gdb/guile/scm-gsmob.c

   1 /* GDB/Scheme smobs (gsmob is pronounced "jee smob")
   2
   3    Copyright (C) 2014-2022 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    Exports the created smob type from the current module.  */
 101
 102 scm_t_bits
 103 gdbscm_make_smob_type (const char *name, size_t size)
 104 {
 105   scm_t_bits result = scm_make_smob_type (name, size);
 106
 107   register_gsmob (result);
 108
 109 #if SCM_MAJOR_VERSION == 2 && SCM_MINOR_VERSION == 0
 110   /* Prior to Guile 2.1.0, smob classes were only exposed via exports
 111      from the (oop goops) module.  */
 112   SCM bound_name = scm_string_append (scm_list_3 (scm_from_latin1_string ("<"),
 113                                                   scm_from_latin1_string (name),
 114                                                   scm_from_latin1_string (">")));
 115   bound_name = scm_string_to_symbol (bound_name);
 116   SCM smob_type = scm_public_ref (scm_list_2 (scm_from_latin1_symbol ("oop"),
 117                                               scm_from_latin1_symbol ("goops")),
 118                                   bound_name);
 119 #elif SCM_MAJOR_VERSION == 2 && SCM_MINOR_VERSION == 1 && SCM_MICRO_VERSION == 0
 120   /* Guile 2.1.0 doesn't provide any API for looking up smob classes.
 121      We could try allocating a fake instance and using scm_class_of,
 122      but it's probably not worth the trouble for the sake of a single
 123      development release.  */
 124 #  error "Unsupported Guile version"
 125 #else
 126   /* Guile 2.1.1 and above provides scm_smob_type_class.  */
 127   SCM smob_type = scm_smob_type_class (result);
 128 #endif
 129
 130   SCM smob_type_name = scm_class_name (smob_type);
 131   scm_define (smob_type_name, smob_type);
 132   scm_module_export (scm_current_module (), scm_list_1 (smob_type_name));
 133
 134   return result;
 135 }
 136
 137 /* Initialize a gsmob.  */
 138
 139 void
 140 gdbscm_init_gsmob (gdb_smob *base)
 141 {
 142   base->empty_base_class = 0;
 143 }
 144
 145 /* Initialize a chained_gdb_smob.
 146    This is the same as gdbscm_init_gsmob except that it also sets prev,next
 147    to NULL.  */
 148
 149 void
 150 gdbscm_init_chained_gsmob (chained_gdb_smob *base)
 151 {
 152   gdbscm_init_gsmob ((gdb_smob *) base);
 153   base->prev = NULL;
 154   base->next = NULL;
 155 }
 156
 157 /* Initialize an eqable_gdb_smob.
 158    This is the same as gdbscm_init_gsmob except that it also sets
 159    BASE->containing_scm to CONTAINING_SCM.  */
 160
 161 void
 162 gdbscm_init_eqable_gsmob (eqable_gdb_smob *base, SCM containing_scm)
 163 {
 164   gdbscm_init_gsmob ((gdb_smob *) base);
 165   base->containing_scm = containing_scm;
 166 }
 167
 168 \f
 169 /* gsmob accessors */
 170
 171 /* Return the gsmob in SELF.
 172    Throws an exception if SELF is not a gsmob.  */
 173
 174 static SCM
 175 gsscm_get_gsmob_arg_unsafe (SCM self, int arg_pos, const char *func_name)
 176 {
 177   SCM_ASSERT_TYPE (gdbscm_is_gsmob (self), self, arg_pos, func_name,
 178                    _("any gdb smob"));
 179
 180   return self;
 181 }
 182
 183 /* (gdb-object-kind gsmob) -> symbol
 184
 185    Note: While one might want to name this gdb-object-class-name, it is named
 186    "-kind" because smobs aren't real GOOPS classes.  */
 187
 188 static SCM
 189 gdbscm_gsmob_kind (SCM self)
 190 {
 191   SCM smob, result;
 192   scm_t_bits smobnum;
 193   const char *name;
 194
 195   smob = gsscm_get_gsmob_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
 196
 197   smobnum = SCM_SMOBNUM (smob);
 198   name = SCM_SMOBNAME (smobnum);
 199   gdb::unique_xmalloc_ptr<char> kind = xstrprintf ("<%s>", name);
 200   result = scm_from_latin1_symbol (kind.get ());
 201   return result;
 202 }
 203
 204 \f
 205 /* When underlying gdb data structures are deleted, we need to update any
 206    smobs with references to them.  There are several smobs that reference
 207    objfile-based data, so we provide helpers to manage this.  */
 208
 209 /* Create a hash table for mapping a pointer to a gdb data structure to the
 210    gsmob that wraps it.  */
 211
 212 htab_t
 213 gdbscm_create_eqable_gsmob_ptr_map (htab_hash hash_fn, htab_eq eq_fn)
 214 {
 215   htab_t htab = htab_create_alloc (7, hash_fn, eq_fn,
 216                                    NULL, xcalloc, xfree);
 217
 218   return htab;
 219 }
 220
 221 /* Return a pointer to the htab entry for the eq?-able gsmob BASE.
 222    If the entry is found, *SLOT is non-NULL.
 223    Otherwise *slot is NULL.  */
 224
 225 eqable_gdb_smob **
 226 gdbscm_find_eqable_gsmob_ptr_slot (htab_t htab, eqable_gdb_smob *base)
 227 {
 228   void **slot = htab_find_slot (htab, base, INSERT);
 229
 230   return (eqable_gdb_smob **) slot;
 231 }
 232
 233 /* Record BASE in SLOT.  SLOT must be the result of calling
 234    gdbscm_find_eqable_gsmob_ptr_slot on BASE (or equivalent for lookup).  */
 235
 236 void
 237 gdbscm_fill_eqable_gsmob_ptr_slot (eqable_gdb_smob **slot,
 238                                    eqable_gdb_smob *base)
 239 {
 240   *slot = base;
 241 }
 242
 243 /* Remove BASE from HTAB.
 244    BASE is a pointer to a gsmob that wraps a pointer to a GDB datum.
 245    This is used, for example, when an object is freed.
 246
 247    It is an error to call this if PTR is not in HTAB (only because it allows
 248    for some consistency checking).  */
 249
 250 void
 251 gdbscm_clear_eqable_gsmob_ptr_slot (htab_t htab, eqable_gdb_smob *base)
 252 {
 253   void **slot = htab_find_slot (htab, base, NO_INSERT);
 254
 255   gdb_assert (slot != NULL);
 256   htab_clear_slot (htab, slot);
 257 }
 258 \f
 259 /* Initialize the Scheme gsmobs code.  */
 260
 261 static const scheme_function gsmob_functions[] =
 262 {
 263   /* N.B. There is a general rule of not naming symbols in gdb-guile with a
 264      "gdb" prefix.  This symbol does not violate this rule because it is to
 265      be read as "gdb-object-foo", not "gdb-foo".  */
 266   { "gdb-object-kind", 1, 0, 0, as_a_scm_t_subr (gdbscm_gsmob_kind),
 267     "\
 268 Return the kind of the GDB object, e.g., <gdb:breakpoint>, as a symbol." },
 269
 270   END_FUNCTIONS
 271 };
 272
 273 void
 274 gdbscm_initialize_smobs (void)
 275 {
 276   registered_gsmobs = htab_create_alloc (10,
 277                                          hash_scm_t_bits, eq_scm_t_bits,
 278                                          NULL, xcalloc, xfree);
 279
 280   gdbscm_define_functions (gsmob_functions, 1);
 281 }