Import selfpipe code from skalibs 1.2.5

[andersk@mit.edu: Move code to new third/libstddjb directory]

third/libstddjb/selfpipe_untrap.c

@@ -0,0 +1,54 @@
+/* ISC license. */
+
+/* MT-unsafe */
+
+#include <errno.h>
+#include <signal.h>
+#include "sysdeps.h"
+#include "selfpipe-internal.h"
+#include "selfpipe.h"
+
+#ifdef HASSIGNALFD
+
+#include <sys/signalfd.h>
+
+int selfpipe_untrap (int sig)
+{
+  sigset_t ss = selfpipe_caught ;
+  sigset_t blah ;
+  register int r = sigismember(&selfpipe_caught, sig) ;
+  if (selfpipe_fd < 0) return (errno = EBADF, -1) ;
+  if (r < 0) return -1 ;
+  if (!r) return (errno = EINVAL, -1) ;
+  if ((sigdelset(&ss, sig) < 0)
+   || (signalfd(selfpipe_fd, &ss, SFD_NONBLOCK | SFD_CLOEXEC) < 0))
+    return -1 ;
+  sigemptyset(&blah) ;
+  sigaddset(&blah, sig) ;
+  if (sigprocmask(SIG_UNBLOCK, &blah, 0) < 0)
+  {
+    int e = errno ;
+    signalfd(selfpipe_fd, &selfpipe_caught, SFD_NONBLOCK | SFD_CLOEXEC) ;
+    errno = e ;
+    return -1 ;
+  }
+  selfpipe_caught = ss ;
+  return 0 ;
+}
+
+#else
+
+#include "sig.h"
+
+int selfpipe_untrap (int sig)
+{
+  register int r = sigismember(&selfpipe_caught, sig) ;
+  if (selfpipe_fd < 0) return (errno = EBADF, -1) ;
+  if (r < 0) return -1 ;
+  if (!r) return (errno = EINVAL, -1) ;
+  if (sig_restore(sig) < 0) return -1 ;
+  sigdelset(&selfpipe_caught, sig) ;
+  return 0 ;
+}
+
+#endif