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gnu-v2-abi.c
Go to the documentation of this file.
1/* Abstraction of GNU v2 abi.
2
3 Copyright (C) 2001-2023 Free Software Foundation, Inc.
4
5 Contributed by Daniel Berlin <dberlin@redhat.com>
6
7 This file is part of GDB.
8
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3 of the License, or
12 (at your option) any later version.
13
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with this program. If not, see <http://www.gnu.org/licenses/>. */
21
22#include "defs.h"
23#include "symtab.h"
24#include "gdbtypes.h"
25#include "value.h"
26#include "demangle.h"
27#include "gdb-demangle.h"
28#include "cp-abi.h"
29#include "cp-support.h"
30#include <ctype.h>
31
33
34static int vb_match (struct type *, int, struct type *);
35
36static enum dtor_kinds
38{
39 if ((name[0] == '_' && is_cplus_marker (name[1]) && name[2] == '_')
40 || startswith (name, "__dt__"))
42 else
43 return (enum dtor_kinds) 0;
44}
45
46static enum ctor_kinds
48{
49 if ((name[0] == '_' && name[1] == '_'
50 && (isdigit (name[2]) || strchr ("Qt", name[2])))
51 || startswith (name, "__ct__"))
53 else
54 return (enum ctor_kinds) 0;
55}
56
57static int
59{
60 return (((name)[0] == '_'
61 && (((name)[1] == 'V' && (name)[2] == 'T')
62 || ((name)[1] == 'v' && (name)[2] == 't'))
63 && is_cplus_marker ((name)[3])) ||
64 ((name)[0] == '_' && (name)[1] == '_'
65 && (name)[2] == 'v' && (name)[3] == 't' && (name)[4] == '_'));
66}
67
68static int
70{
71 return startswith (name, CP_OPERATOR_STR);
72}
73
74
75/* Return a virtual function as a value.
76 ARG1 is the object which provides the virtual function
77 table pointer. *ARG1P is side-effected in calling this function.
78 F is the list of member functions which contains the desired virtual
79 function.
80 J is an index into F which provides the desired virtual function.
81
82 TYPE is the type in which F is located. */
83static struct value *
84gnuv2_virtual_fn_field (struct value **arg1p, struct fn_field * f, int j,
85 struct type * type, int offset)
86{
87 struct value *arg1 = *arg1p;
88 struct type *type1 = check_typedef (arg1->type ());
89 struct type *entry_type;
90 /* First, get the virtual function table pointer. That comes
91 with a strange type, so cast it to type `pointer to long' (which
92 should serve just fine as a function type). Then, index into
93 the table, and convert final value to appropriate function type. */
94 struct value *entry;
95 struct value *vfn;
96 struct value *vtbl;
97 LONGEST vi = (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j);
98 struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
99 struct type *context;
100 struct type *context_vptr_basetype;
101 int context_vptr_fieldno;
102
103 if (fcontext == NULL)
104 /* We don't have an fcontext (e.g. the program was compiled with
105 g++ version 1). Try to get the vtbl from the TYPE_VPTR_BASETYPE.
106 This won't work right for multiple inheritance, but at least we
107 should do as well as GDB 3.x did. */
108 fcontext = TYPE_VPTR_BASETYPE (type);
109 context = lookup_pointer_type (fcontext);
110 /* Now context is a pointer to the basetype containing the vtbl. */
111 if (context->target_type () != type1)
112 {
113 struct value *tmp = value_cast (context, value_addr (arg1));
114
115 arg1 = value_ind (tmp);
116 type1 = check_typedef (arg1->type ());
117 }
118
119 context = type1;
120 /* Now context is the basetype containing the vtbl. */
121
122 /* This type may have been defined before its virtual function table
123 was. If so, fill in the virtual function table entry for the
124 type now. */
125 context_vptr_fieldno = get_vptr_fieldno (context, &context_vptr_basetype);
126 /* FIXME: What to do if vptr_fieldno is still -1? */
127
128 /* The virtual function table is now an array of structures
129 which have the form { int16 offset, delta; void *pfn; }. */
130 vtbl = arg1->primitive_field (0, context_vptr_fieldno,
131 context_vptr_basetype);
132
133 /* With older versions of g++, the vtbl field pointed to an array
134 of structures. Nowadays it points directly to the structure. */
135 if (vtbl->type ()->code () == TYPE_CODE_PTR
136 && vtbl->type ()->target_type ()->code () == TYPE_CODE_ARRAY)
137 {
138 /* Handle the case where the vtbl field points to an
139 array of structures. */
140 vtbl = value_ind (vtbl);
141
142 /* Index into the virtual function table. This is hard-coded because
143 looking up a field is not cheap, and it may be important to save
144 time, e.g. if the user has set a conditional breakpoint calling
145 a virtual function. */
146 entry = value_subscript (vtbl, vi);
147 }
148 else
149 {
150 /* Handle the case where the vtbl field points directly to a
151 structure. */
152 vtbl = value_ptradd (vtbl, vi);
153 entry = value_ind (vtbl);
154 }
155
156 entry_type = check_typedef (entry->type ());
157
158 if (entry_type->code () == TYPE_CODE_STRUCT)
159 {
160 /* Move the `this' pointer according to the virtual function table. */
161 arg1->set_offset (arg1->offset ()
162 + value_as_long (value_field (entry, 0)));
163
164 if (!arg1->lazy ())
165 {
166 arg1->set_lazy (true);
167 arg1->fetch_lazy ();
168 }
169
170 vfn = value_field (entry, 2);
171 }
172 else if (entry_type->code () == TYPE_CODE_PTR)
173 vfn = entry;
174 else
175 error (_("I'm confused: virtual function table has bad type"));
176 /* Reinstantiate the function pointer with the correct type. */
178
179 *arg1p = arg1;
180 return vfn;
181}
182
183
184static struct type *
185gnuv2_value_rtti_type (struct value *v, int *full, LONGEST *top, int *using_enc)
186{
187 struct type *known_type;
188 struct type *rtti_type;
189 CORE_ADDR vtbl;
191 char *p;
192 const char *linkage_name;
193 struct type *btype;
194 struct type *known_type_vptr_basetype;
195 int known_type_vptr_fieldno;
196
197 if (full)
198 *full = 0;
199 if (top)
200 *top = -1;
201 if (using_enc)
202 *using_enc = 0;
203
204 /* Get declared type. */
205 known_type = v->type ();
206 known_type = check_typedef (known_type);
207 /* RTTI works only or class objects. */
208 if (known_type->code () != TYPE_CODE_STRUCT)
209 return NULL;
210
211 /* Plan on this changing in the future as i get around to setting
212 the vtables properly for G++ compiled stuff. Also, I'll be using
213 the type info functions, which are always right. Deal with it
214 until then. */
215
216 /* Try to get the vptr basetype, fieldno. */
217 known_type_vptr_fieldno = get_vptr_fieldno (known_type,
218 &known_type_vptr_basetype);
219
220 /* If we can't find it, give up. */
221 if (known_type_vptr_fieldno < 0)
222 return NULL;
223
224 /* Make sure our basetype and known type match, otherwise, cast
225 so we can get at the vtable properly. */
226 btype = known_type_vptr_basetype;
227 btype = check_typedef (btype);
228 if (btype != known_type )
229 {
230 v = value_cast (btype, v);
231 if (using_enc)
232 *using_enc=1;
233 }
234 /* We can't use value_ind here, because it would want to use RTTI, and
235 we'd waste a bunch of time figuring out we already know the type.
236 Besides, we don't care about the type, just the actual pointer. */
237 if (value_field (v, known_type_vptr_fieldno)->address () == 0)
238 return NULL;
239
240 vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
241
242 /* Try to find a symbol that is the vtable. */
243 minsym=lookup_minimal_symbol_by_pc(vtbl);
244 if (minsym.minsym==NULL
245 || (linkage_name=minsym.minsym->linkage_name ())==NULL
246 || !is_vtable_name (linkage_name))
247 return NULL;
248
249 /* If we just skip the prefix, we get screwed by namespaces. */
250 gdb::unique_xmalloc_ptr<char> demangled_name
251 = gdb_demangle(linkage_name,DMGL_PARAMS|DMGL_ANSI);
252 p = strchr (demangled_name.get (), ' ');
253 if (p)
254 *p = '\0';
255
256 /* Lookup the type for the name. */
257 /* FIXME: chastain/2003-11-26: block=NULL is bogus. See pr gdb/1465. */
258 rtti_type = cp_lookup_rtti_type (demangled_name.get (), NULL);
259 if (rtti_type == NULL)
260 return NULL;
261
262 if (TYPE_N_BASECLASSES(rtti_type) > 1 && full && (*full) != 1)
263 {
264 if (top)
265 *top = TYPE_BASECLASS_BITPOS (rtti_type,
266 TYPE_VPTR_FIELDNO(rtti_type)) / 8;
267 if (top && ((*top) >0))
268 {
269 if (rtti_type->length () > known_type->length ())
270 {
271 if (full)
272 *full=0;
273 }
274 else
275 {
276 if (full)
277 *full=1;
278 }
279 }
280 }
281 else
282 {
283 if (full)
284 *full=1;
285 }
286
287 return rtti_type;
288}
289
290/* Return true if the INDEXth field of TYPE is a virtual baseclass
291 pointer which is for the base class whose type is BASECLASS. */
292
293static int
294vb_match (struct type *type, int index, struct type *basetype)
295{
296 struct type *fieldtype;
297 const char *name = type->field (index).name ();
298 const char *field_class_name = NULL;
299
300 if (*name != '_')
301 return 0;
302 /* gcc 2.4 uses _vb$. */
303 if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
304 field_class_name = name + 4;
305 /* gcc 2.5 will use __vb_. */
306 if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
307 field_class_name = name + 5;
308
309 if (field_class_name == NULL)
310 /* This field is not a virtual base class pointer. */
311 return 0;
312
313 /* It's a virtual baseclass pointer, now we just need to find out whether
314 it is for this baseclass. */
315 fieldtype = type->field (index).type ();
316 if (fieldtype == NULL
317 || fieldtype->code () != TYPE_CODE_PTR)
318 /* "Can't happen". */
319 return 0;
320
321 /* What we check for is that either the types are equal (needed for
322 nameless types) or have the same name. This is ugly, and a more
323 elegant solution should be devised (which would probably just push
324 the ugliness into symbol reading unless we change the stabs format). */
325 if (fieldtype->target_type () == basetype)
326 return 1;
327
328 if (basetype->name () != NULL
329 && fieldtype->target_type ()->name () != NULL
330 && strcmp (basetype->name (),
331 fieldtype->target_type ()->name ()) == 0)
332 return 1;
333 return 0;
334}
335
336/* Compute the offset of the baseclass which is the INDEXth baseclass
337 of class TYPE, for value at VALADDR (in host) at ADDRESS (in
338 target). The result is the offset of the baseclass value relative
339 to (the address of)(ARG) + OFFSET. */
340
341static int
342gnuv2_baseclass_offset (struct type *type, int index,
343 const bfd_byte *valaddr, LONGEST embedded_offset,
344 CORE_ADDR address, const struct value *val)
345{
346 struct type *basetype = TYPE_BASECLASS (type, index);
347
348 if (BASETYPE_VIA_VIRTUAL (type, index))
349 {
350 /* Must hunt for the pointer to this virtual baseclass. */
351 int i, len = type->num_fields ();
352 int n_baseclasses = TYPE_N_BASECLASSES (type);
353
354 /* First look for the virtual baseclass pointer
355 in the fields. */
356 for (i = n_baseclasses; i < len; i++)
357 {
358 if (vb_match (type, i, basetype))
359 {
360 struct type *field_type;
361 LONGEST field_offset;
362 int field_length;
363 CORE_ADDR addr;
364
365 field_type = check_typedef (type->field (i).type ());
366 field_offset = type->field (i).loc_bitpos () / 8;
367 field_length = field_type->length ();
368
369 if (!val->bytes_available (embedded_offset + field_offset,
370 field_length))
371 throw_error (NOT_AVAILABLE_ERROR,
372 _("Virtual baseclass pointer is not available"));
373
374 addr = unpack_pointer (field_type,
375 valaddr + embedded_offset + field_offset);
376
377 return addr - (LONGEST) address + embedded_offset;
378 }
379 }
380 /* Not in the fields, so try looking through the baseclasses. */
381 for (i = index + 1; i < n_baseclasses; i++)
382 {
383 /* Don't go through baseclass_offset, as that wraps
384 exceptions, thus, inner exceptions would be wrapped more
385 than once. */
386 int boffset =
387 gnuv2_baseclass_offset (type, i, valaddr,
388 embedded_offset, address, val);
389
390 if (boffset)
391 return boffset;
392 }
393
394 error (_("Baseclass offset not found"));
395 }
396
397 /* Baseclass is easily computed. */
398 return TYPE_BASECLASS_BITPOS (type, index) / 8;
399}
400
401static void
415
417void
const char *const name
void f()
Definition 1.cc:36
int register_cp_abi(struct cp_abi_ops *abi)
Definition cp-abi.c:252
int is_vtable_name(const char *name)
Definition cp-abi.c:53
dtor_kinds
Definition cp-abi.h:61
@ complete_object_dtor
Definition cp-abi.h:69
ctor_kinds
Definition cp-abi.h:40
@ complete_object_ctor
Definition cp-abi.h:44
gdb::unique_xmalloc_ptr< char > gdb_demangle(const char *name, int options)
struct type * cp_lookup_rtti_type(const char *name, const struct block *block)
#define CP_OPERATOR_STR
Definition cp-support.h:51
bool is_cplus_marker(int c)
struct type * lookup_pointer_type(struct type *type)
Definition gdbtypes.c:430
int get_vptr_fieldno(struct type *type, struct type **basetypep)
Definition gdbtypes.c:1977
struct type * check_typedef(struct type *type)
Definition gdbtypes.c:2966
#define TYPE_VPTR_BASETYPE(thistype)
Definition gdbtypes.h:1923
#define TYPE_FN_FIELD_VOFFSET(thisfn, n)
Definition gdbtypes.h:2012
#define TYPE_FN_FIELD_TYPE(thisfn, n)
Definition gdbtypes.h:2002
#define TYPE_BASECLASS(thistype, index)
Definition gdbtypes.h:1946
#define TYPE_BASECLASS_BITPOS(thistype, index)
Definition gdbtypes.h:1949
#define TYPE_VPTR_FIELDNO(thistype)
Definition gdbtypes.h:1922
#define BASETYPE_VIA_VIRTUAL(thistype, index)
Definition gdbtypes.h:1954
#define TYPE_N_BASECLASSES(thistype)
Definition gdbtypes.h:1947
#define TYPE_FN_FIELD_FCONTEXT(thisfn, n)
Definition gdbtypes.h:2011
void _initialize_gnu_v2_abi()
Definition gnu-v2-abi.c:418
static int gnuv2_is_operator_name(const char *name)
Definition gnu-v2-abi.c:69
static enum ctor_kinds gnuv2_is_constructor_name(const char *name)
Definition gnu-v2-abi.c:47
static struct type * gnuv2_value_rtti_type(struct value *v, int *full, LONGEST *top, int *using_enc)
Definition gnu-v2-abi.c:185
static enum dtor_kinds gnuv2_is_destructor_name(const char *name)
Definition gnu-v2-abi.c:37
static struct value * gnuv2_virtual_fn_field(struct value **arg1p, struct fn_field *f, int j, struct type *type, int offset)
Definition gnu-v2-abi.c:84
static int gnuv2_is_vtable_name(const char *name)
Definition gnu-v2-abi.c:58
static cp_abi_ops gnu_v2_abi_ops
Definition gnu-v2-abi.c:32
static int vb_match(struct type *, int, struct type *)
Definition gnu-v2-abi.c:294
static int gnuv2_baseclass_offset(struct type *type, int index, const bfd_byte *valaddr, LONGEST embedded_offset, CORE_ADDR address, const struct value *val)
Definition gnu-v2-abi.c:342
static void init_gnuv2_ops(void)
Definition gnu-v2-abi.c:402
struct bound_minimal_symbol lookup_minimal_symbol_by_pc(CORE_ADDR pc)
Definition minsyms.c:996
struct minimal_symbol * minsym
Definition minsyms.h:49
const char * shortname
Definition cp-abi.h:218
int(* baseclass_offset)(struct type *type, int index, const bfd_byte *valaddr, LONGEST embedded_offset, CORE_ADDR address, const struct value *val)
Definition cp-abi.h:234
int(* is_vtable_name)(const char *name)
Definition cp-abi.h:226
enum ctor_kinds(* is_constructor_name)(const char *name)
Definition cp-abi.h:224
struct value *(* virtual_fn_field)(struct value **arg1p, struct fn_field *f, int j, struct type *type, int offset)
Definition cp-abi.h:228
enum dtor_kinds(* is_destructor_name)(const char *name)
Definition cp-abi.h:225
int(* is_operator_name)(const char *name)
Definition cp-abi.h:227
const char * longname
Definition cp-abi.h:219
const char * doc
Definition cp-abi.h:220
struct type *(* rtti_type)(struct value *v, int *full, LONGEST *top, int *using_enc)
Definition cp-abi.h:232
LONGEST loc_bitpos() const
Definition gdbtypes.h:611
const char * name() const
Definition gdbtypes.h:557
struct type * type() const
Definition gdbtypes.h:547
const char * linkage_name() const
Definition symtab.h:460
struct type * target_type() const
Definition gdbtypes.h:1037
type_code code() const
Definition gdbtypes.h:956
ULONGEST length() const
Definition gdbtypes.h:983
struct field & field(int idx) const
Definition gdbtypes.h:1012
unsigned int num_fields() const
Definition gdbtypes.h:994
const char * name() const
Definition gdbtypes.h:968
Definition value.h:130
struct value * primitive_field(LONGEST offset, int fieldno, struct type *arg_type)
Definition value.c:2932
bool lazy() const
Definition value.h:265
bool bytes_available(LONGEST offset, ULONGEST length) const
Definition value.c:187
void set_lazy(bool val)
Definition value.h:268
struct type * type() const
Definition value.h:180
void set_offset(LONGEST offset)
Definition value.h:225
LONGEST offset() const
Definition value.h:222
void fetch_lazy()
Definition value.c:4001
void deprecated_set_type(struct type *type)
Definition value.h:186
struct value * value_subscript(struct value *array, LONGEST index)
Definition valarith.c:141
struct value * value_ptradd(struct value *arg1, LONGEST arg2)
Definition valarith.c:79
struct value * value_addr(struct value *arg1)
Definition valops.c:1551
struct value * value_cast(struct type *type, struct value *arg2)
Definition valops.c:403
struct value * value_ind(struct value *arg1)
Definition valops.c:1630
struct value * value_field(struct value *arg1, int fieldno)
Definition value.c:3052
CORE_ADDR unpack_pointer(struct type *type, const gdb_byte *valaddr)
Definition value.c:2843
CORE_ADDR value_as_address(struct value *val)
Definition value.c:2636
LONGEST value_as_long(struct value *val)
Definition value.c:2554