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Diffstat (limited to '')
| -rw-r--r-- | lib/cleanup.c | 279 |
1 files changed, 279 insertions, 0 deletions
diff --git a/lib/cleanup.c b/lib/cleanup.c new file mode 100644 index 0000000..02bef2a --- /dev/null +++ b/lib/cleanup.c @@ -0,0 +1,279 @@ +/* + * cleanup.c -- simple dynamic cleanup function management + * Copyright (C) 1995 Markus Armbruster. + * Copyright (C) 2007 Colin Watson. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Library General Public + * License as published by the Free Software Foundation; either + * version 2 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Library General Public License for more details. + * + * You should have received a copy of the GNU Library General Public + * License along with this library; see the file docs/COPYING.LIB. If not, + * write to the Free Software Foundation, Inc., 51 Franklin St, Fifth + * Floor, Boston, MA 02110-1301 USA. +*/ + +#ifdef HAVE_CONFIG_H +# include "config.h" +#endif /* HAVE_CONFIG_H */ + +#include <stdbool.h> +#include <stdlib.h> +#include <stdio.h> /* SunOS's losing assert.h needs it */ +#include <assert.h> +#include <signal.h> +#include <unistd.h> +#include <string.h> + +#include "xalloc.h" + +#include "manconfig.h" /* for FATAL */ +#include "cleanup.h" + + + +/* Dealing with signals */ + + +/* saved signal actions */ +#ifdef SIGHUP +static struct sigaction saved_hup_action; +#endif /* SIGHUP */ +static struct sigaction saved_int_action; +static struct sigaction saved_term_action; + + +/* Run cleanups, then reraise signal with default handler. */ +static _Noreturn void +sighandler (int signo) +{ + struct sigaction act; + sigset_t set; + + do_cleanups_sigsafe (true); + + /* set default signal action */ + memset (&act, 0, sizeof act); + act.sa_handler = SIG_DFL; + sigemptyset (&act.sa_mask); + act.sa_flags = 0; + if (sigaction (signo, &act, NULL)) { + /* should not happen */ + _exit (FATAL); /* exit() is taboo from signal handlers! */ + } + + /* unmask signo */ + if ( sigemptyset (&set) + || sigaddset (&set, signo) + || sigprocmask (SIG_UNBLOCK, &set, NULL)) { + /* shouldn't happen */ + _exit (FATAL); /* exit() is taboo from signal handlers! */ + } + + /* signal has now default action and is unmasked, + reraise it to terminate program abnormally */ + raise (signo); + abort(); +} + + +/* Save signo's current action to oldact, if its handler is SIG_DFL + install sighandler, return 0 on success, -1 on failure. */ +static int +trap_signal (int signo, struct sigaction *oldact) +{ + if (sigaction (signo, NULL, oldact)) { + return -1; + } + + if (oldact->sa_handler == SIG_DFL) { + struct sigaction act; + + memset (&act, 0, sizeof act); + act.sa_handler = sighandler; + sigemptyset (&act.sa_mask); + act.sa_flags = 0; + return sigaction (signo, &act, oldact); + } + + return 0; +} + + +/* Trap some abnormal exits to call do_cleanups(). */ +static int +trap_abnormal_exits (void) +{ +#ifdef SIGHUP + if (trap_signal (SIGHUP, &saved_hup_action)) + return -1; +#endif /* SIGHUP */ + if (trap_signal (SIGINT, &saved_int_action)) + return -1; + if (trap_signal (SIGTERM, &saved_term_action)) + return -1; + return 0; +} + + +/* Restore signo's action from oldact if its current handler is + sighandler, return 0 on success, -1 on failure. */ +static int +untrap_signal (int signo, struct sigaction *oldact) +{ + struct sigaction act; + if (sigaction (signo, NULL, &act)) { + return -1; + } + + if (act.sa_handler == sighandler) { + return sigaction (signo, oldact, NULL); + } + + return 0; +} + + +/* Undo a previous trap_abnormal_exits(). */ +static int +untrap_abnormal_exits (void) +{ +#ifdef SIGHUP + if (untrap_signal (SIGHUP, &saved_hup_action)) + return -1; +#endif /* SIGHUP */ + if (untrap_signal (SIGINT, &saved_int_action)) + return -1; + if (untrap_signal (SIGTERM, &saved_term_action)) + return -1; + return 0; +} + + + +typedef struct { + cleanup_fun fun; + void *arg; + int sigsafe; +} slot; + +static slot *stack = NULL; /* stack of cleanup functions */ +static unsigned nslots = 0; /* #slots in stack */ +static unsigned tos = 0; /* top of stack, 0 <= tos <= nslots */ + +/* Call cleanup functions in stack from from top to bottom, + * Automatically called on program termination via exit(3) or default + * action for SIGHUP, SIGINT or SIGTERM. + * Since this may be called from a signal handler, do not use free(). + * If in_sighandler is true, cleanup functions with sigsafe=0 will not be + * called. + */ +void +do_cleanups_sigsafe (bool in_sighandler) +{ + unsigned i; + + assert (tos <= nslots); + for (i = tos; i > 0; --i) + if (!in_sighandler || stack[i-1].sigsafe) + stack[i-1].fun (stack[i-1].arg); +} + +/* Call cleanup functions in stack from from top to bottom, + * Automatically called on program termination via exit(3). + */ +void +do_cleanups (void) +{ + do_cleanups_sigsafe (false); + tos = 0; + nslots = 0; + free (stack); + stack = NULL; +} + + +/* Push a cleanup function on the cleanup stack, + * return 0 on success, -1 on failure. + * Caution: the cleanup function may be called from signal handlers if + * sigsafe=1. If you just want a convenient atexit() wrapper, pass + * sigsafe=0. + */ +int +push_cleanup (cleanup_fun fun, void *arg, int sigsafe) +{ + static bool handler_installed = false; + + assert (tos <= nslots); + + if (!handler_installed) { + if (atexit (do_cleanups)) + return -1; + handler_installed = true; + } + + if (tos == nslots) { + /* stack is full, allocate another slot */ + /* stack is not expected to grow much, otherwise we would double it */ + slot *new_stack; + + if (stack) { + new_stack = xnrealloc (stack, nslots+1, sizeof (slot)); + } else { + new_stack = xnmalloc (nslots+1, sizeof (slot)); + } + + if (!new_stack) return -1; + stack = new_stack; + ++nslots; + } + + assert (tos < nslots); + stack[tos].fun = fun; + stack[tos].arg = arg; + stack[tos].sigsafe = sigsafe; + ++tos; + + + trap_abnormal_exits(); + + return 0; +} + + +/* Remove topmost cleanup function from the cleanup stack that matches the + * given values. + */ +void +pop_cleanup (cleanup_fun fun, void *arg) +{ + unsigned i, j; + + assert (tos > 0); + + for (i = tos; i > 0; --i) { + if (stack[i-1].fun == fun && stack[i-1].arg == arg) { + for (j = i; j < tos; ++j) + stack[j-1] = stack[j]; + --tos; + break; + } + } + + if (tos == 0) untrap_abnormal_exits(); +} + + +/* Pop all cleanup functions from the cleanup stack. */ +void +pop_all_cleanups (void) +{ + tos = 0; + untrap_abnormal_exits(); +} |