92 lines
3.4 KiB
C
92 lines
3.4 KiB
C
/* Signal handling <signal.h>
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This file is part of the Public Domain C Library (PDCLib).
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Permission is granted to use, modify, and / or redistribute at will.
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*/
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#ifndef _PDCLIB_SIGNAL_H
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#define _PDCLIB_SIGNAL_H _PDCLIB_SIGNAL_H
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#include "pdclib/_PDCLIB_internal.h"
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/* Signals ------------------------------------------------------------------ */
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/* A word on signals, to the people using PDCLib in their OS projects.
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The definitions of the C standard leave about everything that *could* be
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useful to be "implementation defined". Without additional, non-standard
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arrangements, it is not possible to turn them into a useful tool.
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This example implementation chose to "not generate any of these signals,
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except as a result of explicit calls to the raise function", which is
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allowed by the standard but of course does nothing for the usefulness of
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<signal.h>.
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A useful signal handling would:
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1) make signal() a system call that registers the signal handler with the OS
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2) make raise() a system call triggering an OS signal to the running process
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3) make provisions that further signals of the same type are blocked until
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the signal handler returns (optional for SIGILL)
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*/
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/* These are the values used by Linux. */
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/* Abnormal termination / abort() */
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#define SIGABRT 6
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/* Arithmetic exception / division by zero / overflow */
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#define SIGFPE 8
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/* Illegal instruction */
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#define SIGILL 4
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/* Interactive attention signal */
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#define SIGINT 2
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/* Invalid memory access */
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#define SIGSEGV 11
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/* Termination request */
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#define SIGTERM 15
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/* The following should be defined to pointer values that could NEVER point to
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a valid signal handler function. (They are used as special arguments to
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signal().) Again, these are the values used by Linux.
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*/
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#define SIG_DFL (void (*)( int ))0
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#define SIG_ERR (void (*)( int ))-1
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#define SIG_IGN (void (*)( int ))1
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typedef _PDCLIB_sig_atomic_t sig_atomic_t;
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/* Installs a signal handler "func" for the given signal.
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A signal handler is a function that takes an integer as argument (the signal
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number) and returns void.
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Note that a signal handler can do very little else than:
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1) assign a value to a static object of type "volatile sig_atomic_t",
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2) call signal() with the value of sig equal to the signal received,
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3) call _Exit(),
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4) call abort().
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Virtually everything else is undefind.
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The signal() function returns the previous installed signal handler, which
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at program start may be SIG_DFL or SIG_ILL. (This implementation uses
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SIG_DFL for all handlers.) If the request cannot be honored, SIG_ERR is
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returned and errno is set to an unspecified positive value.
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*/
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_PDCLIB_PUBLIC void ( *signal( int sig, void ( *func )( int ) ) )( int );
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/* Raises the given signal (executing the registered signal handler with the
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given signal number as parameter).
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This implementation does not prevent further signals of the same time from
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occuring, but executes signal( sig, SIG_DFL ) before entering the signal
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handler (i.e., a second signal before the signal handler re-registers itself
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or SIG_IGN will end the program).
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Returns zero if successful, nonzero otherwise. */
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_PDCLIB_PUBLIC int raise( int sig );
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/* Extension hook for downstream projects that want to have non-standard
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extensions to standard headers.
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*/
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#ifdef _PDCLIB_EXTEND_SIGNAL_H
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#include _PDCLIB_EXTEND_SIGNAL_H
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#endif
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#endif
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