2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1990, 1993
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7 * This code is derived from software contributed to Berkeley by
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22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)atexit.c 8.2 (Berkeley) 7/3/94";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
41 #include "namespace.h"
49 #include "un-namespace.h"
50 #include "block_abi.h"
52 #include "libc_private.h"
55 * The _Block_copy() function is provided by the block runtime.
57 __attribute__((weak)) void*
60 #define ATEXIT_FN_EMPTY 0
61 #define ATEXIT_FN_STD 1
62 #define ATEXIT_FN_CXA 2
64 static pthread_mutex_t atexit_mutex = PTHREAD_MUTEX_INITIALIZER;
66 #define _MUTEX_LOCK(x) if (__isthreaded) _pthread_mutex_lock(x)
67 #define _MUTEX_UNLOCK(x) if (__isthreaded) _pthread_mutex_unlock(x)
68 #define _MUTEX_DESTROY(x) if (__isthreaded) _pthread_mutex_destroy(x)
71 struct atexit *next; /* next in list */
72 int ind; /* next index in this table */
74 int fn_type; /* ATEXIT_? from above */
76 void (*std_func)(void);
77 void (*cxa_func)(void *);
78 } fn_ptr; /* function pointer */
79 void *fn_arg; /* argument for CXA callback */
80 void *fn_dso; /* shared module handle */
81 } fns[ATEXIT_SIZE]; /* the table itself */
84 static struct atexit *__atexit; /* points to head of LIFO stack */
85 typedef DECLARE_BLOCK(void, atexit_block, void);
87 int atexit_b(atexit_block);
88 int __cxa_atexit(void (*)(void *), void *, void *);
91 * Register the function described by 'fptr' to be called at application
92 * exit or owning shared object unload time. This is a helper function
93 * for atexit and __cxa_atexit.
96 atexit_register(struct atexit_fn *fptr)
98 static struct atexit __atexit0; /* one guaranteed table */
101 _MUTEX_LOCK(&atexit_mutex);
102 if ((p = __atexit) == NULL)
103 __atexit = p = &__atexit0;
104 else while (p->ind >= ATEXIT_SIZE) {
105 struct atexit *old__atexit;
106 old__atexit = __atexit;
107 _MUTEX_UNLOCK(&atexit_mutex);
108 if ((p = (struct atexit *)malloc(sizeof(*p))) == NULL)
110 _MUTEX_LOCK(&atexit_mutex);
111 if (old__atexit != __atexit) {
112 /* Lost race, retry operation */
113 _MUTEX_UNLOCK(&atexit_mutex);
115 _MUTEX_LOCK(&atexit_mutex);
123 p->fns[p->ind++] = *fptr;
124 _MUTEX_UNLOCK(&atexit_mutex);
129 * Register a function to be performed at exit.
132 atexit(void (*func)(void))
137 fn.fn_type = ATEXIT_FN_STD;
138 fn.fn_ptr.std_func = func;
142 error = atexit_register(&fn);
145 __weak_reference(atexit, __libc_atexit);
148 * Register a block to be performed at exit.
151 atexit_b(atexit_block func)
155 if (_Block_copy == 0) {
159 func = _Block_copy(func);
161 // Blocks are not C++ destructors, but they have the same signature (a
162 // single void* parameter), so we can pretend that they are.
163 fn.fn_type = ATEXIT_FN_CXA;
164 fn.fn_ptr.cxa_func = (void(*)(void*))GET_BLOCK_FUNCTION(func);
168 error = atexit_register(&fn);
173 * Register a function to be performed at exit or when an shared object
174 * with given dso handle is unloaded dynamically.
177 __cxa_atexit(void (*func)(void *), void *arg, void *dso)
182 fn.fn_type = ATEXIT_FN_CXA;
183 fn.fn_ptr.cxa_func = func;
187 error = atexit_register(&fn);
191 #pragma weak __pthread_cxa_finalize
192 void __pthread_cxa_finalize(const struct dl_phdr_info *);
194 static int global_exit;
197 * Call all handlers registered with __cxa_atexit for the shared
198 * object owning 'dso'. Note: if 'dso' is NULL, then all remaining
199 * handlers are called.
202 __cxa_finalize(void *dso)
204 struct dl_phdr_info phdr_info;
210 has_phdr = _rtld_addr_phdr(dso, &phdr_info);
216 _MUTEX_LOCK(&atexit_mutex);
217 for (p = __atexit; p; p = p->next) {
218 for (n = p->ind; --n >= 0;) {
219 if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
220 continue; /* already been called */
222 if (dso != NULL && dso != fn.fn_dso) {
224 if (!has_phdr || global_exit ||
225 !__elf_phdr_match_addr(&phdr_info,
230 Mark entry to indicate that this particular handler
231 has already been called.
233 p->fns[n].fn_type = ATEXIT_FN_EMPTY;
234 _MUTEX_UNLOCK(&atexit_mutex);
236 /* Call the function of correct type. */
237 if (fn.fn_type == ATEXIT_FN_CXA)
238 fn.fn_ptr.cxa_func(fn.fn_arg);
239 else if (fn.fn_type == ATEXIT_FN_STD)
240 fn.fn_ptr.std_func();
241 _MUTEX_LOCK(&atexit_mutex);
244 _MUTEX_UNLOCK(&atexit_mutex);
246 _MUTEX_DESTROY(&atexit_mutex);
248 if (has_phdr && !global_exit && &__pthread_cxa_finalize != NULL)
249 __pthread_cxa_finalize(&phdr_info);