Trailing-Edge
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PDP-10 Archives
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SRI_NIC_PERM_FS_1_19910112
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kcc-6/lib/usys/signal.c
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/*
** SIGNAL - Simulate 4.3BSD signal mechanism, via sigvec()
**
** (c) Copyright Ken Harrenstien 1989
** for all changes after v.2, 16-Aug-1987
** (c) Copyright Ken Harrenstien, SRI International 1987
**
** See the file SIGNAL.DOC for more background information on this code.
*/
#include <c-env.h>
#include <errno.h>
#include <signal.h>
#include <sys/usysig.h> /* USYS_ macros */
extern int sigvec(); /* Syscall */
#if __STDC__
typedef void (*hndlr_t)(int); /* Type of sv_handler (for convenience) */
#else
typedef void (*hndlr_t)();
#endif
hndlr_t
signal(sig, func)
int sig;
hndlr_t func;
{
struct sigvec sv;
hndlr_t ofunc;
USYS_BEG();
if (sigvec(sig, (struct sigvec *)0, &sv) != 0) /* Get old sigvec */
USYS_RET(SIG_ERR); /* errno already set to EINVAL by sigvec() */
ofunc = sv.sv_handler; /* Remember old handler */
sv.sv_handler = func; /* Set up new sigvec for this signal */
if (sigvec(sig, &sv, (struct sigvec *)0) != 0) /* Set new sigvec */
USYS_RET(SIG_ERR);
USYS_RET(ofunc); /* Won, return previous handler */
}