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/*
* Copyright (C) 2019 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef SC_PANIC_H
#define SC_PANIC_H
#include <stdarg.h>
/**
* sc_panic is an exit-with-message utility function.
*
* The function takes a printf-like format string that is formatted and printed
* somehow. The function then terminates the process by calling exit. Both
* aspects can be customized.
*
* The particular nature of the exit can be customized by calling
* sc_set_panic_action. The panic action is a function that is called before
* attempting to exit.
*
* The way the error message is formatted and printed can be customized by
* calling sc_set_panic_format_fn(). By default the error is printed to
* standard error. If the error is related to a system call failure then errno
* can be set to a non-zero value just prior to calling sc_panic. The value
* will then be used when crafting the error message.
**/
__attribute__((noreturn, format(printf, 1, 2))) void sc_panic(const char *fmt, ...);
/**
* sc_panicv is a variant of sc_panic with an argument list.
**/
__attribute__((noreturn)) void sc_panicv(const char *fmt, va_list ap);
/**
* sc_panic_exit_fn is the type of the exit function used by sc_panic().
**/
typedef void (*sc_panic_exit_fn)(void);
/**
* sc_set_panic_exit_fn sets the panic exit function.
*
* When sc_panic is called it will eventually exit the running process. Just
* prior to that, it will call the panic exit function, if one has been set.
*
* If exiting the process is undesired, for example while running in intrd as
* pid 1, during the system shutdown phase, then a process can set the panic
* exit function. Note that if the specified function returns then panic will
* proceed to call exit(3) anyway.
*
* The old exit function, if any, is returned.
**/
sc_panic_exit_fn sc_set_panic_exit_fn(sc_panic_exit_fn fn);
/**
* sc_panic_msg_fn is the type of the format function used by sc_panic().
**/
typedef void (*sc_panic_msg_fn)(const char *fmt, va_list ap, int errno_copy);
/**
* sc_set_panic_msg_fn sets the panic message function.
*
* When sc_panic is called it will attempt to print an error message to
* standard error. The message includes information provided by the caller: the
* format string, the argument vector for a printf-like function as well as a
* copy of the system errno value, which may be zero if the error is not
* originated by a system call error.
*
* If custom formatting of the error message is desired, for example while
* running in initrd as pid 1, during the system shutdown phase, then a process
* can set the panic message function. Once set the function takes over the
* responsibility of printing an error message (in whatever form is
* appropriate).
*
* The old message function, if any, is returned.
**/
sc_panic_msg_fn sc_set_panic_msg_fn(sc_panic_msg_fn fn);
#endif
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