/* * 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 #include #include /* SunOS's losing assert.h needs it */ #include #include #include #include #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(); }