2 Unix SMB/CIFS implementation.
3 Implement a stack of talloc contexts
4 Copyright (C) Volker Lendecke 2007
5 Copyright (C) Jeremy Allison 2009 - made thread safe.
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 2 of the License, or
10 (at your option) any later version.
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.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 * Implement a stack of talloc frames.
25 * When a new talloc stackframe is allocated with talloc_stackframe(), then
26 * the TALLOC_CTX returned with talloc_tos() is reset to that new
27 * frame. Whenever that stack frame is TALLOC_FREE()'ed, then the reverse
28 * happens: The previous talloc_tos() is restored.
30 * This API is designed to be robust in the sense that if someone forgets to
31 * TALLOC_FREE() a stackframe, then the next outer one correctly cleans up and
32 * resets the talloc_tos().
34 * This robustness feature means that we can't rely on a linked list with
35 * talloc destructors because in a hierarchy of talloc destructors the parent
36 * destructor is called before its children destructors. The child destructor
37 * called after the parent would set the talloc_tos() to the wrong value.
42 struct talloc_stackframe {
44 int talloc_stack_arraysize;
45 TALLOC_CTX **talloc_stack;
49 * In the single threaded case this is a pointer
50 * to the global talloc_stackframe. In the MT-case
51 * this is the pointer to the thread-specific key
52 * used to look up the per-thread talloc_stackframe
56 static void *global_ts;
58 /* Variable to ensure TLS value is only initialized once. */
59 static smb_thread_once_t ts_initialized = SMB_THREAD_ONCE_INIT;
61 static void talloc_stackframe_init(void * unused)
63 if (SMB_THREAD_CREATE_TLS("talloc_stackframe", global_ts)) {
64 smb_panic("talloc_stackframe_init create_tls failed");
68 static struct talloc_stackframe *talloc_stackframe_create(void)
70 #if defined(PARANOID_MALLOC_CHECKER)
75 struct talloc_stackframe *ts = (struct talloc_stackframe *)calloc(
76 1, sizeof(struct talloc_stackframe));
77 #if defined(PARANOID_MALLOC_CHECKER)
78 #define calloc(n, s) __ERROR_DONT_USE_MALLOC_DIRECTLY
82 smb_panic("talloc_stackframe_init malloc failed");
85 SMB_THREAD_ONCE(&ts_initialized, talloc_stackframe_init, NULL);
87 if (SMB_THREAD_SET_TLS(global_ts, ts)) {
88 smb_panic("talloc_stackframe_init set_tls failed");
93 static int talloc_pop(TALLOC_CTX *frame)
95 struct talloc_stackframe *ts =
96 (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
99 for (i=ts->talloc_stacksize-1; i>0; i--) {
100 if (frame == ts->talloc_stack[i]) {
103 TALLOC_FREE(ts->talloc_stack[i]);
106 ts->talloc_stack[i] = NULL;
107 ts->talloc_stacksize = i;
112 * Create a new talloc stack frame.
114 * When free'd, it frees all stack frames that were created after this one and
115 * not explicitly freed.
118 static TALLOC_CTX *talloc_stackframe_internal(const char *location,
121 TALLOC_CTX **tmp, *top;
122 struct talloc_stackframe *ts =
123 (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
126 ts = talloc_stackframe_create();
129 if (ts->talloc_stack_arraysize < ts->talloc_stacksize + 1) {
130 tmp = talloc_realloc(NULL, ts->talloc_stack, TALLOC_CTX *,
131 ts->talloc_stacksize + 1);
135 ts->talloc_stack = tmp;
136 ts->talloc_stack_arraysize = ts->talloc_stacksize + 1;
140 top = talloc_pool(ts->talloc_stack, poolsize);
143 /* We chain parentage, so if one is a pool we draw from it. */
144 if (ts->talloc_stacksize == 0) {
145 parent = ts->talloc_stack;
147 parent = ts->talloc_stack[ts->talloc_stacksize-1];
149 top = talloc_new(parent);
155 talloc_set_name_const(top, location);
156 talloc_set_destructor(top, talloc_pop);
158 ts->talloc_stack[ts->talloc_stacksize++] = top;
162 smb_panic("talloc_stackframe failed");
166 TALLOC_CTX *_talloc_stackframe(const char *location)
168 return talloc_stackframe_internal(location, 0);
171 TALLOC_CTX *_talloc_stackframe_pool(const char *location, size_t poolsize)
173 return talloc_stackframe_internal(location, poolsize);
177 * Get us the current top of the talloc stack.
180 TALLOC_CTX *talloc_tos(void)
182 struct talloc_stackframe *ts =
183 (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
185 if (ts == NULL || ts->talloc_stacksize == 0) {
187 ts = (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
188 DEBUG(0, ("no talloc stackframe around, leaking memory\n"));
191 return ts->talloc_stack[ts->talloc_stacksize-1];
195 * return true if a talloc stackframe exists
196 * this can be used to prevent memory leaks for code that can
197 * optionally use a talloc stackframe (eg. nt_errstr())
200 bool talloc_stackframe_exists(void)
202 struct talloc_stackframe *ts =
203 (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
205 if (ts == NULL || ts->talloc_stacksize == 0) {