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/* FUNCTION <<signal>>---specify handler subroutine for a signal INDEX signal INDEX _signal_r INDEX raise INDEX _raise_r ANSI_SYNOPSIS #include <signal.h> void ( * signal(int <[sig]>, void(*<[func]>)(int)) )(int); void ( * _signal_r(void *<[reent]>, int <[sig]>, void(*<[func]>)(int)) )(int); int raise (int <[sig]>); int _raise_r (void *<[reent]>, int <[sig]>); TRAD_SYNOPSIS #include <signal.h> char ( * signal(<[sig]>, <[func]>) )() int <[sig]>; char ( * <[func]> )(); char ( * _signal_r(<[reent]>, <[sig]>, <[func]>) )() char *<[reent]>; int <[sig]>; char ( * <[func]> )(); int raise (<[sig]>)() int <[sig]>; int _raise_r (<[reent]>, <[sig]>)() char *<[reent]>; int <[sig]>; DESCRIPTION <<signal, raise>> provide a simple signal/raise implementation for embedded targets. <<signal>> allows you to request changed treatment for a particular signal <[sig]>. You can use one of the predefined macros <<SIG_DFL>> (select system default handling) or <<SIG_IGN>> (ignore this signal) as the value of <[func]>; otherwise, <[func]> is a function pointer that identifies a subroutine in your program as the handler for this signal. Some of the execution environment for signal handlers is unpredictable; notably, the only library function required to work correctly from within a signal handler is @code{signal} itself, and only when used to redefine the handler for the current signal value. Static storage is likewise unreliable for signal handlers, with one exception: if you declare a static storage location as `<<volatile sig_atomic_t>>', then you may use that location in a signal handler to store signal values. If your signal handler terminates using <<return>> (or implicit return), your program's execution continues at the point where it was when the signal was raised (whether by your program itself, or by an external event). Signal handlers can also use functions such as <<exit>> and <<abort>> to avoid returning. <<raise>> sends the signal sig to the executing program. It returns zero if successful, non-zero if unsuccessful. The alternate functions <<_signal_r, _raise_r>> are the reentrant versions. The extra argument <[reent]> is a pointer to a reentrancy structure. @c FIXME: do we have setjmp.h and assoc fns? RETURNS If your request for a signal handler cannot be honored, the result is <<SIG_ERR>>; a specific error number is also recorded in <<errno>>. Otherwise, the result is the previous handler (a function pointer or one of the predefined macros). PORTABILITY ANSI C requires <<raise>>, <<signal>>. No supporting OS subroutines are required to link with <<signal>>, but it will not have any useful effects, except for software generated signals, without an operating system that can actually raise exceptions. */ /* * signal.c * Original Author: G. Haley * * signal associates the function pointed to by func with the signal sig. When * a signal occurs, the value of func determines the action taken as follows: * if func is SIG_DFL, the default handling for that signal will occur; if func * is SIG_IGN, the signal will be ignored; otherwise, the default handling for * the signal is restored (SIG_DFL), and the function func is called with sig * as its argument. Returns the value of func for the previous call to signal * for the signal sig, or SIG_ERR if the request fails. */ /* _init_signal initialises the signal handlers for each signal. This function is called by crt0 at program startup. */ #ifdef SIGNAL_PROVIDED int _dummy_simulated_signal; #else #include <errno.h> #include <signal.h> #include <stddef.h> #include <stdlib.h> #include <reent.h> #include <_syslist.h> int _DEFUN (_init_signal_r, (ptr), struct _reent *ptr) { int i; if (ptr->_sig_func == NULL) { ptr->_sig_func = (_sig_func_ptr *)_malloc_r (ptr, sizeof (_sig_func_ptr) * NSIG); if (ptr->_sig_func == NULL) return -1; for (i = 0; i < NSIG; i++) ptr->_sig_func[i] = SIG_DFL; } return 0; } _sig_func_ptr _DEFUN (_signal_r, (ptr, sig, func), struct _reent *ptr _AND int sig _AND _sig_func_ptr func) { _sig_func_ptr old_func, *temp; if (sig < 0 || sig >= NSIG) { ptr->_errno = EINVAL; return SIG_ERR; } if (ptr->_sig_func == NULL && _init_signal_r (ptr) != 0) return SIG_ERR; old_func = ptr->_sig_func[sig]; ptr->_sig_func[sig] = func; return old_func; } int _raise_r (ptr, sig) struct _reent *ptr; int sig; { _sig_func_ptr func; int result = 0; if (sig < 0 || sig >= NSIG) { ptr->_errno = EINVAL; return -1; } if (ptr->_sig_func == NULL && _init_signal_r (ptr) != 0) return -1; switch ((_POINTER_INT) ptr->_sig_func[sig]) { case SIG_DFL: return _kill_r (ptr, _getpid_r (ptr), sig); case SIG_IGN: break; case SIG_ERR: ptr->_errno = EINVAL; result = 1; break; default: func = ptr->_sig_func[sig]; ptr->_sig_func[sig] = SIG_DFL; func (sig); break; } return result; } int __sigtramp_r (ptr, sig) struct _reent *ptr; int sig; { _sig_func_ptr func; if (sig < 0 || sig >= NSIG) { return -1; } if (ptr->_sig_func == NULL && _init_signal_r (ptr) != 0) return -1; switch ((_POINTER_INT) ptr->_sig_func[sig]) { case SIG_DFL: return 1; case SIG_ERR: return 2; case SIG_IGN: return 3; default: func = ptr->_sig_func[sig]; ptr->_sig_func[sig] = SIG_DFL; func (sig); return 0; } } #ifndef _REENT_ONLY int raise (sig) int sig; { return _raise_r (_REENT, sig); } _sig_func_ptr _DEFUN (signal, (sig, func), int sig _AND _sig_func_ptr func) { return _signal_r (_REENT, sig, func); } int _init_signal () { return _init_signal_r (_REENT); } int __sigtramp (int sig) { return __sigtramp_r (_REENT, sig); } #endif #endif /* !SIGNAL_PROVIDED */
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