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#ifndef RBIMPL_INTERN_SIGNAL_H /*-*-C++-*-vi:se ft=cpp:*/
#define RBIMPL_INTERN_SIGNAL_H
/**
* @file
* @author Ruby developers <ruby-core@ruby-lang.org>
* @copyright This file is a part of the programming language Ruby.
* Permission is hereby granted, to either redistribute and/or
* modify this file, provided that the conditions mentioned in the
* file COPYING are met. Consult the file for details.
* @warning Symbols prefixed with either `RBIMPL` or `rbimpl` are
* implementation details. Don't take them as canon. They could
* rapidly appear then vanish. The name (path) of this header file
* is also an implementation detail. Do not expect it to persist
* at the place it is now. Developers are free to move it anywhere
* anytime at will.
* @note To ruby-core: remember that this header can be possibly
* recursively included from extension libraries written in C++.
* Do not expect for instance `__VA_ARGS__` is always available.
* We assume C99 for ruby itself but we don't assume languages of
* extension libraries. They could be written in C++98.
* @brief Signal handling APIs.
*/
#include "ruby/internal/attr/nonnull.h"
#include "ruby/internal/attr/pure.h"
#include "ruby/internal/dllexport.h"
#include "ruby/internal/value.h"
RBIMPL_SYMBOL_EXPORT_BEGIN()
/* signal.c */
RBIMPL_ATTR_NONNULL(())
/**
* Sends a signal ("kills") to processes.
*
* The first argument is the signal, either in:
*
* - Numerical representation (e.g. `9`), or
* - Textual representation of canonical (e.g. `:SIGKILL`) name or
* abbreviated (e.g. `:KILL`) name, either in ::rb_cSymbol or ::rb_cString.
*
* All the remaining arguments are numerical representations of process IDs.
* This function iterates over them to send the specified signal.
*
* You can specify both negative PIDs and negative signo to this function:
*
* ```
* sig \ pid | >= 1 | == 0 | == -1 | <= -2
* ===========+======+======+=======+=======
* > 0 | #1 | #2 | #3 | #4
* == 0 | #5 | #6 | #7 | #8
* < 0 | #9 | #10 | #11
* ```
*
* - Case #1: When signo and PID are both positive, this function sends the
* specified signal to the specified process (intuitive).
*
* - Case #2: When signo is positive and PID is zero, this function sends
* that signal to the current process group.
*
* - Case #3: When signo is positive and PID is -1, this function sends that
* signal to everything that the current process is allowed to kill.
*
* - Case #4: When signo is positive and PID is negative (but not -1), this
* function sends that signal to every processes in a process group, whose
* process group ID is the absolute value of the passed PID.
*
* - Case #5: When signo is zero and PID is positive, this function just
* checks for the existence of the specified process and doesn't send
* anything to anyone. In case the process is absent `Errno::ESRCH` is
* raised.
*
* - Case #6: When signo and PID are both zero, this function checks for the
* existence of the current process group. And it must do. This function
* is effectively a no-op then.
*
* - Case #7: When signo is zero and PID is -1, this function checks if there
* is any other process that the current process can kill. At least init
* (PID 1) must exist, so this must not fail.
*
* - Case #8: When signo is zero and PID is negative (but not -1), this
* function checks if there is a process group whose process group ID is
* the absolute value of the passed PID. In case the process group is
* absent `Errno::ESRCH` is raised.
*
* - Case #9: When signo is negative and PID is positive, this function sends
* the absolute value of the passed signo to the process group specified as
* the PID.
*
* - Case #10: When signo is negative and PID is zero, it is highly expected
* that this function sends the absolute value of the passed signo to the
* current process group. Strictly speaking, IEEE Std 1003.1-2017
* specifies that this (`killpg(3posix)` with an argument of zero) is an
* undefined behaviour. But no operating system is known so far that does
* things differently.
*
* - Case #11: When signo and PID are both negative, the behaviour of this
* function depends on how `killpg(3)` works. On Linux, it seems such
* attempt is strictly prohibited and `Errno::EINVAL` is raised. But on
* macOS, it seems it tries to to send the signal actually to the process
* group.
*
* @note Above description is in fact different from how `kill(2)` works.
* We interpret the passed arguments before passing them through to
* system calls.
* @param[in] argc Number of objects in `argv`.
* @param[in] argv Signal, followed by target PIDs.
* @exception rb_eArgError Unknown signal name.
* @exception rb_eSystemCallError Various errors sending signal to processes.
* @return Something numeric. The meaning of this return value is unclear.
* It seems in case of #1 above, this could be the body count. But
* other cases remain mysterious.
*/
VALUE rb_f_kill(int argc, const VALUE *argv);
/* This must be private, @shyouhei guesses. */
#ifdef POSIX_SIGNAL
#define posix_signal ruby_posix_signal
void (*posix_signal(int, void (*)(int)))(int);
#endif
RBIMPL_ATTR_PURE()
/**
* Queries the name of the signal. It returns for instance `"KILL"` for
* SIGKILL.
*
* @param[in] signo Signal number to query.
* @retval 0 No such signal.
* @retval otherwise A pointer to a static C string that is the name of
* the signal.
* @warning Don't free the return value.
*/
const char *ruby_signal_name(int signo);
/**
* Pretends as if there was no custom signal handler. This function sets the
* signal action to SIG_DFL, then kills itself.
*
* @param[in] sig The signal.
* @post Previous signal handler is lost.
* @post Passed signal is sent to the current process.
*
* @internal
*
* @shyouhei doesn't understand the needs of this function being visible from
* extension libraries.
*/
void ruby_default_signal(int sig);
RBIMPL_SYMBOL_EXPORT_END()
#endif /* RBIMPL_INTERN_SIGNAL_H */
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