1 /* GDB/Scheme smobs (gsmob is pronounced "jee smob") 2 3 Copyright (C) 2014-2020 Free Software Foundation, Inc. 4 5 This file is part of GDB. 6 7 This program is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or 10 (at your option) any later version. 11 12 This program is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 19 20 /* See README file in this directory for implementation notes, coding 21 conventions, et.al. */ 22 23 /* Smobs are Guile's "small object". 24 They are used to export C structs to Scheme. 25 26 Note: There's only room in the encoding space for 256, and while we won't 27 come close to that, mixed with other libraries maybe someday we could. 28 We don't worry about it now, except to be aware of the issue. 29 We could allocate just a few smobs and use the unused smob flags field to 30 specify the gdb smob kind, that is left for another day if it ever is 31 needed. 32 33 Some GDB smobs are "chained gsmobs". They are used to assist with life-time 34 tracking of GDB objects vs Scheme objects. Gsmobs can "subclass" 35 chained_gdb_smob, which contains a doubly-linked list to assist with 36 life-time tracking. 37 38 Some other GDB smobs are "eqable gsmobs". Gsmob implementations can 39 "subclass" eqable_gdb_smob to make gsmobs eq?-able. This is done by 40 recording all gsmobs in a hash table and before creating a gsmob first 41 seeing if it's already in the table. Eqable gsmobs can also be used where 42 lifetime-tracking is required. */ 43 44 #include "defs.h" 45 #include "hashtab.h" 46 #include "objfiles.h" 47 #include "guile-internal.h" 48 49 /* We need to call this. Undo our hack to prevent others from calling it. */ 50 #undef scm_make_smob_type 51 52 static htab_t registered_gsmobs; 53 54 /* Hash function for registered_gsmobs hash table. */ 55 56 static hashval_t 57 hash_scm_t_bits (const void *item) 58 { 59 uintptr_t v = (uintptr_t) item; 60 61 return v; 62 } 63 64 /* Equality function for registered_gsmobs hash table. */ 65 66 static int 67 eq_scm_t_bits (const void *item_lhs, const void *item_rhs) 68 { 69 return item_lhs == item_rhs; 70 } 71 72 /* Record GSMOB_CODE as being a gdb smob. 73 GSMOB_CODE is the result of scm_make_smob_type. */ 74 75 static void 76 register_gsmob (scm_t_bits gsmob_code) 77 { 78 void **slot; 79 80 slot = htab_find_slot (registered_gsmobs, (void *) gsmob_code, INSERT); 81 gdb_assert (*slot == NULL); 82 *slot = (void *) gsmob_code; 83 } 84 85 /* Return non-zero if SCM is any registered gdb smob object. */ 86 87 static int 88 gdbscm_is_gsmob (SCM scm) 89 { 90 void **slot; 91 92 if (SCM_IMP (scm)) 93 return 0; 94 slot = htab_find_slot (registered_gsmobs, (void *) SCM_TYP16 (scm), 95 NO_INSERT); 96 return slot != NULL; 97 } 98 99 /* Call this to register a smob, instead of scm_make_smob_type. */ 100 101 scm_t_bits 102 gdbscm_make_smob_type (const char *name, size_t size) 103 { 104 scm_t_bits result = scm_make_smob_type (name, size); 105 106 register_gsmob (result); 107 return result; 108 } 109 110 /* Initialize a gsmob. */ 111 112 void 113 gdbscm_init_gsmob (gdb_smob *base) 114 { 115 base->empty_base_class = 0; 116 } 117 118 /* Initialize a chained_gdb_smob. 119 This is the same as gdbscm_init_gsmob except that it also sets prev,next 120 to NULL. */ 121 122 void 123 gdbscm_init_chained_gsmob (chained_gdb_smob *base) 124 { 125 gdbscm_init_gsmob ((gdb_smob *) base); 126 base->prev = NULL; 127 base->next = NULL; 128 } 129 130 /* Initialize an eqable_gdb_smob. 131 This is the same as gdbscm_init_gsmob except that it also sets 132 BASE->containing_scm to CONTAINING_SCM. */ 133 134 void 135 gdbscm_init_eqable_gsmob (eqable_gdb_smob *base, SCM containing_scm) 136 { 137 gdbscm_init_gsmob ((gdb_smob *) base); 138 base->containing_scm = containing_scm; 139 } 140 141 142 /* gsmob accessors */ 143 144 /* Return the gsmob in SELF. 145 Throws an exception if SELF is not a gsmob. */ 146 147 static SCM 148 gsscm_get_gsmob_arg_unsafe (SCM self, int arg_pos, const char *func_name) 149 { 150 SCM_ASSERT_TYPE (gdbscm_is_gsmob (self), self, arg_pos, func_name, 151 _("any gdb smob")); 152 153 return self; 154 } 155 156 /* (gdb-object-kind gsmob) -> symbol 157 158 Note: While one might want to name this gdb-object-class-name, it is named 159 "-kind" because smobs aren't real GOOPS classes. */ 160 161 static SCM 162 gdbscm_gsmob_kind (SCM self) 163 { 164 SCM smob, result; 165 scm_t_bits smobnum; 166 const char *name; 167 char *kind; 168 169 smob = gsscm_get_gsmob_arg_unsafe (self, SCM_ARG1, FUNC_NAME); 170 171 smobnum = SCM_SMOBNUM (smob); 172 name = SCM_SMOBNAME (smobnum); 173 kind = xstrprintf ("<%s>", name); 174 result = scm_from_latin1_symbol (kind); 175 xfree (kind); 176 177 return result; 178 } 179 180 181 /* When underlying gdb data structures are deleted, we need to update any 182 smobs with references to them. There are several smobs that reference 183 objfile-based data, so we provide helpers to manage this. */ 184 185 /* Add G_SMOB to the reference chain for OBJFILE specified by DATA_KEY. 186 OBJFILE may be NULL, in which case just set prev,next to NULL. */ 187 188 void 189 gdbscm_add_objfile_ref (struct objfile *objfile, 190 const struct objfile_data *data_key, 191 chained_gdb_smob *g_smob) 192 { 193 g_smob->prev = NULL; 194 if (objfile != NULL) 195 { 196 g_smob->next = (chained_gdb_smob *) objfile_data (objfile, data_key); 197 if (g_smob->next) 198 g_smob->next->prev = g_smob; 199 set_objfile_data (objfile, data_key, g_smob); 200 } 201 else 202 g_smob->next = NULL; 203 } 204 205 /* Remove G_SMOB from the reference chain for OBJFILE specified 206 by DATA_KEY. OBJFILE may be NULL. */ 207 208 void 209 gdbscm_remove_objfile_ref (struct objfile *objfile, 210 const struct objfile_data *data_key, 211 chained_gdb_smob *g_smob) 212 { 213 if (g_smob->prev) 214 g_smob->prev->next = g_smob->next; 215 else if (objfile != NULL) 216 set_objfile_data (objfile, data_key, g_smob->next); 217 if (g_smob->next) 218 g_smob->next->prev = g_smob->prev; 219 } 220 221 /* Create a hash table for mapping a pointer to a gdb data structure to the 222 gsmob that wraps it. */ 223 224 htab_t 225 gdbscm_create_eqable_gsmob_ptr_map (htab_hash hash_fn, htab_eq eq_fn) 226 { 227 htab_t htab = htab_create_alloc (7, hash_fn, eq_fn, 228 NULL, xcalloc, xfree); 229 230 return htab; 231 } 232 233 /* Return a pointer to the htab entry for the eq?-able gsmob BASE. 234 If the entry is found, *SLOT is non-NULL. 235 Otherwise *slot is NULL. */ 236 237 eqable_gdb_smob ** 238 gdbscm_find_eqable_gsmob_ptr_slot (htab_t htab, eqable_gdb_smob *base) 239 { 240 void **slot = htab_find_slot (htab, base, INSERT); 241 242 return (eqable_gdb_smob **) slot; 243 } 244 245 /* Record BASE in SLOT. SLOT must be the result of calling 246 gdbscm_find_eqable_gsmob_ptr_slot on BASE (or equivalent for lookup). */ 247 248 void 249 gdbscm_fill_eqable_gsmob_ptr_slot (eqable_gdb_smob **slot, 250 eqable_gdb_smob *base) 251 { 252 *slot = base; 253 } 254 255 /* Remove BASE from HTAB. 256 BASE is a pointer to a gsmob that wraps a pointer to a GDB datum. 257 This is used, for example, when an object is freed. 258 259 It is an error to call this if PTR is not in HTAB (only because it allows 260 for some consistency checking). */ 261 262 void 263 gdbscm_clear_eqable_gsmob_ptr_slot (htab_t htab, eqable_gdb_smob *base) 264 { 265 void **slot = htab_find_slot (htab, base, NO_INSERT); 266 267 gdb_assert (slot != NULL); 268 htab_clear_slot (htab, slot); 269 } 270 271 /* Initialize the Scheme gsmobs code. */ 272 273 static const scheme_function gsmob_functions[] = 274 { 275 /* N.B. There is a general rule of not naming symbols in gdb-guile with a 276 "gdb" prefix. This symbol does not violate this rule because it is to 277 be read as "gdb-object-foo", not "gdb-foo". */ 278 { "gdb-object-kind", 1, 0, 0, as_a_scm_t_subr (gdbscm_gsmob_kind), 279 "\ 280 Return the kind of the GDB object, e.g., <gdb:breakpoint>, as a symbol." }, 281 282 END_FUNCTIONS 283 }; 284 285 void 286 gdbscm_initialize_smobs (void) 287 { 288 registered_gsmobs = htab_create_alloc (10, 289 hash_scm_t_bits, eq_scm_t_bits, 290 NULL, xcalloc, xfree); 291 292 gdbscm_define_functions (gsmob_functions, 1); 293 } 294