text: // Copyright 2018 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // +build freebsd,amd64
  
  #include <errno.h>
  #include <stddef.h>
  #include <stdint.h>
  #include <string.h>
  #include <signal.h>
  
  #include "libcgo.h"
  
  // go_sigaction_t is a C version of the sigactiont struct from
  // os_freebsd.go.  This definition — and its conversion to and from struct
  // sigaction — are specific to freebsd/amd64.
  typedef struct {
          uint32_t __bits[_SIG_WORDS];
  } go_sigset_t;
  typedef struct {
  	uintptr_t handler;
  	int32_t flags;
  	go_sigset_t mask;
  } go_sigaction_t;
  
  int32_t
  x_cgo_sigaction(intptr_t signum, const go_sigaction_t *goact, go_sigaction_t *oldgoact) {
  	int32_t ret;
  	struct sigaction act;
  	struct sigaction oldact;
  	int i;
  
  	_cgo_tsan_acquire();
  
  	memset(&act, 0, sizeof act);
  	memset(&oldact, 0, sizeof oldact);
  
  	if (goact) {
  		if (goact->flags & SA_SIGINFO) {
  			act.sa_sigaction = (void(*)(int, siginfo_t*, void*))(goact->handler);
  		} else {
  			act.sa_handler = (void(*)(int))(goact->handler);
  		}
  		sigemptyset(&act.sa_mask);
  		for (i = 0; i < 8 * sizeof(goact->mask); i++) {
  			if (goact->mask.__bits[i/32] & ((uint32_t)(1)<<(i&31))) {
  				sigaddset(&act.sa_mask, i+1);
  			}
  		}
  		act.sa_flags = goact->flags;
  	}
  
  	ret = sigaction(signum, goact ? &act : NULL, oldgoact ? &oldact : NULL);
  	if (ret == -1) {
  		// runtime.sigaction expects _cgo_sigaction to return errno on error.
  		_cgo_tsan_release();
  		return errno;
  	}
  
  	if (oldgoact) {
  		if (oldact.sa_flags & SA_SIGINFO) {
  			oldgoact->handler = (uintptr_t)(oldact.sa_sigaction);
  		} else {
  			oldgoact->handler = (uintptr_t)(oldact.sa_handler);
  		}
  		for (i = 0 ; i < _SIG_WORDS; i++) {
  			oldgoact->mask.__bits[i] = 0;
  		}
  		for (i = 0; i < 8 * sizeof(oldgoact->mask); i++) {
  			if (sigismember(&oldact.sa_mask, i+1) == 1) {
  				oldgoact->mask.__bits[i/32] |= (uint32_t)(1)<<(i&31);
  			}
  		}
  		oldgoact->flags = oldact.sa_flags;
  	}
  
  	_cgo_tsan_release();
  	return ret;
  }
  