| 1 | /* Cleanup routines for GDB, the GNU debugger. |
| 2 | |
| 3 | Copyright (C) 1986-2019 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 "common-defs.h" |
| 21 | #include "cleanups.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_final_cleanup, |
| 62 | to be executed when gdb exits. */ |
| 63 | static struct cleanup *final_cleanup_chain = SENTINEL_CLEANUP; |
| 64 | |
| 65 | /* Main worker routine to create a cleanup. |
| 66 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 67 | FUNCTION is the function to call to perform the cleanup. |
| 68 | ARG is passed to FUNCTION when called. |
| 69 | FREE_ARG, if non-NULL, is called after the cleanup is performed. |
| 70 | |
| 71 | The result is a pointer to the previous chain pointer |
| 72 | to be passed later to do_cleanups or discard_cleanups. */ |
| 73 | |
| 74 | static struct cleanup * |
| 75 | make_my_cleanup2 (struct cleanup **pmy_chain, make_cleanup_ftype *function, |
| 76 | void *arg, void (*free_arg) (void *)) |
| 77 | { |
| 78 | struct cleanup *newobj = XNEW (struct cleanup); |
| 79 | struct cleanup *old_chain = *pmy_chain; |
| 80 | |
| 81 | newobj->next = *pmy_chain; |
| 82 | newobj->function = function; |
| 83 | newobj->free_arg = free_arg; |
| 84 | newobj->arg = arg; |
| 85 | *pmy_chain = newobj; |
| 86 | |
| 87 | gdb_assert (old_chain != NULL); |
| 88 | return old_chain; |
| 89 | } |
| 90 | |
| 91 | /* Worker routine to create a cleanup without a destructor. |
| 92 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 93 | FUNCTION is the function to call to perform the cleanup. |
| 94 | ARG is passed to FUNCTION when called. |
| 95 | |
| 96 | The result is a pointer to the previous chain pointer |
| 97 | to be passed later to do_cleanups or discard_cleanups. */ |
| 98 | |
| 99 | static struct cleanup * |
| 100 | make_my_cleanup (struct cleanup **pmy_chain, make_cleanup_ftype *function, |
| 101 | void *arg) |
| 102 | { |
| 103 | return make_my_cleanup2 (pmy_chain, function, arg, NULL); |
| 104 | } |
| 105 | |
| 106 | /* Add a new cleanup to the final cleanup_chain, |
| 107 | and return the previous chain pointer |
| 108 | to be passed later to do_cleanups or discard_cleanups. |
| 109 | Args are FUNCTION to clean up with, and ARG to pass to it. */ |
| 110 | |
| 111 | struct cleanup * |
| 112 | make_final_cleanup (make_cleanup_ftype *function, void *arg) |
| 113 | { |
| 114 | return make_my_cleanup (&final_cleanup_chain, function, arg); |
| 115 | } |
| 116 | |
| 117 | /* Worker routine to perform cleanups. |
| 118 | PMY_CHAIN is a pointer to either cleanup_chain or final_cleanup_chain. |
| 119 | OLD_CHAIN is the result of a "make" cleanup routine. |
| 120 | Cleanups are performed until we get back to the old end of the chain. */ |
| 121 | |
| 122 | static void |
| 123 | do_my_cleanups (struct cleanup **pmy_chain, |
| 124 | struct cleanup *old_chain) |
| 125 | { |
| 126 | struct cleanup *ptr; |
| 127 | |
| 128 | while ((ptr = *pmy_chain) != old_chain) |
| 129 | { |
| 130 | *pmy_chain = ptr->next; /* Do this first in case of recursion. */ |
| 131 | (*ptr->function) (ptr->arg); |
| 132 | if (ptr->free_arg) |
| 133 | (*ptr->free_arg) (ptr->arg); |
| 134 | xfree (ptr); |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | /* Discard final cleanups and do the actions they describe. */ |
| 139 | |
| 140 | void |
| 141 | do_final_cleanups () |
| 142 | { |
| 143 | do_my_cleanups (&final_cleanup_chain, SENTINEL_CLEANUP); |
| 144 | } |