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3185942a JA |
1 | /* unwind_prot.c - a simple unwind-protect system for internal variables */ |
2 | ||
726f6388 JA |
3 | /* I can't stand it anymore! Please can't we just write the |
4 | whole Unix system in lisp or something? */ | |
5 | ||
3185942a | 6 | /* Copyright (C) 1987-2009 Free Software Foundation, Inc. |
726f6388 | 7 | |
3185942a | 8 | This file is part of GNU Bash, the Bourne Again SHell. |
726f6388 | 9 | |
3185942a JA |
10 | Bash is free software: you can redistribute it and/or modify |
11 | it under the terms of the GNU General Public License as published by | |
12 | the Free Software Foundation, either version 3 of the License, or | |
13 | (at your option) any later version. | |
726f6388 | 14 | |
3185942a JA |
15 | Bash is distributed in the hope that it will be useful, |
16 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | GNU General Public License for more details. | |
726f6388 | 19 | |
3185942a JA |
20 | You should have received a copy of the GNU General Public License |
21 | along with Bash. If not, see <http://www.gnu.org/licenses/>. | |
22 | */ | |
726f6388 JA |
23 | |
24 | /* **************************************************************** */ | |
25 | /* */ | |
26 | /* Unwind Protection Scheme for Bash */ | |
27 | /* */ | |
28 | /* **************************************************************** */ | |
726f6388 | 29 | #include "config.h" |
ccc6cda3 JA |
30 | |
31 | #include "bashtypes.h" | |
d166f048 JA |
32 | #include "bashansi.h" |
33 | ||
ccc6cda3 JA |
34 | #if defined (HAVE_UNISTD_H) |
35 | # include <unistd.h> | |
36 | #endif | |
37 | ||
f73dda09 JA |
38 | #if STDC_HEADERS |
39 | # include <stddef.h> | |
40 | #endif | |
41 | ||
42 | #ifndef offsetof | |
43 | # define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) | |
44 | #endif | |
45 | ||
726f6388 JA |
46 | #include "command.h" |
47 | #include "general.h" | |
48 | #include "unwind_prot.h" | |
49 | #include "quit.h" | |
ccc6cda3 | 50 | #include "sig.h" |
726f6388 | 51 | |
f73dda09 | 52 | /* Structure describing a saved variable and the value to restore it to. */ |
d166f048 | 53 | typedef struct { |
f73dda09 | 54 | char *variable; |
d166f048 | 55 | int size; |
f73dda09 | 56 | char desired_setting[1]; /* actual size is `size' */ |
d166f048 JA |
57 | } SAVED_VAR; |
58 | ||
f73dda09 JA |
59 | /* If HEAD.CLEANUP is null, then ARG.V contains a tag to throw back to. |
60 | If HEAD.CLEANUP is restore_variable, then SV.V contains the saved | |
61 | variable. Otherwise, call HEAD.CLEANUP (ARG.V) to clean up. */ | |
62 | typedef union uwp { | |
63 | struct uwp_head { | |
64 | union uwp *next; | |
65 | Function *cleanup; | |
66 | } head; | |
67 | struct { | |
68 | struct uwp_head uwp_head; | |
69 | char *v; | |
70 | } arg; | |
71 | struct { | |
72 | struct uwp_head uwp_head; | |
73 | SAVED_VAR v; | |
74 | } sv; | |
75 | } UNWIND_ELT; | |
76 | ||
7117c2d2 | 77 | |
f73dda09 JA |
78 | static void without_interrupts __P((VFunction *, char *, char *)); |
79 | static void unwind_frame_discard_internal __P((char *, char *)); | |
80 | static void unwind_frame_run_internal __P((char *, char *)); | |
81 | static void add_unwind_protect_internal __P((Function *, char *)); | |
82 | static void remove_unwind_protect_internal __P((char *, char *)); | |
83 | static void run_unwind_protects_internal __P((char *, char *)); | |
84 | static void clear_unwind_protects_internal __P((char *, char *)); | |
85 | static inline void restore_variable __P((SAVED_VAR *)); | |
86 | static void unwind_protect_mem_internal __P((char *, char *)); | |
726f6388 JA |
87 | |
88 | static UNWIND_ELT *unwind_protect_list = (UNWIND_ELT *)NULL; | |
89 | ||
7117c2d2 JA |
90 | #define uwpalloc(elt) (elt) = (UNWIND_ELT *)xmalloc (sizeof (UNWIND_ELT)) |
91 | #define uwpfree(elt) free(elt) | |
726f6388 JA |
92 | |
93 | /* Run a function without interrupts. This relies on the fact that the | |
94 | FUNCTION cannot change the value of interrupt_immediately. (I.e., does | |
95 | not call QUIT (). */ | |
96 | static void | |
97 | without_interrupts (function, arg1, arg2) | |
98 | VFunction *function; | |
99 | char *arg1, *arg2; | |
100 | { | |
101 | int old_interrupt_immediately; | |
102 | ||
103 | old_interrupt_immediately = interrupt_immediately; | |
104 | interrupt_immediately = 0; | |
105 | ||
106 | (*function)(arg1, arg2); | |
107 | ||
108 | interrupt_immediately = old_interrupt_immediately; | |
109 | } | |
110 | ||
111 | /* Start the beginning of a region. */ | |
112 | void | |
113 | begin_unwind_frame (tag) | |
114 | char *tag; | |
115 | { | |
116 | add_unwind_protect ((Function *)NULL, tag); | |
117 | } | |
118 | ||
119 | /* Discard the unwind protects back to TAG. */ | |
120 | void | |
121 | discard_unwind_frame (tag) | |
122 | char *tag; | |
123 | { | |
124 | if (unwind_protect_list) | |
125 | without_interrupts (unwind_frame_discard_internal, tag, (char *)NULL); | |
126 | } | |
127 | ||
128 | /* Run the unwind protects back to TAG. */ | |
129 | void | |
130 | run_unwind_frame (tag) | |
131 | char *tag; | |
132 | { | |
133 | if (unwind_protect_list) | |
134 | without_interrupts (unwind_frame_run_internal, tag, (char *)NULL); | |
135 | } | |
136 | ||
137 | /* Add the function CLEANUP with ARG to the list of unwindable things. */ | |
138 | void | |
139 | add_unwind_protect (cleanup, arg) | |
140 | Function *cleanup; | |
141 | char *arg; | |
142 | { | |
143 | without_interrupts (add_unwind_protect_internal, (char *)cleanup, arg); | |
144 | } | |
145 | ||
146 | /* Remove the top unwind protect from the list. */ | |
147 | void | |
148 | remove_unwind_protect () | |
149 | { | |
150 | if (unwind_protect_list) | |
151 | without_interrupts | |
152 | (remove_unwind_protect_internal, (char *)NULL, (char *)NULL); | |
153 | } | |
154 | ||
155 | /* Run the list of cleanup functions in unwind_protect_list. */ | |
156 | void | |
157 | run_unwind_protects () | |
158 | { | |
159 | if (unwind_protect_list) | |
160 | without_interrupts | |
161 | (run_unwind_protects_internal, (char *)NULL, (char *)NULL); | |
162 | } | |
163 | ||
28ef6c31 JA |
164 | /* Erase the unwind-protect list. If flags is 1, free the elements. */ |
165 | void | |
166 | clear_unwind_protect_list (flags) | |
167 | int flags; | |
168 | { | |
f73dda09 JA |
169 | char *flag; |
170 | ||
28ef6c31 | 171 | if (unwind_protect_list) |
f73dda09 JA |
172 | { |
173 | flag = flags ? "" : (char *)NULL; | |
174 | without_interrupts | |
175 | (clear_unwind_protects_internal, flag, (char *)NULL); | |
176 | } | |
28ef6c31 JA |
177 | } |
178 | ||
3185942a JA |
179 | int |
180 | have_unwind_protects () | |
181 | { | |
182 | return (unwind_protect_list != 0); | |
183 | } | |
184 | ||
726f6388 JA |
185 | /* **************************************************************** */ |
186 | /* */ | |
28ef6c31 | 187 | /* The Actual Functions */ |
726f6388 JA |
188 | /* */ |
189 | /* **************************************************************** */ | |
190 | ||
191 | static void | |
192 | add_unwind_protect_internal (cleanup, arg) | |
193 | Function *cleanup; | |
194 | char *arg; | |
195 | { | |
196 | UNWIND_ELT *elt; | |
197 | ||
7117c2d2 | 198 | uwpalloc (elt); |
f73dda09 JA |
199 | elt->head.next = unwind_protect_list; |
200 | elt->head.cleanup = cleanup; | |
201 | elt->arg.v = arg; | |
726f6388 JA |
202 | unwind_protect_list = elt; |
203 | } | |
204 | ||
205 | static void | |
28ef6c31 JA |
206 | remove_unwind_protect_internal (ignore1, ignore2) |
207 | char *ignore1, *ignore2; | |
726f6388 | 208 | { |
d166f048 | 209 | UNWIND_ELT *elt; |
726f6388 | 210 | |
d166f048 | 211 | elt = unwind_protect_list; |
726f6388 JA |
212 | if (elt) |
213 | { | |
f73dda09 | 214 | unwind_protect_list = unwind_protect_list->head.next; |
7117c2d2 | 215 | uwpfree (elt); |
726f6388 JA |
216 | } |
217 | } | |
218 | ||
219 | static void | |
28ef6c31 JA |
220 | run_unwind_protects_internal (ignore1, ignore2) |
221 | char *ignore1, *ignore2; | |
726f6388 | 222 | { |
f73dda09 | 223 | unwind_frame_run_internal ((char *) NULL, (char *) NULL); |
726f6388 JA |
224 | } |
225 | ||
226 | static void | |
28ef6c31 JA |
227 | clear_unwind_protects_internal (flag, ignore) |
228 | char *flag, *ignore; | |
229 | { | |
f73dda09 | 230 | if (flag) |
28ef6c31 JA |
231 | { |
232 | while (unwind_protect_list) | |
233 | remove_unwind_protect_internal ((char *)NULL, (char *)NULL); | |
234 | } | |
235 | unwind_protect_list = (UNWIND_ELT *)NULL; | |
236 | } | |
237 | ||
238 | static void | |
239 | unwind_frame_discard_internal (tag, ignore) | |
240 | char *tag, *ignore; | |
726f6388 JA |
241 | { |
242 | UNWIND_ELT *elt; | |
243 | ||
244 | while (elt = unwind_protect_list) | |
245 | { | |
f73dda09 JA |
246 | unwind_protect_list = unwind_protect_list->head.next; |
247 | if (elt->head.cleanup == 0 && (STREQ (elt->arg.v, tag))) | |
726f6388 | 248 | { |
7117c2d2 | 249 | uwpfree (elt); |
726f6388 JA |
250 | break; |
251 | } | |
252 | else | |
7117c2d2 | 253 | uwpfree (elt); |
726f6388 JA |
254 | } |
255 | } | |
256 | ||
f73dda09 JA |
257 | /* Restore the value of a variable, based on the contents of SV. |
258 | sv->desired_setting is a block of memory SIZE bytes long holding the | |
259 | value itself. This block of memory is copied back into the variable. */ | |
260 | static inline void | |
261 | restore_variable (sv) | |
262 | SAVED_VAR *sv; | |
263 | { | |
264 | FASTCOPY (sv->desired_setting, sv->variable, sv->size); | |
265 | } | |
266 | ||
726f6388 | 267 | static void |
28ef6c31 JA |
268 | unwind_frame_run_internal (tag, ignore) |
269 | char *tag, *ignore; | |
726f6388 JA |
270 | { |
271 | UNWIND_ELT *elt; | |
272 | ||
273 | while (elt = unwind_protect_list) | |
274 | { | |
f73dda09 | 275 | unwind_protect_list = elt->head.next; |
726f6388 JA |
276 | |
277 | /* If tag, then compare. */ | |
f73dda09 | 278 | if (!elt->head.cleanup) |
726f6388 | 279 | { |
f73dda09 | 280 | if (tag && STREQ (elt->arg.v, tag)) |
726f6388 | 281 | { |
7117c2d2 | 282 | uwpfree (elt); |
726f6388 JA |
283 | break; |
284 | } | |
726f6388 JA |
285 | } |
286 | else | |
287 | { | |
f73dda09 JA |
288 | if (elt->head.cleanup == (Function *) restore_variable) |
289 | restore_variable (&elt->sv.v); | |
290 | else | |
291 | (*(elt->head.cleanup)) (elt->arg.v); | |
726f6388 | 292 | } |
726f6388 | 293 | |
7117c2d2 | 294 | uwpfree (elt); |
f73dda09 | 295 | } |
d166f048 | 296 | } |
726f6388 | 297 | |
726f6388 | 298 | static void |
f73dda09 JA |
299 | unwind_protect_mem_internal (var, psize) |
300 | char *var; | |
301 | char *psize; | |
726f6388 | 302 | { |
f73dda09 JA |
303 | int size, allocated; |
304 | UNWIND_ELT *elt; | |
726f6388 | 305 | |
f73dda09 JA |
306 | size = *(int *) psize; |
307 | allocated = size + offsetof (UNWIND_ELT, sv.v.desired_setting[0]); | |
308 | elt = (UNWIND_ELT *)xmalloc (allocated); | |
309 | elt->head.next = unwind_protect_list; | |
310 | elt->head.cleanup = (Function *) restore_variable; | |
311 | elt->sv.v.variable = var; | |
312 | elt->sv.v.size = size; | |
313 | FASTCOPY (var, elt->sv.v.desired_setting, size); | |
314 | unwind_protect_list = elt; | |
726f6388 JA |
315 | } |
316 | ||
317 | /* Save the value of a variable so it will be restored when unwind-protects | |
f73dda09 JA |
318 | are run. VAR is a pointer to the variable. SIZE is the size in |
319 | bytes of VAR. */ | |
726f6388 | 320 | void |
f73dda09 JA |
321 | unwind_protect_mem (var, size) |
322 | char *var; | |
726f6388 JA |
323 | int size; |
324 | { | |
f73dda09 | 325 | without_interrupts (unwind_protect_mem_internal, var, (char *) &size); |
726f6388 | 326 | } |