| 1 | /* Cleanup routines for GDB, the GNU debugger. |
| 2 | |
| 3 | Copyright (C) 1986-2014 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 | #include "defs.h" |
| 21 | #include "gdb_assert.h" |
| 22 | |
| 23 | /* The cleanup list records things that have to be undone |
| 24 | if an error happens (descriptors to be closed, memory to be freed, etc.) |
| 25 | Each link in the chain records a function to call and an |
| 26 | argument to give it. |
| 27 | |
| 28 | Use make_cleanup to add an element to the cleanup chain. |
| 29 | Use do_cleanups to do all cleanup actions back to a given |
| 30 | point in the chain. Use discard_cleanups to remove cleanups |
| 31 | from the chain back to a given point, not doing them. |
| 32 | |
| 33 | If the argument is pointer to allocated memory, then you need |
| 34 | to additionally set the 'free_arg' member to a function that will |
| 35 | free that memory. This function will be called both when the cleanup |
| 36 | is executed and when it's discarded. */ |
| 37 | |
| 38 | struct cleanup |
| 39 | { |
| 40 | struct cleanup *next; |
| 41 | void (*function) (void *); |
| 42 | void (*free_arg) (void *); |
| 43 | void *arg; |
| 44 | }; |
| 45 | |
| 46 | /* Used to mark the end of a cleanup chain. |
| 47 | The value is chosen so that it: |
| 48 | - is non-NULL so that make_cleanup never returns NULL, |
| 49 | - causes a segv if dereferenced |
| 50 | [though this won't catch errors that a value of, say, |
| 51 | ((struct cleanup *) -1) will] |
| 52 | - displays as something useful when printed in gdb. |
| 53 | This is const for a bit of extra robustness. |
| 54 | It is initialized to coax gcc into putting it into .rodata. |
| 55 | All fields are initialized to survive -Wextra. */ |
| 56 | static const struct cleanup sentinel_cleanup = { 0, 0, 0, 0 }; |
| 57 | |
| 58 | /* Handy macro to use when referring to sentinel_cleanup. */ |
| 59 | #define SENTINEL_CLEANUP ((struct cleanup *) &sentinel_cleanup) |
| 60 | |
| 61 | /* Chain of cleanup actions established with make_cleanup, |
| 62 | to be executed if an error happens. */ |
| 63 | static struct cleanup *cleanup_chain = SENTINEL_CLEANUP; |
| 64 | |
| 65 | /* Chain of cleanup actions established with make_final_cleanup, |
| 66 | to be executed when gdb exits. */ |
| 67 | static struct cleanup *final_cleanup_chain = SENTINEL_CLEANUP; |
| 68 | |
| 69 | /* Main worker routine to create a cleanup. |
| 70 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 71 | FUNCTION is the function to call to perform the cleanup. |
| 72 | ARG is passed to FUNCTION when called. |
| 73 | FREE_ARG, if non-NULL, is called after the cleanup is performed. |
| 74 | |
| 75 | The result is a pointer to the previous chain pointer |
| 76 | to be passed later to do_cleanups or discard_cleanups. */ |
| 77 | |
| 78 | static struct cleanup * |
| 79 | make_my_cleanup2 (struct cleanup **pmy_chain, make_cleanup_ftype *function, |
| 80 | void *arg, void (*free_arg) (void *)) |
| 81 | { |
| 82 | struct cleanup *new |
| 83 | = (struct cleanup *) xmalloc (sizeof (struct cleanup)); |
| 84 | struct cleanup *old_chain = *pmy_chain; |
| 85 | |
| 86 | new->next = *pmy_chain; |
| 87 | new->function = function; |
| 88 | new->free_arg = free_arg; |
| 89 | new->arg = arg; |
| 90 | *pmy_chain = new; |
| 91 | |
| 92 | gdb_assert (old_chain != NULL); |
| 93 | return old_chain; |
| 94 | } |
| 95 | |
| 96 | /* Worker routine to create a cleanup without a destructor. |
| 97 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 98 | FUNCTION is the function to call to perform the cleanup. |
| 99 | ARG is passed to FUNCTION when called. |
| 100 | |
| 101 | The result is a pointer to the previous chain pointer |
| 102 | to be passed later to do_cleanups or discard_cleanups. */ |
| 103 | |
| 104 | static struct cleanup * |
| 105 | make_my_cleanup (struct cleanup **pmy_chain, make_cleanup_ftype *function, |
| 106 | void *arg) |
| 107 | { |
| 108 | return make_my_cleanup2 (pmy_chain, function, arg, NULL); |
| 109 | } |
| 110 | |
| 111 | /* Add a new cleanup to the cleanup_chain, |
| 112 | and return the previous chain pointer |
| 113 | to be passed later to do_cleanups or discard_cleanups. |
| 114 | Args are FUNCTION to clean up with, and ARG to pass to it. */ |
| 115 | |
| 116 | struct cleanup * |
| 117 | make_cleanup (make_cleanup_ftype *function, void *arg) |
| 118 | { |
| 119 | return make_my_cleanup (&cleanup_chain, function, arg); |
| 120 | } |
| 121 | |
| 122 | /* Same as make_cleanup except also includes TDOR, a destructor to free ARG. |
| 123 | DTOR is invoked when the cleanup is performed or when it is discarded. */ |
| 124 | |
| 125 | struct cleanup * |
| 126 | make_cleanup_dtor (make_cleanup_ftype *function, void *arg, |
| 127 | void (*dtor) (void *)) |
| 128 | { |
| 129 | return make_my_cleanup2 (&cleanup_chain, |
| 130 | function, arg, dtor); |
| 131 | } |
| 132 | |
| 133 | /* Same as make_cleanup except the cleanup is added to final_cleanup_chain. */ |
| 134 | |
| 135 | struct cleanup * |
| 136 | make_final_cleanup (make_cleanup_ftype *function, void *arg) |
| 137 | { |
| 138 | return make_my_cleanup (&final_cleanup_chain, function, arg); |
| 139 | } |
| 140 | |
| 141 | /* Worker routine to perform cleanups. |
| 142 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 143 | OLD_CHAIN is the result of a "make" cleanup routine. |
| 144 | Cleanups are performed until we get back to the old end of the chain. */ |
| 145 | |
| 146 | static void |
| 147 | do_my_cleanups (struct cleanup **pmy_chain, |
| 148 | struct cleanup *old_chain) |
| 149 | { |
| 150 | struct cleanup *ptr; |
| 151 | |
| 152 | while ((ptr = *pmy_chain) != old_chain) |
| 153 | { |
| 154 | *pmy_chain = ptr->next; /* Do this first in case of recursion. */ |
| 155 | (*ptr->function) (ptr->arg); |
| 156 | if (ptr->free_arg) |
| 157 | (*ptr->free_arg) (ptr->arg); |
| 158 | xfree (ptr); |
| 159 | } |
| 160 | } |
| 161 | |
| 162 | /* Return a value that can be passed to do_cleanups, do_final_cleanups to |
| 163 | indicate perform all cleanups. */ |
| 164 | |
| 165 | struct cleanup * |
| 166 | all_cleanups (void) |
| 167 | { |
| 168 | return SENTINEL_CLEANUP; |
| 169 | } |
| 170 | |
| 171 | /* Discard cleanups and do the actions they describe |
| 172 | until we get back to the point OLD_CHAIN in the cleanup_chain. */ |
| 173 | |
| 174 | void |
| 175 | do_cleanups (struct cleanup *old_chain) |
| 176 | { |
| 177 | do_my_cleanups (&cleanup_chain, old_chain); |
| 178 | } |
| 179 | |
| 180 | /* Discard cleanups and do the actions they describe |
| 181 | until we get back to the point OLD_CHAIN in the final_cleanup_chain. */ |
| 182 | |
| 183 | void |
| 184 | do_final_cleanups (struct cleanup *old_chain) |
| 185 | { |
| 186 | do_my_cleanups (&final_cleanup_chain, old_chain); |
| 187 | } |
| 188 | |
| 189 | /* Main worker routine to discard cleanups. |
| 190 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 191 | OLD_CHAIN is the result of a "make" cleanup routine. |
| 192 | Cleanups are discarded until we get back to the old end of the chain. */ |
| 193 | |
| 194 | static void |
| 195 | discard_my_cleanups (struct cleanup **pmy_chain, |
| 196 | struct cleanup *old_chain) |
| 197 | { |
| 198 | struct cleanup *ptr; |
| 199 | |
| 200 | while ((ptr = *pmy_chain) != old_chain) |
| 201 | { |
| 202 | *pmy_chain = ptr->next; |
| 203 | if (ptr->free_arg) |
| 204 | (*ptr->free_arg) (ptr->arg); |
| 205 | xfree (ptr); |
| 206 | } |
| 207 | } |
| 208 | |
| 209 | /* Discard cleanups, not doing the actions they describe, |
| 210 | until we get back to the point OLD_CHAIN in the cleanup chain. */ |
| 211 | |
| 212 | void |
| 213 | discard_cleanups (struct cleanup *old_chain) |
| 214 | { |
| 215 | discard_my_cleanups (&cleanup_chain, old_chain); |
| 216 | } |
| 217 | |
| 218 | /* Discard final cleanups, not doing the actions they describe, |
| 219 | until we get back to the point OLD_CHAIN in the final cleanup chain. */ |
| 220 | |
| 221 | void |
| 222 | discard_final_cleanups (struct cleanup *old_chain) |
| 223 | { |
| 224 | discard_my_cleanups (&final_cleanup_chain, old_chain); |
| 225 | } |
| 226 | |
| 227 | /* Main worker routine to save cleanups. |
| 228 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 229 | The chain is emptied and the result is a pointer to the old chain. */ |
| 230 | |
| 231 | static struct cleanup * |
| 232 | save_my_cleanups (struct cleanup **pmy_chain) |
| 233 | { |
| 234 | struct cleanup *old_chain = *pmy_chain; |
| 235 | |
| 236 | *pmy_chain = SENTINEL_CLEANUP; |
| 237 | return old_chain; |
| 238 | } |
| 239 | |
| 240 | /* Set the cleanup_chain to 0, and return the old cleanup_chain. */ |
| 241 | |
| 242 | struct cleanup * |
| 243 | save_cleanups (void) |
| 244 | { |
| 245 | return save_my_cleanups (&cleanup_chain); |
| 246 | } |
| 247 | |
| 248 | /* Set the final_cleanup_chain to 0, and return the old |
| 249 | final_cleanup_chain. */ |
| 250 | |
| 251 | struct cleanup * |
| 252 | save_final_cleanups (void) |
| 253 | { |
| 254 | return save_my_cleanups (&final_cleanup_chain); |
| 255 | } |
| 256 | |
| 257 | /* Main worker routine to save cleanups. |
| 258 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 259 | The chain is restored from CHAIN. */ |
| 260 | |
| 261 | static void |
| 262 | restore_my_cleanups (struct cleanup **pmy_chain, struct cleanup *chain) |
| 263 | { |
| 264 | if (*pmy_chain != SENTINEL_CLEANUP) |
| 265 | internal_warning (__FILE__, __LINE__, |
| 266 | _("restore_my_cleanups has found a stale cleanup")); |
| 267 | |
| 268 | *pmy_chain = chain; |
| 269 | } |
| 270 | |
| 271 | /* Restore the cleanup chain from a previously saved chain. */ |
| 272 | |
| 273 | void |
| 274 | restore_cleanups (struct cleanup *chain) |
| 275 | { |
| 276 | restore_my_cleanups (&cleanup_chain, chain); |
| 277 | } |
| 278 | |
| 279 | /* Restore the final cleanup chain from a previously saved chain. */ |
| 280 | |
| 281 | void |
| 282 | restore_final_cleanups (struct cleanup *chain) |
| 283 | { |
| 284 | restore_my_cleanups (&final_cleanup_chain, chain); |
| 285 | } |
| 286 | |
| 287 | /* Provide a known function that does nothing, to use as a base for |
| 288 | a possibly long chain of cleanups. This is useful where we |
| 289 | use the cleanup chain for handling normal cleanups as well as dealing |
| 290 | with cleanups that need to be done as a result of a call to error(). |
| 291 | In such cases, we may not be certain where the first cleanup is, unless |
| 292 | we have a do-nothing one to always use as the base. */ |
| 293 | |
| 294 | void |
| 295 | null_cleanup (void *arg) |
| 296 | { |
| 297 | } |