fprintf_unfiltered (file, ",");

  fprintf_unfiltered (file, "id=");
  if (fi->this_id.p == frame_id_status::NOT_COMPUTED)
    fprintf_unfiltered (file, "<not computed>");
  else if (fi->this_id.p == frame_id_status::COMPUTING)
    fprintf_unfiltered (file, "<computing>");
  else
    fprint_frame_id (file, fi->this_id.value);
  fprintf_unfiltered (file, ",");

  fprintf_unfiltered (file, "func=");
  if (fi->next != NULL && fi->next->prev_func.status == CC_VALUE)
    fprintf_unfiltered (file, "%s", hex_string (fi->next->prev_func.addr));
  else
    fprintf_unfiltered (file, "<unknown>");
  fprintf_unfiltered (file, "}");
}

/* Given FRAME, return the enclosing frame as found in real frames read-in from
   inferior memory.  Skip any previous frames which were made up by GDB.
   Return FRAME if FRAME is a non-artificial frame.
   Return NULL if FRAME is the start of an artificial-only chain.  */

static struct frame_info *
skip_artificial_frames (struct frame_info *frame)
{
  /* Note we use get_prev_frame_always, and not get_prev_frame.  The
     latter will truncate the frame chain, leading to this function
     unintentionally returning a null_frame_id (e.g., when the user
     sets a backtrace limit).

     Note that for record targets we may get a frame chain that consists
     of artificial frames only.  */
  while (get_frame_type (frame) == INLINE_FRAME
	 || get_frame_type (frame) == TAILCALL_FRAME)
    {
      frame = get_prev_frame_always (frame);
      if (frame == NULL)
	break;
    }

  return frame;
}

struct frame_info *
skip_unwritable_frames (struct frame_info *frame)
{
  while (gdbarch_code_of_frame_writable (get_frame_arch (frame), frame) == 0)
    {
      frame = get_prev_frame (frame);
      if (frame == NULL)
	break;
    }

  return frame;
}

/* See frame.h.  */

struct frame_info *
skip_tailcall_frames (struct frame_info *frame)
{
  while (get_frame_type (frame) == TAILCALL_FRAME)
    {
      /* Note that for record targets we may get a frame chain that consists of
	 tailcall frames only.  */
      frame = get_prev_frame (frame);
      if (frame == NULL)
	break;
    }

  return frame;
}

/* Compute the frame's uniq ID that can be used to, later, re-find the
   frame.  */

static void
compute_frame_id (struct frame_info *fi)
{
  gdb_assert (fi->this_id.p == frame_id_status::NOT_COMPUTED);

  unsigned int entry_generation = get_frame_cache_generation ();

  try
    {
      /* Mark this frame's id as "being computed.  */
      fi->this_id.p = frame_id_status::COMPUTING;

      if (frame_debug)
	fprintf_unfiltered (gdb_stdlog, "{ compute_frame_id (fi=%d) ",
			    fi->level);

      /* Find the unwinder.  */
      if (fi->unwind == NULL)
	frame_unwind_find_by_frame (fi, &fi->prologue_cache);

      /* Find THIS frame's ID.  */
      /* Default to outermost if no ID is found.  */
      fi->this_id.value = outer_frame_id;
      fi->unwind->this_id (fi, &fi->prologue_cache, &fi->this_id.value);
      gdb_assert (frame_id_p (fi->this_id.value));

      /* Mark this frame's id as "computed".  */
      fi->this_id.p = frame_id_status::COMPUTED;

      if (frame_debug)
	{
	  fprintf_unfiltered (gdb_stdlog, "-> ");
	  fprint_frame_id (gdb_stdlog, fi->this_id.value);
	  fprintf_unfiltered (gdb_stdlog, " }\n");
	}
    }
  catch (const gdb_exception &ex)
    {
      /* On error, revert the frame id status to not computed.  If the frame
         cache generation changed, the frame object doesn't exist anymore, so
	 don't touch it.  */
      if (get_frame_cache_generation () == entry_generation)
	fi->this_id.p = frame_id_status::NOT_COMPUTED;

      throw;
    }
}

/* Return a frame uniq ID that can be used to, later, re-find the
   frame.  */

struct frame_id
get_frame_id (struct frame_info *fi)
{
  if (fi == NULL)
    return null_frame_id;

  /* It's always invalid to try to get a frame's id while it is being
     computed.  */
  gdb_assert (fi->this_id.p != frame_id_status::COMPUTING);

  if (fi->this_id.p == frame_id_status::NOT_COMPUTED)
    {
      /* If we haven't computed the frame id yet, then it must be that
	 this is the current frame.  Compute it now, and stash the
	 result.  The IDs of other frames are computed as soon as
	 they're created, in order to detect cycles.  See
	 get_prev_frame_if_no_cycle.  */
      gdb_assert (fi->level == 0);

      /* Compute.  */
      compute_frame_id (fi);

      /* Since this is the first frame in the chain, this should
	 always succeed.  */
      bool stashed = frame_stash_add (fi);
      gdb_assert (stashed);
    }

  return fi->this_id.value;
}

struct frame_id
get_stack_frame_id (struct frame_info *next_frame)
{
  return get_frame_id (skip_artificial_frames (next_frame));
}

struct frame_id
frame_unwind_caller_id (struct frame_info *next_frame)
{
  struct frame_info *this_frame;

  /* Use get_prev_frame_always, and not get_prev_frame.  The latter
     will truncate the frame chain, leading to this function
     unintentionally returning a null_frame_id (e.g., when a caller
     requests the frame ID of "main()"s caller.  */

  next_frame = skip_artificial_frames (next_frame);
  if (next_frame == NULL)
    return null_frame_id;

  this_frame = get_prev_frame_always (next_frame);
  if (this_frame)
    return get_frame_id (skip_artificial_frames (this_frame));
  else
    return null_frame_id;
}

const struct frame_id null_frame_id = { 0 }; /* All zeros.  */
const struct frame_id sentinel_frame_id = { 0, 0, 0, FID_STACK_SENTINEL, 0, 1, 0 };
const struct frame_id outer_frame_id = { 0, 0, 0, FID_STACK_OUTER, 0, 1, 0 };

struct frame_id
frame_id_build_special (CORE_ADDR stack_addr, CORE_ADDR code_addr,
                        CORE_ADDR special_addr)
{
  struct frame_id id = null_frame_id;

  id.stack_addr = stack_addr;
  id.stack_status = FID_STACK_VALID;
  id.code_addr = code_addr;
  id.code_addr_p = true;
  id.special_addr = special_addr;
  id.special_addr_p = true;
  return id;
}

/* See frame.h.  */

struct frame_id
frame_id_build_unavailable_stack (CORE_ADDR code_addr)
{
  struct frame_id id = null_frame_id;

  id.stack_status = FID_STACK_UNAVAILABLE;
  id.code_addr = code_addr;
  id.code_addr_p = true;
  return id;
}

/* See frame.h.  */

struct frame_id
frame_id_build_unavailable_stack_special (CORE_ADDR code_addr,
					  CORE_ADDR special_addr)
{
  struct frame_id id = null_frame_id;

  id.stack_status = FID_STACK_UNAVAILABLE;
  id.code_addr = code_addr;
  id.code_addr_p = true;
  id.special_addr = special_addr;
  id.special_addr_p = true;
  return id;
}

struct frame_id
frame_id_build (CORE_ADDR stack_addr, CORE_ADDR code_addr)
{
  struct frame_id id = null_frame_id;

  id.stack_addr = stack_addr;
  id.stack_status = FID_STACK_VALID;
  id.code_addr = code_addr;
  id.code_addr_p = true;
  return id;
}

struct frame_id
frame_id_build_wild (CORE_ADDR stack_addr)
{
  struct frame_id id = null_frame_id;

  id.stack_addr = stack_addr;
  id.stack_status = FID_STACK_VALID;
  return id;
}

bool
frame_id_p (frame_id l)
{
  /* The frame is valid iff it has a valid stack address.  */
  bool p = l.stack_status != FID_STACK_INVALID;

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "{ frame_id_p (l=");
      fprint_frame_id (gdb_stdlog, l);
      fprintf_unfiltered (gdb_stdlog, ") -> %d }\n", p);
    }

  return p;
}

bool
frame_id_artificial_p (frame_id l)
{
  if (!frame_id_p (l))
    return false;

  return l.artificial_depth != 0;
}

bool
frame_id_eq (frame_id l, frame_id r)
{
  bool eq;

  if (l.stack_status == FID_STACK_INVALID
      || r.stack_status == FID_STACK_INVALID)
    /* Like a NaN, if either ID is invalid, the result is false.
       Note that a frame ID is invalid iff it is the null frame ID.  */
    eq = false;
  else if (l.stack_status != r.stack_status || l.stack_addr != r.stack_addr)
    /* If .stack addresses are different, the frames are different.  */
    eq = false;
  else if (l.code_addr_p && r.code_addr_p && l.code_addr != r.code_addr)
    /* An invalid code addr is a wild card.  If .code addresses are
       different, the frames are different.  */
    eq = false;
  else if (l.special_addr_p && r.special_addr_p
	   && l.special_addr != r.special_addr)
    /* An invalid special addr is a wild card (or unused).  Otherwise
       if special addresses are different, the frames are different.  */
    eq = false;
  else if (l.artificial_depth != r.artificial_depth)
    /* If artificial depths are different, the frames must be different.  */
    eq = false;
  else
    /* Frames are equal.  */
    eq = true;

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "{ frame_id_eq (l=");
      fprint_frame_id (gdb_stdlog, l);
      fprintf_unfiltered (gdb_stdlog, ",r=");
      fprint_frame_id (gdb_stdlog, r);
      fprintf_unfiltered (gdb_stdlog, ") -> %d }\n", eq);
    }

  return eq;
}

/* Safety net to check whether frame ID L should be inner to
   frame ID R, according to their stack addresses.

   This method cannot be used to compare arbitrary frames, as the
   ranges of valid stack addresses may be discontiguous (e.g. due
   to sigaltstack).

   However, it can be used as safety net to discover invalid frame
   IDs in certain circumstances.  Assuming that NEXT is the immediate
   inner frame to THIS and that NEXT and THIS are both NORMAL frames:

   * The stack address of NEXT must be inner-than-or-equal to the stack
     address of THIS.

     Therefore, if frame_id_inner (THIS, NEXT) holds, some unwind
     error has occurred.

   * If NEXT and THIS have different stack addresses, no other frame
     in the frame chain may have a stack address in between.

     Therefore, if frame_id_inner (TEST, THIS) holds, but
     frame_id_inner (TEST, NEXT) does not hold, TEST cannot refer
     to a valid frame in the frame chain.

   The sanity checks above cannot be performed when a SIGTRAMP frame
   is involved, because signal handlers might be executed on a different
   stack than the stack used by the routine that caused the signal
   to be raised.  This can happen for instance when a thread exceeds
   its maximum stack size.  In this case, certain compilers implement
   a stack overflow strategy that cause the handler to be run on a
   different stack.  */

static bool
frame_id_inner (struct gdbarch *gdbarch, struct frame_id l, struct frame_id r)
{
  bool inner;

  if (l.stack_status != FID_STACK_VALID || r.stack_status != FID_STACK_VALID)
    /* Like NaN, any operation involving an invalid ID always fails.
       Likewise if either ID has an unavailable stack address.  */
    inner = false;
  else if (l.artificial_depth > r.artificial_depth
	   && l.stack_addr == r.stack_addr
	   && l.code_addr_p == r.code_addr_p
	   && l.special_addr_p == r.special_addr_p
	   && l.special_addr == r.special_addr)
    {
      /* Same function, different inlined functions.  */
      const struct block *lb, *rb;

      gdb_assert (l.code_addr_p && r.code_addr_p);

      lb = block_for_pc (l.code_addr);
      rb = block_for_pc (r.code_addr);

      if (lb == NULL || rb == NULL)
	/* Something's gone wrong.  */
	inner = false;
      else
	/* This will return true if LB and RB are the same block, or
	   if the block with the smaller depth lexically encloses the
	   block with the greater depth.  */
	inner = contained_in (lb, rb);
    }
  else
    /* Only return non-zero when strictly inner than.  Note that, per
       comment in "frame.h", there is some fuzz here.  Frameless
       functions are not strictly inner than (same .stack but
       different .code and/or .special address).  */
    inner = gdbarch_inner_than (gdbarch, l.stack_addr, r.stack_addr);

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "{ frame_id_inner (l=");
      fprint_frame_id (gdb_stdlog, l);
      fprintf_unfiltered (gdb_stdlog, ",r=");
      fprint_frame_id (gdb_stdlog, r);
      fprintf_unfiltered (gdb_stdlog, ") -> %d }\n", inner);
    }

  return inner;
}

struct frame_info *
frame_find_by_id (struct frame_id id)
{
  struct frame_info *frame, *prev_frame;

  /* ZERO denotes the null frame, let the caller decide what to do
     about it.  Should it instead return get_current_frame()?  */
  if (!frame_id_p (id))
    return NULL;

  /* Check for the sentinel frame.  */
  if (frame_id_eq (id, sentinel_frame_id))
    return sentinel_frame;

  /* Try using the frame stash first.  Finding it there removes the need
     to perform the search by looping over all frames, which can be very
     CPU-intensive if the number of frames is very high (the loop is O(n)
     and get_prev_frame performs a series of checks that are relatively
     expensive).  This optimization is particularly useful when this function
     is called from another function (such as value_fetch_lazy, case
     VALUE_LVAL (val) == lval_register) which already loops over all frames,
     making the overall behavior O(n^2).  */
  frame = frame_stash_find (id);
  if (frame)
    return frame;

  for (frame = get_current_frame (); ; frame = prev_frame)
    {
      struct frame_id self = get_frame_id (frame);

      if (frame_id_eq (id, self))
	/* An exact match.  */
	return frame;

      prev_frame = get_prev_frame (frame);
      if (!prev_frame)
	return NULL;

      /* As a safety net to avoid unnecessary backtracing while trying
	 to find an invalid ID, we check for a common situation where
	 we can detect from comparing stack addresses that no other
	 frame in the current frame chain can have this ID.  See the
	 comment at frame_id_inner for details.   */
      if (get_frame_type (frame) == NORMAL_FRAME
	  && !frame_id_inner (get_frame_arch (frame), id, self)
	  && frame_id_inner (get_frame_arch (prev_frame), id,
			     get_frame_id (prev_frame)))
	return NULL;
    }
  return NULL;
}

static CORE_ADDR
frame_unwind_pc (struct frame_info *this_frame)
{
  if (this_frame->prev_pc.status == CC_UNKNOWN)
    {
      struct gdbarch *prev_gdbarch;
      CORE_ADDR pc = 0;
      bool pc_p = false;

      /* The right way.  The `pure' way.  The one true way.  This
	 method depends solely on the register-unwind code to
	 determine the value of registers in THIS frame, and hence
	 the value of this frame's PC (resume address).  A typical
	 implementation is no more than:

	 frame_unwind_register (this_frame, ISA_PC_REGNUM, buf);
	 return extract_unsigned_integer (buf, size of ISA_PC_REGNUM);

	 Note: this method is very heavily dependent on a correct
	 register-unwind implementation, it pays to fix that
	 method first; this method is frame type agnostic, since
	 it only deals with register values, it works with any
	 frame.  This is all in stark contrast to the old
	 FRAME_SAVED_PC which would try to directly handle all the
	 different ways that a PC could be unwound.  */
      prev_gdbarch = frame_unwind_arch (this_frame);

      try
	{
	  pc = gdbarch_unwind_pc (prev_gdbarch, this_frame);
	  pc_p = true;
	}
      catch (const gdb_exception_error &ex)
	{
	  if (ex.error == NOT_AVAILABLE_ERROR)
	    {
	      this_frame->prev_pc.status = CC_UNAVAILABLE;

	      if (frame_debug)
		fprintf_unfiltered (gdb_stdlog,
				    "{ frame_unwind_pc (this_frame=%d)"
				    " -> <unavailable> }\n",
				    this_frame->level);
	    }
	  else if (ex.error == OPTIMIZED_OUT_ERROR)
	    {
	      this_frame->prev_pc.status = CC_NOT_SAVED;

	      if (frame_debug)
		fprintf_unfiltered (gdb_stdlog,
				    "{ frame_unwind_pc (this_frame=%d)"
				    " -> <not saved> }\n",
				    this_frame->level);
	    }
	  else
	    throw;
	}

      if (pc_p)
	{
	  this_frame->prev_pc.value = pc;
	  this_frame->prev_pc.status = CC_VALUE;
	  if (frame_debug)
	    fprintf_unfiltered (gdb_stdlog,
				"{ frame_unwind_pc (this_frame=%d) "
				"-> %s }\n",
				this_frame->level,
				hex_string (this_frame->prev_pc.value));
	}
    }

  if (this_frame->prev_pc.status == CC_VALUE)
    return this_frame->prev_pc.value;
  else if (this_frame->prev_pc.status == CC_UNAVAILABLE)
    throw_error (NOT_AVAILABLE_ERROR, _("PC not available"));
  else if (this_frame->prev_pc.status == CC_NOT_SAVED)
    throw_error (OPTIMIZED_OUT_ERROR, _("PC not saved"));
  else
    internal_error (__FILE__, __LINE__,
		    "unexpected prev_pc status: %d",
		    (int) this_frame->prev_pc.status);
}

CORE_ADDR
frame_unwind_caller_pc (struct frame_info *this_frame)
{
  this_frame = skip_artificial_frames (this_frame);

  /* We must have a non-artificial frame.  The caller is supposed to check
     the result of frame_unwind_caller_id (), which returns NULL_FRAME_ID
     in this case.  */
  gdb_assert (this_frame != NULL);

  return frame_unwind_pc (this_frame);
}

bool
get_frame_func_if_available (frame_info *this_frame, CORE_ADDR *pc)
{
  struct frame_info *next_frame = this_frame->next;

  if (next_frame->prev_func.status == CC_UNKNOWN)
    {
      CORE_ADDR addr_in_block;

      /* Make certain that this, and not the adjacent, function is
         found.  */
      if (!get_frame_address_in_block_if_available (this_frame, &addr_in_block))
	{
	  next_frame->prev_func.status = CC_UNAVAILABLE;
	  if (frame_debug)
	    fprintf_unfiltered (gdb_stdlog,
				"{ get_frame_func (this_frame=%d)"
				" -> unavailable }\n",
				this_frame->level);
	}
      else
	{
	  next_frame->prev_func.status = CC_VALUE;
	  next_frame->prev_func.addr = get_pc_function_start (addr_in_block);
	  if (frame_debug)
	    fprintf_unfiltered (gdb_stdlog,
				"{ get_frame_func (this_frame=%d) -> %s }\n",
				this_frame->level,
				hex_string (next_frame->prev_func.addr));
	}
    }

  if (next_frame->prev_func.status == CC_UNAVAILABLE)
    {
      *pc = -1;
      return false;
    }
  else
    {
      gdb_assert (next_frame->prev_func.status == CC_VALUE);

      *pc = next_frame->prev_func.addr;
      return true;
    }
}

CORE_ADDR
get_frame_func (struct frame_info *this_frame)
{
  CORE_ADDR pc;

  if (!get_frame_func_if_available (this_frame, &pc))
    throw_error (NOT_AVAILABLE_ERROR, _("PC not available"));

  return pc;
}

std::unique_ptr<readonly_detached_regcache>
frame_save_as_regcache (struct frame_info *this_frame)
{
  auto cooked_read = [this_frame] (int regnum, gdb_byte *buf)
    {
      if (!deprecated_frame_register_read (this_frame, regnum, buf))
	return REG_UNAVAILABLE;
      else
	return REG_VALID;
    };

  std::unique_ptr<readonly_detached_regcache> regcache
    (new readonly_detached_regcache (get_frame_arch (this_frame), cooked_read));

  return regcache;
}

void
frame_pop (struct frame_info *this_frame)
{
  struct frame_info *prev_frame;

  if (get_frame_type (this_frame) == DUMMY_FRAME)
    {
      /* Popping a dummy frame involves restoring more than just registers.
	 dummy_frame_pop does all the work.  */
      dummy_frame_pop (get_frame_id (this_frame), inferior_thread ());
      return;
    }

  /* Ensure that we have a frame to pop to.  */
  prev_frame = get_prev_frame_always (this_frame);

  if (!prev_frame)
    error (_("Cannot pop the initial frame."));

  /* Ignore TAILCALL_FRAME type frames, they were executed already before
     entering THISFRAME.  */
  prev_frame = skip_tailcall_frames (prev_frame);

  if (prev_frame == NULL)
    error (_("Cannot find the caller frame."));

  /* Make a copy of all the register values unwound from this frame.
     Save them in a scratch buffer so that there isn't a race between
     trying to extract the old values from the current regcache while
     at the same time writing new values into that same cache.  */
  std::unique_ptr<readonly_detached_regcache> scratch
    = frame_save_as_regcache (prev_frame);

  /* FIXME: cagney/2003-03-16: It should be possible to tell the
     target's register cache that it is about to be hit with a burst
     register transfer and that the sequence of register writes should
     be batched.  The pair target_prepare_to_store() and
     target_store_registers() kind of suggest this functionality.
     Unfortunately, they don't implement it.  Their lack of a formal
     definition can lead to targets writing back bogus values
     (arguably a bug in the target code mind).  */
  /* Now copy those saved registers into the current regcache.  */
  get_current_regcache ()->restore (scratch.get ());

  /* We've made right mess of GDB's local state, just discard
     everything.  */
  reinit_frame_cache ();
}

void
frame_register_unwind (frame_info *next_frame, int regnum,
		       int *optimizedp, int *unavailablep,
		       enum lval_type *lvalp, CORE_ADDR *addrp,
		       int *realnump, gdb_byte *bufferp)
{
  struct value *value;

  /* Require all but BUFFERP to be valid.  A NULL BUFFERP indicates
     that the value proper does not need to be fetched.  */
  gdb_assert (optimizedp != NULL);
  gdb_assert (lvalp != NULL);
  gdb_assert (addrp != NULL);
  gdb_assert (realnump != NULL);
  /* gdb_assert (bufferp != NULL); */

  value = frame_unwind_register_value (next_frame, regnum);

  gdb_assert (value != NULL);

  *optimizedp = value_optimized_out (value);
  *unavailablep = !value_entirely_available (value);
  *lvalp = VALUE_LVAL (value);
  *addrp = value_address (value);
  if (*lvalp == lval_register)
    *realnump = VALUE_REGNUM (value);
  else
    *realnump = -1;

  if (bufferp)
    {
      if (!*optimizedp && !*unavailablep)
	memcpy (bufferp, value_contents_all (value),
		TYPE_LENGTH (value_type (value)));
      else
	memset (bufferp, 0, TYPE_LENGTH (value_type (value)));
    }

  /* Dispose of the new value.  This prevents watchpoints from
     trying to watch the saved frame pointer.  */
  release_value (value);
}

void
frame_register (struct frame_info *frame, int regnum,
		int *optimizedp, int *unavailablep, enum lval_type *lvalp,
		CORE_ADDR *addrp, int *realnump, gdb_byte *bufferp)
{
  /* Require all but BUFFERP to be valid.  A NULL BUFFERP indicates
     that the value proper does not need to be fetched.  */
  gdb_assert (optimizedp != NULL);
  gdb_assert (lvalp != NULL);
  gdb_assert (addrp != NULL);
  gdb_assert (realnump != NULL);
  /* gdb_assert (bufferp != NULL); */

  /* Obtain the register value by unwinding the register from the next
     (more inner frame).  */
  gdb_assert (frame != NULL && frame->next != NULL);
  frame_register_unwind (frame->next, regnum, optimizedp, unavailablep,
			 lvalp, addrp, realnump, bufferp);
}

void
frame_unwind_register (frame_info *next_frame, int regnum, gdb_byte *buf)
{
  int optimized;
  int unavailable;
  CORE_ADDR addr;
  int realnum;
  enum lval_type lval;

  frame_register_unwind (next_frame, regnum, &optimized, &unavailable,
			 &lval, &addr, &realnum, buf);

  if (optimized)
    throw_error (OPTIMIZED_OUT_ERROR,
		 _("Register %d was not saved"), regnum);
  if (unavailable)
    throw_error (NOT_AVAILABLE_ERROR,
		 _("Register %d is not available"), regnum);
}

void
get_frame_register (struct frame_info *frame,
		    int regnum, gdb_byte *buf)
{
  frame_unwind_register (frame->next, regnum, buf);
}

struct value *
frame_unwind_register_value (frame_info *next_frame, int regnum)
{
  struct gdbarch *gdbarch;
  struct value *value;

  gdb_assert (next_frame != NULL);
  gdbarch = frame_unwind_arch (next_frame);

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog,
			  "{ frame_unwind_register_value "
			  "(frame=%d,regnum=%d(%s),...) ",
			  next_frame->level, regnum,
			  user_reg_map_regnum_to_name (gdbarch, regnum));
    }

  /* Find the unwinder.  */
  if (next_frame->unwind == NULL)
    frame_unwind_find_by_frame (next_frame, &next_frame->prologue_cache);

  /* Ask this frame to unwind its register.  */
  value = next_frame->unwind->prev_register (next_frame,
					     &next_frame->prologue_cache,
					     regnum);

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "->");
      if (value_optimized_out (value))
	{
	  fprintf_unfiltered (gdb_stdlog, " ");
	  val_print_not_saved (gdb_stdlog);
	}
      else
	{
	  if (VALUE_LVAL (value) == lval_register)
	    fprintf_unfiltered (gdb_stdlog, " register=%d",
				VALUE_REGNUM (value));
	  else if (VALUE_LVAL (value) == lval_memory)
	    fprintf_unfiltered (gdb_stdlog, " address=%s",
				paddress (gdbarch,
					  value_address (value)));
	  else
	    fprintf_unfiltered (gdb_stdlog, " computed");

	  if (value_lazy (value))
	    fprintf_unfiltered (gdb_stdlog, " lazy");
	  else
	    {
	      int i;
	      const gdb_byte *buf = value_contents (value);

	      fprintf_unfiltered (gdb_stdlog, " bytes=");
	      fprintf_unfiltered (gdb_stdlog, "[");
	      for (i = 0; i < register_size (gdbarch, regnum); i++)
		fprintf_unfiltered (gdb_stdlog, "%02x", buf[i]);
	      fprintf_unfiltered (gdb_stdlog, "]");
	    }
	}

      fprintf_unfiltered (gdb_stdlog, " }\n");
    }

  return value;
}

struct value *
get_frame_register_value (struct frame_info *frame, int regnum)
{
  return frame_unwind_register_value (frame->next, regnum);
}

LONGEST
frame_unwind_register_signed (frame_info *next_frame, int regnum)
{
  struct gdbarch *gdbarch = frame_unwind_arch (next_frame);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  int size = register_size (gdbarch, regnum);
  struct value *value = frame_unwind_register_value (next_frame, regnum);

  gdb_assert (value != NULL);

  if (value_optimized_out (value))
    {
      throw_error (OPTIMIZED_OUT_ERROR,
		   _("Register %d was not saved"), regnum);
    }
  if (!value_entirely_available (value))
    {
      throw_error (NOT_AVAILABLE_ERROR,
		   _("Register %d is not available"), regnum);
    }

  LONGEST r = extract_signed_integer (value_contents_all (value), size,
				      byte_order);

  release_value (value);
  return r;
}

LONGEST
get_frame_register_signed (struct frame_info *frame, int regnum)
{
  return frame_unwind_register_signed (frame->next, regnum);
}

ULONGEST
frame_unwind_register_unsigned (frame_info *next_frame, int regnum)
{
  struct gdbarch *gdbarch = frame_unwind_arch (next_frame);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  int size = register_size (gdbarch, regnum);
  struct value *value = frame_unwind_register_value (next_frame, regnum);

  gdb_assert (value != NULL);

  if (value_optimized_out (value))
    {
      throw_error (OPTIMIZED_OUT_ERROR,
		   _("Register %d was not saved"), regnum);
    }
  if (!value_entirely_available (value))
    {
      throw_error (NOT_AVAILABLE_ERROR,
		   _("Register %d is not available"), regnum);
    }

  ULONGEST r = extract_unsigned_integer (value_contents_all (value), size,
					 byte_order);

  release_value (value);
  return r;
}

ULONGEST
get_frame_register_unsigned (struct frame_info *frame, int regnum)
{
  return frame_unwind_register_unsigned (frame->next, regnum);
}

bool
read_frame_register_unsigned (frame_info *frame, int regnum,
			      ULONGEST *val)
{
  struct value *regval = get_frame_register_value (frame, regnum);

  if (!value_optimized_out (regval)
      && value_entirely_available (regval))
    {
      struct gdbarch *gdbarch = get_frame_arch (frame);
      enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
      int size = register_size (gdbarch, VALUE_REGNUM (regval));

      *val = extract_unsigned_integer (value_contents (regval), size, byte_order);
      return true;
    }

  return false;
}

void
put_frame_register (struct frame_info *frame, int regnum,
		    const gdb_byte *buf)
{
  struct gdbarch *gdbarch = get_frame_arch (frame);
  int realnum;
  int optim;
  int unavail;
  enum lval_type lval;
  CORE_ADDR addr;

  frame_register (frame, regnum, &optim, &unavail,
		  &lval, &addr, &realnum, NULL);
  if (optim)
    error (_("Attempt to assign to a register that was not saved."));
  switch (lval)
    {
    case lval_memory:
      {
	write_memory (addr, buf, register_size (gdbarch, regnum));
	break;
      }
    case lval_register:
      get_current_regcache ()->cooked_write (realnum, buf);
      break;
    default:
      error (_("Attempt to assign to an unmodifiable value."));
    }
}

/* This function is deprecated.  Use get_frame_register_value instead,
   which provides more accurate information.

   Find and return the value of REGNUM for the specified stack frame.
   The number of bytes copied is REGISTER_SIZE (REGNUM).

   Returns 0 if the register value could not be found.  */

bool
deprecated_frame_register_read (frame_info *frame, int regnum,
				gdb_byte *myaddr)
{
  int optimized;
  int unavailable;
  enum lval_type lval;
  CORE_ADDR addr;
  int realnum;

  frame_register (frame, regnum, &optimized, &unavailable,
		  &lval, &addr, &realnum, myaddr);

  return !optimized && !unavailable;
}

bool
get_frame_register_bytes (frame_info *frame, int regnum,
			  CORE_ADDR offset, int len, gdb_byte *myaddr,
			  int *optimizedp, int *unavailablep)
{
  struct gdbarch *gdbarch = get_frame_arch (frame);
  int i;
  int maxsize;
  int numregs;

  /* Skip registers wholly inside of OFFSET.  */
  while (offset >= register_size (gdbarch, regnum))
    {
      offset -= register_size (gdbarch, regnum);
      regnum++;
    }

  /* Ensure that we will not read beyond the end of the register file.
     This can only ever happen if the debug information is bad.  */
  maxsize = -offset;
  numregs = gdbarch_num_cooked_regs (gdbarch);
  for (i = regnum; i < numregs; i++)
    {
      int thissize = register_size (gdbarch, i);

      if (thissize == 0)
	break;	/* This register is not available on this architecture.  */
      maxsize += thissize;
    }
  if (len > maxsize)
    error (_("Bad debug information detected: "
	     "Attempt to read %d bytes from registers."), len);

  /* Copy the data.  */
  while (len > 0)
    {
      int curr_len = register_size (gdbarch, regnum) - offset;

      if (curr_len > len)
	curr_len = len;

      if (curr_len == register_size (gdbarch, regnum))
	{
	  enum lval_type lval;
	  CORE_ADDR addr;
	  int realnum;

	  frame_register (frame, regnum, optimizedp, unavailablep,
			  &lval, &addr, &realnum, myaddr);
	  if (*optimizedp || *unavailablep)
	    return false;
	}
      else
	{
	  struct value *value = frame_unwind_register_value (frame->next,
							     regnum);
	  gdb_assert (value != NULL);
	  *optimizedp = value_optimized_out (value);
	  *unavailablep = !value_entirely_available (value);

	  if (*optimizedp || *unavailablep)
	    {
	      release_value (value);
	      return false;
	    }

	  memcpy (myaddr, value_contents_all (value) + offset, curr_len);
	  release_value (value);
	}

      myaddr += curr_len;
      len -= curr_len;
      offset = 0;
      regnum++;
    }

  *optimizedp = 0;
  *unavailablep = 0;

  return true;
}

void
put_frame_register_bytes (struct frame_info *frame, int regnum,
			  CORE_ADDR offset, int len, const gdb_byte *myaddr)
{
  struct gdbarch *gdbarch = get_frame_arch (frame);

  /* Skip registers wholly inside of OFFSET.  */
  while (offset >= register_size (gdbarch, regnum))
    {
      offset -= register_size (gdbarch, regnum);
      regnum++;
    }

  /* Copy the data.  */
  while (len > 0)
    {
      int curr_len = register_size (gdbarch, regnum) - offset;

      if (curr_len > len)
	curr_len = len;

      if (curr_len == register_size (gdbarch, regnum))
	{
	  put_frame_register (frame, regnum, myaddr);
	}
      else
	{
	  struct value *value = frame_unwind_register_value (frame->next,
							     regnum);
	  gdb_assert (value != NULL);

	  memcpy ((char *) value_contents_writeable (value) + offset, myaddr,
		  curr_len);
	  put_frame_register (frame, regnum, value_contents_raw (value));
	  release_value (value);
	}

      myaddr += curr_len;
      len -= curr_len;
      offset = 0;
      regnum++;
    }
}

/* Create a sentinel frame.  */

static struct frame_info *
create_sentinel_frame (struct program_space *pspace, struct regcache *regcache)
{
  struct frame_info *frame = FRAME_OBSTACK_ZALLOC (struct frame_info);

  frame->level = -1;
  frame->pspace = pspace;
  frame->aspace = regcache->aspace ();
  /* Explicitly initialize the sentinel frame's cache.  Provide it
     with the underlying regcache.  In the future additional
     information, such as the frame's thread will be added.  */
  frame->prologue_cache = sentinel_frame_cache (regcache);
  /* For the moment there is only one sentinel frame implementation.  */
  frame->unwind = &sentinel_frame_unwind;
  /* Link this frame back to itself.  The frame is self referential
     (the unwound PC is the same as the pc), so make it so.  */
  frame->next = frame;
  /* The sentinel frame has a special ID.  */
  frame->this_id.p = frame_id_status::COMPUTED;
  frame->this_id.value = sentinel_frame_id;
  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "{ create_sentinel_frame (...) -> ");
      fprint_frame (gdb_stdlog, frame);
      fprintf_unfiltered (gdb_stdlog, " }\n");
    }
  return frame;
}

/* Cache for frame addresses already read by gdb.  Valid only while
   inferior is stopped.  Control variables for the frame cache should
   be local to this module.  */

static struct obstack frame_cache_obstack;

void *
frame_obstack_zalloc (unsigned long size)
{
  void *data = obstack_alloc (&frame_cache_obstack, size);

  memset (data, 0, size);
  return data;
}

static struct frame_info *get_prev_frame_always_1 (struct frame_info *this_frame);

struct frame_info *
get_current_frame (void)
{
  struct frame_info *current_frame;

  /* First check, and report, the lack of registers.  Having GDB
     report "No stack!" or "No memory" when the target doesn't even
     have registers is very confusing.  Besides, "printcmd.exp"
     explicitly checks that ``print $pc'' with no registers prints "No
     registers".  */
  if (!target_has_registers ())
    error (_("No registers."));
  if (!target_has_stack ())
    error (_("No stack."));
  if (!target_has_memory ())
    error (_("No memory."));
  /* Traceframes are effectively a substitute for the live inferior.  */
  if (get_traceframe_number () < 0)
    validate_registers_access ();

  if (sentinel_frame == NULL)
    sentinel_frame =
      create_sentinel_frame (current_program_space, get_current_regcache ());

  /* Set the current frame before computing the frame id, to avoid
     recursion inside compute_frame_id, in case the frame's
     unwinder decides to do a symbol lookup (which depends on the
     selected frame's block).

     This call must always succeed.  In particular, nothing inside
     get_prev_frame_always_1 should try to unwind from the
     sentinel frame, because that could fail/throw, and we always
     want to leave with the current frame created and linked in --
     we should never end up with the sentinel frame as outermost
     frame.  */
  current_frame = get_prev_frame_always_1 (sentinel_frame);
  gdb_assert (current_frame != NULL);

  return current_frame;
}

/* The "selected" stack frame is used by default for local and arg
   access.  May be zero, for no selected frame.  */

static struct frame_info *selected_frame;

bool
has_stack_frames ()
{
  if (!target_has_registers () || !target_has_stack ()
      || !target_has_memory ())
    return false;

  /* Traceframes are effectively a substitute for the live inferior.  */
  if (get_traceframe_number () < 0)
    {
      /* No current inferior, no frame.  */
      if (inferior_ptid == null_ptid)
	return false;

      thread_info *tp = inferior_thread ();
      /* Don't try to read from a dead thread.  */
      if (tp->state == THREAD_EXITED)
	return false;

      /* ... or from a spinning thread.  */
      if (tp->executing)
	return false;
    }

  return true;
}

/* Return the selected frame.  Always non-NULL (unless there isn't an
   inferior sufficient for creating a frame) in which case an error is
   thrown.  */

struct frame_info *
get_selected_frame (const char *message)
{
  if (selected_frame == NULL)
    {
      if (message != NULL && !has_stack_frames ())
	error (("%s"), message);
      /* Hey!  Don't trust this.  It should really be re-finding the
	 last selected frame of the currently selected thread.  This,
	 though, is better than nothing.  */
      select_frame (get_current_frame ());
    }
  /* There is always a frame.  */
  gdb_assert (selected_frame != NULL);
  return selected_frame;
}

/* If there is a selected frame, return it.  Otherwise, return NULL.  */

struct frame_info *
get_selected_frame_if_set (void)
{
  return selected_frame;
}

/* This is a variant of get_selected_frame() which can be called when
   the inferior does not have a frame; in that case it will return
   NULL instead of calling error().  */

struct frame_info *
deprecated_safe_get_selected_frame (void)
{
  if (!has_stack_frames ())
    return NULL;
  return get_selected_frame (NULL);
}

/* Select frame FI (or NULL - to invalidate the current frame).  */

void
select_frame (struct frame_info *fi)
{
  selected_frame = fi;
  /* NOTE: cagney/2002-05-04: FI can be NULL.  This occurs when the
     frame is being invalidated.  */

  /* FIXME: kseitz/2002-08-28: It would be nice to call
     selected_frame_level_changed_event() right here, but due to limitations
     in the current interfaces, we would end up flooding UIs with events
     because select_frame() is used extensively internally.

     Once we have frame-parameterized frame (and frame-related) commands,
     the event notification can be moved here, since this function will only
     be called when the user's selected frame is being changed.  */

  /* Ensure that symbols for this frame are read in.  Also, determine the
     source language of this frame, and switch to it if desired.  */
  if (fi)
    {
      CORE_ADDR pc;

      /* We retrieve the frame's symtab by using the frame PC.
	 However we cannot use the frame PC as-is, because it usually
	 points to the instruction following the "call", which is
	 sometimes the first instruction of another function.  So we
	 rely on get_frame_address_in_block() which provides us with a
	 PC which is guaranteed to be inside the frame's code
	 block.  */
      if (get_frame_address_in_block_if_available (fi, &pc))
	{
	  struct compunit_symtab *cust = find_pc_compunit_symtab (pc);

	  if (cust != NULL
	      && compunit_language (cust) != current_language->la_language
	      && compunit_language (cust) != language_unknown
	      && language_mode == language_mode_auto)
	    set_language (compunit_language (cust));
	}
    }
}

/* Create an arbitrary (i.e. address specified by user) or innermost frame.
   Always returns a non-NULL value.  */

struct frame_info *
create_new_frame (CORE_ADDR addr, CORE_ADDR pc)
{
  struct frame_info *fi;

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog,
			  "{ create_new_frame (addr=%s, pc=%s) ",
			  hex_string (addr), hex_string (pc));
    }

  fi = FRAME_OBSTACK_ZALLOC (struct frame_info);

  fi->next = create_sentinel_frame (current_program_space,
				    get_current_regcache ());

  /* Set/update this frame's cached PC value, found in the next frame.
     Do this before looking for this frame's unwinder.  A sniffer is
     very likely to read this, and the corresponding unwinder is
     entitled to rely that the PC doesn't magically change.  */
  fi->next->prev_pc.value = pc;
  fi->next->prev_pc.status = CC_VALUE;

  /* We currently assume that frame chain's can't cross spaces.  */
  fi->pspace = fi->next->pspace;
  fi->aspace = fi->next->aspace;

  /* Select/initialize both the unwind function and the frame's type
     based on the PC.  */
  frame_unwind_find_by_frame (fi, &fi->prologue_cache);

  fi->this_id.p = frame_id_status::COMPUTED;
  fi->this_id.value = frame_id_build (addr, pc);

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "-> ");
      fprint_frame (gdb_stdlog, fi);
      fprintf_unfiltered (gdb_stdlog, " }\n");
    }

  return fi;
}

/* Return the frame that THIS_FRAME calls (NULL if THIS_FRAME is the
   innermost frame).  Be careful to not fall off the bottom of the
   frame chain and onto the sentinel frame.  */

struct frame_info *
get_next_frame (struct frame_info *this_frame)
{
  if (this_frame->level > 0)
    return this_frame->next;
  else
    return NULL;
}

/* Return the frame that THIS_FRAME calls.  If THIS_FRAME is the
   innermost (i.e. current) frame, return the sentinel frame.  Thus,
   unlike get_next_frame(), NULL will never be returned.  */

struct frame_info *
get_next_frame_sentinel_okay (struct frame_info *this_frame)
{
  gdb_assert (this_frame != NULL);

  /* Note that, due to the manner in which the sentinel frame is
     constructed, this_frame->next still works even when this_frame
     is the sentinel frame.  But we disallow it here anyway because
     calling get_next_frame_sentinel_okay() on the sentinel frame
     is likely a coding error.  */
  gdb_assert (this_frame != sentinel_frame);

  return this_frame->next;
}

/* Observer for the target_changed event.  */

static void
frame_observer_target_changed (struct target_ops *target)
{
  reinit_frame_cache ();
}

/* Flush the entire frame cache.  */

void
reinit_frame_cache (void)
{
  struct frame_info *fi;

  ++frame_cache_generation;

  /* Tear down all frame caches.  */
  for (fi = sentinel_frame; fi != NULL; fi = fi->prev)
    {
      if (fi->prologue_cache && fi->unwind->dealloc_cache)
	fi->unwind->dealloc_cache (fi, fi->prologue_cache);
      if (fi->base_cache && fi->base->unwind->dealloc_cache)
	fi->base->unwind->dealloc_cache (fi, fi->base_cache);
    }

  /* Since we can't really be sure what the first object allocated was.  */
  obstack_free (&frame_cache_obstack, 0);
  obstack_init (&frame_cache_obstack);

  if (sentinel_frame != NULL)
    annotate_frames_invalid ();

  sentinel_frame = NULL;		/* Invalidate cache */
  select_frame (NULL);
  frame_stash_invalidate ();
  if (frame_debug)
    fprintf_unfiltered (gdb_stdlog, "{ reinit_frame_cache () }\n");
}

/* Find where a register is saved (in memory or another register).
   The result of frame_register_unwind is just where it is saved
   relative to this particular frame.  */

static void
frame_register_unwind_location (struct frame_info *this_frame, int regnum,
				int *optimizedp, enum lval_type *lvalp,
				CORE_ADDR *addrp, int *realnump)
{
  gdb_assert (this_frame == NULL || this_frame->level >= 0);

  while (this_frame != NULL)
    {
      int unavailable;

      frame_register_unwind (this_frame, regnum, optimizedp, &unavailable,
			     lvalp, addrp, realnump, NULL);

      if (*optimizedp)
	break;

      if (*lvalp != lval_register)
	break;

      regnum = *realnump;
      this_frame = get_next_frame (this_frame);
    }
}

/* Get the previous raw frame, and check that it is not identical to
   same other frame frame already in the chain.  If it is, there is
   most likely a stack cycle, so we discard it, and mark THIS_FRAME as
   outermost, with UNWIND_SAME_ID stop reason.  Unlike the other
   validity tests, that compare THIS_FRAME and the next frame, we do
   this right after creating the previous frame, to avoid ever ending
   up with two frames with the same id in the frame chain.  */

static struct frame_info *
get_prev_frame_if_no_cycle (struct frame_info *this_frame)
{
  struct frame_info *prev_frame;

  prev_frame = get_prev_frame_raw (this_frame);

  /* Don't compute the frame id of the current frame yet.  Unwinding
     the sentinel frame can fail (e.g., if the thread is gone and we
     can't thus read its registers).  If we let the cycle detection
     code below try to compute a frame ID, then an error thrown from
     within the frame ID computation would result in the sentinel
     frame as outermost frame, which is bogus.  Instead, we'll compute
     the current frame's ID lazily in get_frame_id.  Note that there's
     no point in doing cycle detection when there's only one frame, so
     nothing is lost here.  */
  if (prev_frame->level == 0)
    return prev_frame;

  unsigned int entry_generation = get_frame_cache_generation ();

  try
    {
      compute_frame_id (prev_frame);
      if (!frame_stash_add (prev_frame))
	{
	  /* Another frame with the same id was already in the stash.  We just
	     detected a cycle.  */
	  if (frame_debug)
	    {
	      fprintf_unfiltered (gdb_stdlog, "-> ");
	      fprint_frame (gdb_stdlog, NULL);
	      fprintf_unfiltered (gdb_stdlog, " // this frame has same ID }\n");
	    }
	  this_frame->stop_reason = UNWIND_SAME_ID;
	  /* Unlink.  */
	  prev_frame->next = NULL;
	  this_frame->prev = NULL;
	  prev_frame = NULL;
	}
    }
  catch (const gdb_exception &ex)
    {
      if (get_frame_cache_generation () == entry_generation)
	{
	  prev_frame->next = NULL;
	  this_frame->prev = NULL;
	}

      throw;
    }

  return prev_frame;
}

/* Helper function for get_prev_frame_always, this is called inside a
   TRY_CATCH block.  Return the frame that called THIS_FRAME or NULL if
   there is no such frame.  This may throw an exception.  */

static struct frame_info *
get_prev_frame_always_1 (struct frame_info *this_frame)
{
  struct gdbarch *gdbarch;

  gdb_assert (this_frame != NULL);
  gdbarch = get_frame_arch (this_frame);

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "{ get_prev_frame_always (this_frame=");
      if (this_frame != NULL)
	fprintf_unfiltered (gdb_stdlog, "%d", this_frame->level);
      else
	fprintf_unfiltered (gdb_stdlog, "<NULL>");
      fprintf_unfiltered (gdb_stdlog, ") ");
    }

  /* Only try to do the unwind once.  */
  if (this_frame->prev_p)
    {
      if (frame_debug)
	{
	  fprintf_unfiltered (gdb_stdlog, "-> ");
	  fprint_frame (gdb_stdlog, this_frame->prev);
	  fprintf_unfiltered (gdb_stdlog, " // cached \n");
	}
      return this_frame->prev;
    }

  /* If the frame unwinder hasn't been selected yet, we must do so
     before setting prev_p; otherwise the check for misbehaved
     sniffers will think that this frame's sniffer tried to unwind
     further (see frame_cleanup_after_sniffer).  */
  if (this_frame->unwind == NULL)
    frame_unwind_find_by_frame (this_frame, &this_frame->prologue_cache);

  this_frame->prev_p = true;
  this_frame->stop_reason = UNWIND_NO_REASON;

  /* If we are unwinding from an inline frame, all of the below tests
     were already performed when we unwound from the next non-inline
     frame.  We must skip them, since we can not get THIS_FRAME's ID
     until we have unwound all the way down to the previous non-inline
     frame.  */
  if (get_frame_type (this_frame) == INLINE_FRAME)
    return get_prev_frame_if_no_cycle (this_frame);

  /* Check that this frame is unwindable.  If it isn't, don't try to
     unwind to the prev frame.  */
  this_frame->stop_reason
    = this_frame->unwind->stop_reason (this_frame,
				       &this_frame->prologue_cache);

  if (this_frame->stop_reason != UNWIND_NO_REASON)
    {
      if (frame_debug)
	{
	  enum unwind_stop_reason reason = this_frame->stop_reason;

	  fprintf_unfiltered (gdb_stdlog, "-> ");
	  fprint_frame (gdb_stdlog, NULL);
	  fprintf_unfiltered (gdb_stdlog, " // %s }\n",
			      frame_stop_reason_symbol_string (reason));
	}
      return NULL;
    }

  /* Check that this frame's ID isn't inner to (younger, below, next)
     the next frame.  This happens when a frame unwind goes backwards.
     This check is valid only if this frame and the next frame are NORMAL.
     See the comment at frame_id_inner for details.  */
  if (get_frame_type (this_frame) == NORMAL_FRAME
      && this_frame->next->unwind->type == NORMAL_FRAME
      && frame_id_inner (get_frame_arch (this_frame->next),
			 get_frame_id (this_frame),
			 get_frame_id (this_frame->next)))
    {
      CORE_ADDR this_pc_in_block;
      struct minimal_symbol *morestack_msym;
      const char *morestack_name = NULL;
      
      /* gcc -fsplit-stack __morestack can continue the stack anywhere.  */
      this_pc_in_block = get_frame_address_in_block (this_frame);
      morestack_msym = lookup_minimal_symbol_by_pc (this_pc_in_block).minsym;
      if (morestack_msym)
	morestack_name = morestack_msym->linkage_name ();
      if (!morestack_name || strcmp (morestack_name, "__morestack") != 0)
	{
	  if (frame_debug)
	    {
	      fprintf_unfiltered (gdb_stdlog, "-> ");
	      fprint_frame (gdb_stdlog, NULL);
	      fprintf_unfiltered (gdb_stdlog,
				  " // this frame ID is inner }\n");
	    }
	  this_frame->stop_reason = UNWIND_INNER_ID;
	  return NULL;
	}
    }

  /* Check that this and the next frame do not unwind the PC register
     to the same memory location.  If they do, then even though they
     have different frame IDs, the new frame will be bogus; two
     functions can't share a register save slot for the PC.  This can
     happen when the prologue analyzer finds a stack adjustment, but
     no PC save.

     This check does assume that the "PC register" is roughly a
     traditional PC, even if the gdbarch_unwind_pc method adjusts
     it (we do not rely on the value, only on the unwound PC being
     dependent on this value).  A potential improvement would be
     to have the frame prev_pc method and the gdbarch unwind_pc
     method set the same lval and location information as
     frame_register_unwind.  */
  if (this_frame->level > 0
      && gdbarch_pc_regnum (gdbarch) >= 0
      && get_frame_type (this_frame) == NORMAL_FRAME
      && (get_frame_type (this_frame->next) == NORMAL_FRAME
	  || get_frame_type (this_frame->next) == INLINE_FRAME))
    {
      int optimized, realnum, nrealnum;
      enum lval_type lval, nlval;
      CORE_ADDR addr, naddr;

      frame_register_unwind_location (this_frame,
				      gdbarch_pc_regnum (gdbarch),
				      &optimized, &lval, &addr, &realnum);
      frame_register_unwind_location (get_next_frame (this_frame),
				      gdbarch_pc_regnum (gdbarch),
				      &optimized, &nlval, &naddr, &nrealnum);

      if ((lval == lval_memory && lval == nlval && addr == naddr)
	  || (lval == lval_register && lval == nlval && realnum == nrealnum))
	{
	  if (frame_debug)
	    {
	      fprintf_unfiltered (gdb_stdlog, "-> ");
	      fprint_frame (gdb_stdlog, NULL);
	      fprintf_unfiltered (gdb_stdlog, " // no saved PC }\n");
	    }

	  this_frame->stop_reason = UNWIND_NO_SAVED_PC;
	  this_frame->prev = NULL;
	  return NULL;
	}
    }

  return get_prev_frame_if_no_cycle (this_frame);
}

/* Return a "struct frame_info" corresponding to the frame that called
   THIS_FRAME.  Returns NULL if there is no such frame.

   Unlike get_prev_frame, this function always tries to unwind the
   frame.  */

struct frame_info *
get_prev_frame_always (struct frame_info *this_frame)
{
  struct frame_info *prev_frame = NULL;

  try
    {
      prev_frame = get_prev_frame_always_1 (this_frame);
    }
  catch (const gdb_exception_error &ex)
    {
      if (ex.error == MEMORY_ERROR)
	{
	  this_frame->stop_reason = UNWIND_MEMORY_ERROR;
	  if (ex.message != NULL)
	    {
	      char *stop_string;
	      size_t size;

	      /* The error needs to live as long as the frame does.
	         Allocate using stack local STOP_STRING then assign the
	         pointer to the frame, this allows the STOP_STRING on the
	         frame to be of type 'const char *'.  */
	      size = ex.message->size () + 1;
	      stop_string = (char *) frame_obstack_zalloc (size);
	      memcpy (stop_string, ex.what (), size);
	      this_frame->stop_string = stop_string;
	    }
	  prev_frame = NULL;
	}
      else
	throw;
    }

  return prev_frame;
}

/* Construct a new "struct frame_info" and link it previous to
   this_frame.  */

static struct frame_info *
get_prev_frame_raw (struct frame_info *this_frame)
{
  struct frame_info *prev_frame;

  /* Allocate the new frame but do not wire it in to the frame chain.
     Some (bad) code in INIT_FRAME_EXTRA_INFO tries to look along
     frame->next to pull some fancy tricks (of course such code is, by
     definition, recursive).  Try to prevent it.

     There is no reason to worry about memory leaks, should the
     remainder of the function fail.  The allocated memory will be
     quickly reclaimed when the frame cache is flushed, and the `we've
     been here before' check above will stop repeated memory
     allocation calls.  */
  prev_frame = FRAME_OBSTACK_ZALLOC (struct frame_info);
  prev_frame->level = this_frame->level + 1;

  /* For now, assume we don't have frame chains crossing address
     spaces.  */
  prev_frame->pspace = this_frame->pspace;
  prev_frame->aspace = this_frame->aspace;

  /* Don't yet compute ->unwind (and hence ->type).  It is computed
     on-demand in get_frame_type, frame_register_unwind, and
     get_frame_id.  */

  /* Don't yet compute the frame's ID.  It is computed on-demand by
     get_frame_id().  */

  /* The unwound frame ID is validate at the start of this function,
     as part of the logic to decide if that frame should be further
     unwound, and not here while the prev frame is being created.
     Doing this makes it possible for the user to examine a frame that
     has an invalid frame ID.

     Some very old VAX code noted: [...]  For the sake of argument,
     suppose that the stack is somewhat trashed (which is one reason
     that "info frame" exists).  So, return 0 (indicating we don't
     know the address of the arglist) if we don't know what frame this
     frame calls.  */

  /* Link it in.  */
  this_frame->prev = prev_frame;
  prev_frame->next = this_frame;

  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "-> ");
      fprint_frame (gdb_stdlog, prev_frame);
      fprintf_unfiltered (gdb_stdlog, " }\n");
    }

  return prev_frame;
}

/* Debug routine to print a NULL frame being returned.  */

static void
frame_debug_got_null_frame (struct frame_info *this_frame,
			    const char *reason)
{
  if (frame_debug)
    {
      fprintf_unfiltered (gdb_stdlog, "{ get_prev_frame (this_frame=");
      if (this_frame != NULL)
	fprintf_unfiltered (gdb_stdlog, "%d", this_frame->level);
      else
	fprintf_unfiltered (gdb_stdlog, "<NULL>");
      fprintf_unfiltered (gdb_stdlog, ") -> // %s}\n", reason);
    }
}

/* Is this (non-sentinel) frame in the "main"() function?  */

static bool
inside_main_func (frame_info *this_frame)
{
  if (symfile_objfile == nullptr)
    return false;

  CORE_ADDR sym_addr;
  const char *name = main_name ();
  bound_minimal_symbol msymbol
    = lookup_minimal_symbol (name, NULL, symfile_objfile);
  if (msymbol.minsym == nullptr)
    {
      /* In some language (for example Fortran) there will be no minimal
	 symbol with the name of the main function.  In this case we should
	 search the full symbols to see if we can find a match.  */
      struct block_symbol bs = lookup_symbol (name, NULL, VAR_DOMAIN, 0);
      if (bs.symbol == nullptr)
	return false;

      const struct block *block = SYMBOL_BLOCK_VALUE (bs.symbol);
      gdb_assert (block != nullptr);
      sym_addr = BLOCK_START (block);
    }
  else
    sym_addr = BMSYMBOL_VALUE_ADDRESS (msymbol);

  /* Convert any function descriptor addresses into the actual function
     code address.  */
  sym_addr
    = gdbarch_convert_from_func_ptr_addr (get_frame_arch (this_frame),
					  sym_addr, current_top_target ());

  return sym_addr == get_frame_func (this_frame);
}

/* Test whether THIS_FRAME is inside the process entry point function.  */

static bool
inside_entry_func (frame_info *this_frame)
{
  CORE_ADDR entry_point;

  if (!entry_point_address_query (&entry_point))
    return false;

  return get_frame_func (this_frame) == entry_point;
}

/* Return a structure containing various interesting information about
   the frame that called THIS_FRAME.  Returns NULL if there is entier
   no such frame or the frame fails any of a set of target-independent
   condition that should terminate the frame chain (e.g., as unwinding
   past main()).

   This function should not contain target-dependent tests, such as
   checking whether the program-counter is zero.  */

struct frame_info *
get_prev_frame (struct frame_info *this_frame)
{
  CORE_ADDR frame_pc;
  int frame_pc_p;

  /* There is always a frame.  If this assertion fails, suspect that
     something should be calling get_selected_frame() or
     get_current_frame().  */
  gdb_assert (this_frame != NULL);
  
  /* If this_frame is the current frame, then compute and stash
     its frame id prior to fetching and computing the frame id of the
     previous frame.  Otherwise, the cycle detection code in
     get_prev_frame_if_no_cycle() will not work correctly.  When
     get_frame_id() is called later on, an assertion error will
     be triggered in the event of a cycle between the current
     frame and its previous frame.  */
  if (this_frame->level == 0)
    get_frame_id (this_frame);

  frame_pc_p = get_frame_pc_if_available (this_frame, &frame_pc);

  /* tausq/2004-12-07: Dummy frames are skipped because it doesn't make much
     sense to stop unwinding at a dummy frame.  One place where a dummy
     frame may have an address "inside_main_func" is on HPUX.  On HPUX, the
     pcsqh register (space register for the instruction at the head of the
     instruction queue) cannot be written directly; the only way to set it
     is to branch to code that is in the target space.  In order to implement
     frame dummies on HPUX, the called function is made to jump back to where 
     the inferior was when the user function was called.  If gdb was inside 
     the main function when we created the dummy frame, the dummy frame will 
     point inside the main function.  */
  if (this_frame->level >= 0
      && get_frame_type (this_frame) == NORMAL_FRAME
      && !user_set_backtrace_options.backtrace_past_main
      && frame_pc_p
      && inside_main_func (this_frame))
    /* Don't unwind past main().  Note, this is done _before_ the
       frame has been marked as previously unwound.  That way if the
       user later decides to enable unwinds past main(), that will
       automatically happen.  */
    {
      frame_debug_got_null_frame (this_frame, "inside main func");
      return NULL;
    }

  /* If the user's backtrace limit has been exceeded, stop.  We must
     add two to the current level; one of those accounts for backtrace_limit
     being 1-based and the level being 0-based, and the other accounts for
     the level of the new frame instead of the level of the current
     frame.  */
  if (this_frame->level + 2 > user_set_backtrace_options.backtrace_limit)
    {
      frame_debug_got_null_frame (this_frame, "backtrace limit exceeded");
      return NULL;
    }

  /* If we're already inside the entry function for the main objfile,
     then it isn't valid.  Don't apply this test to a dummy frame -
     dummy frame PCs typically land in the entry func.  Don't apply
     this test to the sentinel frame.  Sentinel frames should always
     be allowed to unwind.  */
  /* NOTE: cagney/2003-07-07: Fixed a bug in inside_main_func() -
     wasn't checking for "main" in the minimal symbols.  With that
     fixed asm-source tests now stop in "main" instead of halting the
     backtrace in weird and wonderful ways somewhere inside the entry
     file.  Suspect that tests for inside the entry file/func were
     added to work around that (now fixed) case.  */
  /* NOTE: cagney/2003-07-15: danielj (if I'm reading it right)
     suggested having the inside_entry_func test use the
     inside_main_func() msymbol trick (along with entry_point_address()
     I guess) to determine the address range of the start function.
     That should provide a far better stopper than the current
     heuristics.  */
  /* NOTE: tausq/2004-10-09: this is needed if, for example, the compiler
     applied tail-call optimizations to main so that a function called 
     from main returns directly to the caller of main.  Since we don't
     stop at main, we should at least stop at the entry point of the
     application.  */
  if (this_frame->level >= 0
      && get_frame_type (this_frame) == NORMAL_FRAME
      && !user_set_backtrace_options.backtrace_past_entry
      && frame_pc_p
      && inside_entry_func (this_frame))
    {
      frame_debug_got_null_frame (this_frame, "inside entry func");
      return NULL;
    }

  /* Assume that the only way to get a zero PC is through something
     like a SIGSEGV or a dummy frame, and hence that NORMAL frames
     will never unwind a zero PC.  */
  if (this_frame->level > 0
      && (get_frame_type (this_frame) == NORMAL_FRAME
	  || get_frame_type (this_frame) == INLINE_FRAME)
      && get_frame_type (get_next_frame (this_frame)) == NORMAL_FRAME
      && frame_pc_p && frame_pc == 0)
    {
      frame_debug_got_null_frame (this_frame, "zero PC");
      return NULL;
    }

  return get_prev_frame_always (this_frame);
}

struct frame_id
get_prev_frame_id_by_id (struct frame_id id)
{
  struct frame_id prev_id;
  struct frame_info *frame;
  
  frame = frame_find_by_id (id);

  if (frame != NULL)
    prev_id = get_frame_id (get_prev_frame (frame));
  else
    prev_id = null_frame_id;

  return prev_id;
}

CORE_ADDR
get_frame_pc (struct frame_info *frame)
{
  gdb_assert (frame->next != NULL);
  return frame_unwind_pc (frame->next);
}

bool
get_frame_pc_if_available (frame_info *frame, CORE_ADDR *pc)
{

  gdb_assert (frame->next != NULL);

  try
    {
      *pc = frame_unwind_pc (frame->next);
    }
  catch (const gdb_exception_error &ex)
    {
      if (ex.error == NOT_AVAILABLE_ERROR)
	return false;
      else
	throw;
    }

  return true;
}

/* Return an address that falls within THIS_FRAME's code block.  */

CORE_ADDR
get_frame_address_in_block (struct frame_info *this_frame)
{
  /* A draft address.  */
  CORE_ADDR pc = get_frame_pc (this_frame);

  struct frame_info *next_frame = this_frame->next;

  /* Calling get_frame_pc returns the resume address for THIS_FRAME.
     Normally the resume address is inside the body of the function
     associated with THIS_FRAME, but there is a special case: when
     calling a function which the compiler knows will never return
     (for instance abort), the call may be the very last instruction
     in the calling function.  The resume address will point after the
     call and may be at the beginning of a different function
     entirely.

     If THIS_FRAME is a signal frame or dummy frame, then we should
     not adjust the unwound PC.  For a dummy frame, GDB pushed the
     resume address manually onto the stack.  For a signal frame, the
     OS may have pushed the resume address manually and invoked the
     handler (e.g. GNU/Linux), or invoked the trampoline which called
     the signal handler - but in either case the signal handler is
     expected to return to the trampoline.  So in both of these
     cases we know that the resume address is executable and
     related.  So we only need to adjust the PC if THIS_FRAME
     is a normal function.

     If the program has been interrupted while THIS_FRAME is current,
     then clearly the resume address is inside the associated
     function.  There are three kinds of interruption: debugger stop
     (next frame will be SENTINEL_FRAME), operating system
     signal or exception (next frame will be SIGTRAMP_FRAME),
     or debugger-induced function call (next frame will be
     DUMMY_FRAME).  So we only need to adjust the PC if
     NEXT_FRAME is a normal function.

     We check the type of NEXT_FRAME first, since it is already
     known; frame type is determined by the unwinder, and since
     we have THIS_FRAME we've already selected an unwinder for
     NEXT_FRAME.

     If the next frame is inlined, we need to keep going until we find
     the real function - for instance, if a signal handler is invoked
     while in an inlined function, then the code address of the
     "calling" normal function should not be adjusted either.  */

  while (get_frame_type (next_frame) == INLINE_FRAME)
    next_frame = next_frame->next;

  if ((get_frame_type (next_frame) == NORMAL_FRAME
       || get_frame_type (next_frame) == TAILCALL_FRAME)
      && (get_frame_type (this_frame) == NORMAL_FRAME
	  || get_frame_type (this_frame) == TAILCALL_FRAME
	  || get_frame_type (this_frame) == INLINE_FRAME))
    return pc - 1;

  return pc;
}

bool
get_frame_address_in_block_if_available (frame_info *this_frame,
					 CORE_ADDR *pc)
{

  try
    {
      *pc = get_frame_address_in_block (this_frame);
    }
  catch (const gdb_exception_error &ex)
    {
      if (ex.error == NOT_AVAILABLE_ERROR)
	return false;
      throw;
    }

  return true;
}

symtab_and_line
find_frame_sal (frame_info *frame)
{
  struct frame_info *next_frame;
  int notcurrent;
  CORE_ADDR pc;

  if (frame_inlined_callees (frame) > 0)
    {
      struct symbol *sym;

      /* If the current frame has some inlined callees, and we have a next
	 frame, then that frame must be an inlined frame.  In this case
	 this frame's sal is the "call site" of the next frame's inlined
	 function, which can not be inferred from get_frame_pc.  */
      next_frame = get_next_frame (frame);
      if (next_frame)
	sym = get_frame_function (next_frame);
      else
	sym = inline_skipped_symbol (inferior_thread ());

      /* If frame is inline, it certainly has symbols.  */
      gdb_assert (sym);

      symtab_and_line sal;
      if (SYMBOL_LINE (sym) != 0)
	{
	  sal.symtab = symbol_symtab (sym);
	  sal.line = SYMBOL_LINE (sym);
	}
      else
	/* If the symbol does not have a location, we don't know where
	   the call site is.  Do not pretend to.  This is jarring, but
	   we can't do much better.  */
	sal.pc = get_frame_pc (frame);

      sal.pspace = get_frame_program_space (frame);
      return sal;
    }

  /* If FRAME is not the innermost frame, that normally means that
     FRAME->pc points at the return instruction (which is *after* the
     call instruction), and we want to get the line containing the
     call (because the call is where the user thinks the program is).
     However, if the next frame is either a SIGTRAMP_FRAME or a
     DUMMY_FRAME, then the next frame will contain a saved interrupt
     PC and such a PC indicates the current (rather than next)
     instruction/line, consequently, for such cases, want to get the
     line containing fi->pc.  */
  if (!get_frame_pc_if_available (frame, &pc))
    return {};

  notcurrent = (pc != get_frame_address_in_block (frame));
  return find_pc_line (pc, notcurrent);
}

/* Per "frame.h", return the ``address'' of the frame.  Code should
   really be using get_frame_id().  */
CORE_ADDR
get_frame_base (struct frame_info *fi)
{
  return get_frame_id (fi).stack_addr;
}

/* High-level offsets into the frame.  Used by the debug info.  */

CORE_ADDR
get_frame_base_address (struct frame_info *fi)
{
  if (get_frame_type (fi) != NORMAL_FRAME)
    return 0;
  if (fi->base == NULL)
    fi->base = frame_base_find_by_frame (fi);
  /* Sneaky: If the low-level unwind and high-level base code share a
     common unwinder, let them share the prologue cache.  */
  if (fi->base->unwind == fi->unwind)
    return fi->base->this_base (fi, &fi->prologue_cache);
  return fi->base->this_base (fi, &fi->base_cache);
}

CORE_ADDR
get_frame_locals_address (struct frame_info *fi)
{
  if (get_frame_type (fi) != NORMAL_FRAME)
    return 0;
  /* If there isn't a frame address method, find it.  */
  if (fi->base == NULL)
    fi->base = frame_base_find_by_frame (fi);
  /* Sneaky: If the low-level unwind and high-level base code share a
     common unwinder, let them share the prologue cache.  */
  if (fi->base->unwind == fi->unwind)
    return fi->base->this_locals (fi, &fi->prologue_cache);
  return fi->base->this_locals (fi, &fi->base_cache);
}

CORE_ADDR
get_frame_args_address (struct frame_info *fi)
{
  if (get_frame_type (fi) != NORMAL_FRAME)
    return 0;
  /* If there isn't a frame address method, find it.  */
  if (fi->base == NULL)
    fi->base = frame_base_find_by_frame (fi);
  /* Sneaky: If the low-level unwind and high-level base code share a
     common unwinder, let them share the prologue cache.  */
  if (fi->base->unwind == fi->unwind)
    return fi->base->this_args (fi, &fi->prologue_cache);
  return fi->base->this_args (fi, &fi->base_cache);
}

/* Return true if the frame unwinder for frame FI is UNWINDER; false
   otherwise.  */

bool
frame_unwinder_is (frame_info *fi, const frame_unwind *unwinder)
{
  if (fi->unwind == nullptr)
    frame_unwind_find_by_frame (fi, &fi->prologue_cache);

  return fi->unwind == unwinder;
}

/* Level of the selected frame: 0 for innermost, 1 for its caller, ...
   or -1 for a NULL frame.  */

int
frame_relative_level (struct frame_info *fi)
{
  if (fi == NULL)
    return -1;
  else
    return fi->level;
}

enum frame_type
get_frame_type (struct frame_info *frame)
{
  if (frame->unwind == NULL)
    /* Initialize the frame's unwinder because that's what
       provides the frame's type.  */
    frame_unwind_find_by_frame (frame, &frame->prologue_cache);
  return frame->unwind->type;
}

struct program_space *
get_frame_program_space (struct frame_info *frame)
{
  return frame->pspace;
}

struct program_space *
frame_unwind_program_space (struct frame_info *this_frame)
{
  gdb_assert (this_frame);

  /* This is really a placeholder to keep the API consistent --- we
     assume for now that we don't have frame chains crossing
     spaces.  */
  return this_frame->pspace;
}

const address_space *
get_frame_address_space (struct frame_info *frame)
{
  return frame->aspace;
}

/* Memory access methods.  */

void
get_frame_memory (struct frame_info *this_frame, CORE_ADDR addr,
		  gdb_byte *buf, int len)
{
  read_memory (addr, buf, len);
}

LONGEST
get_frame_memory_signed (struct frame_info *this_frame, CORE_ADDR addr,
			 int len)
{
  struct gdbarch *gdbarch = get_frame_arch (this_frame);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  return read_memory_integer (addr, len, byte_order);
}

ULONGEST
get_frame_memory_unsigned (struct frame_info *this_frame, CORE_ADDR addr,
			   int len)
{
  struct gdbarch *gdbarch = get_frame_arch (this_frame);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  return read_memory_unsigned_integer (addr, len, byte_order);
}

bool
safe_frame_unwind_memory (struct frame_info *this_frame,
			  CORE_ADDR addr, gdb_byte *buf, int len)
{
  /* NOTE: target_read_memory returns zero on success!  */
  return target_read_memory (addr, buf, len) == 0;
}

/* Architecture methods.  */

struct gdbarch *
get_frame_arch (struct frame_info *this_frame)
{
  return frame_unwind_arch (this_frame->next);
}

struct gdbarch *
frame_unwind_arch (struct frame_info *next_frame)
{
  if (!next_frame->prev_arch.p)
    {
      struct gdbarch *arch;

      if (next_frame->unwind == NULL)
	frame_unwind_find_by_frame (next_frame, &next_frame->prologue_cache);

      if (next_frame->unwind->prev_arch != NULL)
	arch = next_frame->unwind->prev_arch (next_frame,
					      &next_frame->prologue_cache);
      else
	arch = get_frame_arch (next_frame);

      next_frame->prev_arch.arch = arch;
      next_frame->prev_arch.p = true;
      if (frame_debug)
	fprintf_unfiltered (gdb_stdlog,
			    "{ frame_unwind_arch (next_frame=%d) -> %s }\n",
			    next_frame->level,
			    gdbarch_bfd_arch_info (arch)->printable_name);
    }

  return next_frame->prev_arch.arch;
}

struct gdbarch *
frame_unwind_caller_arch (struct frame_info *next_frame)
{
  next_frame = skip_artificial_frames (next_frame);

  /* We must have a non-artificial frame.  The caller is supposed to check
     the result of frame_unwind_caller_id (), which returns NULL_FRAME_ID
     in this case.  */
  gdb_assert (next_frame != NULL);

  return frame_unwind_arch (next_frame);
}

/* Gets the language of FRAME.  */

enum language
get_frame_language (struct frame_info *frame)
{
  CORE_ADDR pc = 0;
  bool pc_p = false;

  gdb_assert (frame!= NULL);

    /* We determine the current frame language by looking up its
       associated symtab.  To retrieve this symtab, we use the frame
       PC.  However we cannot use the frame PC as is, because it
       usually points to the instruction following the "call", which
       is sometimes the first instruction of another function.  So
       we rely on get_frame_address_in_block(), it provides us with
       a PC that is guaranteed to be inside the frame's code
       block.  */

  try
    {
      pc = get_frame_address_in_block (frame);
      pc_p = true;
    }
  catch (const gdb_exception_error &ex)
    {
      if (ex.error != NOT_AVAILABLE_ERROR)
	throw;
    }

  if (pc_p)
    {
      struct compunit_symtab *cust = find_pc_compunit_symtab (pc);

      if (cust != NULL)
	return compunit_language (cust);
    }

  return language_unknown;
}

/* Stack pointer methods.  */

CORE_ADDR
get_frame_sp (struct frame_info *this_frame)
{
  struct gdbarch *gdbarch = get_frame_arch (this_frame);

  /* NOTE drow/2008-06-28: gdbarch_unwind_sp could be converted to
     operate on THIS_FRAME now.  */
  return gdbarch_unwind_sp (gdbarch, this_frame->next);
}

/* Return the reason why we can't unwind past FRAME.  */

enum unwind_stop_reason
get_frame_unwind_stop_reason (struct frame_info *frame)
{
  /* Fill-in STOP_REASON.  */
  get_prev_frame_always (frame);
  gdb_assert (frame->prev_p);

  return frame->stop_reason;
}

/* Return a string explaining REASON.  */

const char *
unwind_stop_reason_to_string (enum unwind_stop_reason reason)
{
  switch (reason)
    {
#define SET(name, description) \
    case name: return _(description);
#include "unwind_stop_reasons.def"
#undef SET

    default:
      internal_error (__FILE__, __LINE__,
		      "Invalid frame stop reason");
    }
}

const char *
frame_stop_reason_string (struct frame_info *fi)
{
  gdb_assert (fi->prev_p);
  gdb_assert (fi->prev == NULL);

  /* Return the specific string if we have one.  */
  if (fi->stop_string != NULL)
    return fi->stop_string;

  /* Return the generic string if we have nothing better.  */
  return unwind_stop_reason_to_string (fi->stop_reason);
}

/* Return the enum symbol name of REASON as a string, to use in debug
   output.  */

static const char *
frame_stop_reason_symbol_string (enum unwind_stop_reason reason)
{
  switch (reason)
    {
#define SET(name, description) \
    case name: return #name;
#include "unwind_stop_reasons.def"
#undef SET

    default:
      internal_error (__FILE__, __LINE__,
		      "Invalid frame stop reason");
    }
}

/* Clean up after a failed (wrong unwinder) attempt to unwind past
   FRAME.  */

void
frame_cleanup_after_sniffer (struct frame_info *frame)
{
  /* The sniffer should not allocate a prologue cache if it did not
     match this frame.  */
  gdb_assert (frame->prologue_cache == NULL);

  /* No sniffer should extend the frame chain; sniff based on what is
     already certain.  */
  gdb_assert (!frame->prev_p);

  /* The sniffer should not check the frame's ID; that's circular.  */
  gdb_assert (frame->this_id.p != frame_id_status::COMPUTED);

  /* Clear cached fields dependent on the unwinder.

     The previous PC is independent of the unwinder, but the previous
     function is not (see get_frame_address_in_block).  */
  frame->prev_func.status = CC_UNKNOWN;
  frame->prev_func.addr = 0;

  /* Discard the unwinder last, so that we can easily find it if an assertion
     in this function triggers.  */
  frame->unwind = NULL;
}

/* Set FRAME's unwinder temporarily, so that we can call a sniffer.
   If sniffing fails, the caller should be sure to call
   frame_cleanup_after_sniffer.  */

void
frame_prepare_for_sniffer (struct frame_info *frame,
			   const struct frame_unwind *unwind)
{
  gdb_assert (frame->unwind == NULL);
  frame->unwind = unwind;
}

static struct cmd_list_element *set_backtrace_cmdlist;
static struct cmd_list_element *show_backtrace_cmdlist;

/* Definition of the "set backtrace" settings that are exposed as
   "backtrace" command options.  */

using boolean_option_def
  = gdb::option::boolean_option_def<set_backtrace_options>;

const gdb::option::option_def set_backtrace_option_defs[] = {

  boolean_option_def {
    "past-main",
    [] (set_backtrace_options *opt) { return &opt->backtrace_past_main; },
    show_backtrace_past_main, /* show_cmd_cb */
    N_("Set whether backtraces should continue past \"main\"."),
    N_("Show whether backtraces should continue past \"main\"."),
    N_("Normally the caller of \"main\" is not of interest, so GDB will terminate\n\
the backtrace at \"main\".  Set this if you need to see the rest\n\
of the stack trace."),
  },

  boolean_option_def {
    "past-entry",
    [] (set_backtrace_options *opt) { return &opt->backtrace_past_entry; },
    show_backtrace_past_entry, /* show_cmd_cb */
    N_("Set whether backtraces should continue past the entry point of a program."),
    N_("Show whether backtraces should continue past the entry point of a program."),
    N_("Normally there are no callers beyond the entry point of a program, so GDB\n\
will terminate the backtrace there.  Set this if you need to see\n\
the rest of the stack trace."),
  },
};

void _initialize_frame ();
void
_initialize_frame ()
{
  obstack_init (&frame_cache_obstack);

  frame_stash_create ();

  gdb::observers::target_changed.attach (frame_observer_target_changed);

  add_basic_prefix_cmd ("backtrace", class_maintenance, _("\
Set backtrace specific variables.\n\
Configure backtrace variables such as the backtrace limit"),
			&set_backtrace_cmdlist, "set backtrace ",
			0/*allow-unknown*/, &setlist);
  add_show_prefix_cmd ("backtrace", class_maintenance, _("\
Show backtrace specific variables.\n\
Show backtrace variables such as the backtrace limit."),
		       &show_backtrace_cmdlist, "show backtrace ",
		       0/*allow-unknown*/, &showlist);

  add_setshow_uinteger_cmd ("limit", class_obscure,
			    &user_set_backtrace_options.backtrace_limit, _("\
Set an upper bound on the number of backtrace levels."), _("\
Show the upper bound on the number of backtrace levels."), _("\
No more than the specified number of frames can be displayed or examined.\n\
Literal \"unlimited\" or zero means no limit."),
			    NULL,
			    show_backtrace_limit,
			    &set_backtrace_cmdlist,
			    &show_backtrace_cmdlist);

  gdb::option::add_setshow_cmds_for_options
    (class_stack, &user_set_backtrace_options,
     set_backtrace_option_defs, &set_backtrace_cmdlist, &show_backtrace_cmdlist);

  /* Debug this files internals.  */
  add_setshow_zuinteger_cmd ("frame", class_maintenance, &frame_debug,  _("\
Set frame debugging."), _("\
Show frame debugging."), _("\
When non-zero, frame specific internal debugging is enabled."),
			     NULL,
			     show_frame_debug,
			     &setdebuglist, &showdebuglist);
}