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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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 #include "namespace.h"
47 #include "un-namespace.h"
48 #include "block_abi.h"
50 #include "libc_private.h"
53 * The _Block_copy() function is provided by the block runtime.
55 __attribute__((weak)) void*
58 #define ATEXIT_FN_EMPTY 0
59 #define ATEXIT_FN_STD 1
60 #define ATEXIT_FN_CXA 2
62 static pthread_mutex_t atexit_mutex = PTHREAD_MUTEX_INITIALIZER;
64 #define _MUTEX_LOCK(x) if (__isthreaded) _pthread_mutex_lock(x)
65 #define _MUTEX_UNLOCK(x) if (__isthreaded) _pthread_mutex_unlock(x)
66 #define _MUTEX_DESTROY(x) if (__isthreaded) _pthread_mutex_destroy(x)
69 struct atexit *next; /* next in list */
70 int ind; /* next index in this table */
72 int fn_type; /* ATEXIT_? from above */
74 void (*std_func)(void);
75 void (*cxa_func)(void *);
76 } fn_ptr; /* function pointer */
77 void *fn_arg; /* argument for CXA callback */
78 void *fn_dso; /* shared module handle */
79 } fns[ATEXIT_SIZE]; /* the table itself */
82 static struct atexit *__atexit; /* points to head of LIFO stack */
83 typedef DECLARE_BLOCK(void, atexit_block, void);
85 int atexit_b(atexit_block);
86 int __cxa_atexit(void (*)(void *), void *, void *);
89 * Register the function described by 'fptr' to be called at application
90 * exit or owning shared object unload time. This is a helper function
91 * for atexit and __cxa_atexit.
94 atexit_register(struct atexit_fn *fptr)
96 static struct atexit __atexit0; /* one guaranteed table */
99 _MUTEX_LOCK(&atexit_mutex);
100 if ((p = __atexit) == NULL)
101 __atexit = p = &__atexit0;
102 else while (p->ind >= ATEXIT_SIZE) {
103 struct atexit *old__atexit;
104 old__atexit = __atexit;
105 _MUTEX_UNLOCK(&atexit_mutex);
106 if ((p = (struct atexit *)malloc(sizeof(*p))) == NULL)
108 _MUTEX_LOCK(&atexit_mutex);
109 if (old__atexit != __atexit) {
110 /* Lost race, retry operation */
111 _MUTEX_UNLOCK(&atexit_mutex);
113 _MUTEX_LOCK(&atexit_mutex);
121 p->fns[p->ind++] = *fptr;
122 _MUTEX_UNLOCK(&atexit_mutex);
127 * Register a function to be performed at exit.
130 atexit(void (*func)(void))
135 fn.fn_type = ATEXIT_FN_STD;
136 fn.fn_ptr.std_func = func;
140 error = atexit_register(&fn);
143 __weak_reference(atexit, __libc_atexit);
146 * Register a block to be performed at exit.
149 atexit_b(atexit_block func)
153 if (_Block_copy == 0) {
157 func = _Block_copy(func);
159 // Blocks are not C++ destructors, but they have the same signature (a
160 // single void* parameter), so we can pretend that they are.
161 fn.fn_type = ATEXIT_FN_CXA;
162 fn.fn_ptr.cxa_func = (void(*)(void*))GET_BLOCK_FUNCTION(func);
166 error = atexit_register(&fn);
171 * Register a function to be performed at exit or when an shared object
172 * with given dso handle is unloaded dynamically.
175 __cxa_atexit(void (*func)(void *), void *arg, void *dso)
180 fn.fn_type = ATEXIT_FN_CXA;
181 fn.fn_ptr.cxa_func = func;
185 error = atexit_register(&fn);
189 #pragma weak __pthread_cxa_finalize
190 void __pthread_cxa_finalize(const struct dl_phdr_info *);
192 static int global_exit;
195 * Call all handlers registered with __cxa_atexit for the shared
196 * object owning 'dso'. Note: if 'dso' is NULL, then all remaining
197 * handlers are called.
200 __cxa_finalize(void *dso)
202 struct dl_phdr_info phdr_info;
208 has_phdr = _rtld_addr_phdr(dso, &phdr_info);
214 _MUTEX_LOCK(&atexit_mutex);
215 for (p = __atexit; p; p = p->next) {
216 for (n = p->ind; --n >= 0;) {
217 if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
218 continue; /* already been called */
220 if (dso != NULL && dso != fn.fn_dso) {
222 if (!has_phdr || global_exit ||
223 !__elf_phdr_match_addr(&phdr_info,
228 Mark entry to indicate that this particular handler
229 has already been called.
231 p->fns[n].fn_type = ATEXIT_FN_EMPTY;
232 _MUTEX_UNLOCK(&atexit_mutex);
234 /* Call the function of correct type. */
235 if (fn.fn_type == ATEXIT_FN_CXA)
236 fn.fn_ptr.cxa_func(fn.fn_arg);
237 else if (fn.fn_type == ATEXIT_FN_STD)
238 fn.fn_ptr.std_func();
239 _MUTEX_LOCK(&atexit_mutex);
242 _MUTEX_UNLOCK(&atexit_mutex);
244 _MUTEX_DESTROY(&atexit_mutex);
246 if (has_phdr && !global_exit && &__pthread_cxa_finalize != NULL)
247 __pthread_cxa_finalize(&phdr_info);