hostid: improve extremely unreadable parts

*: remove checks of sigaction and sigprocmask results
 in cases where they clearly can't fail:
 sigaction(known_good_sig)
 sigprocmask(known_good_how)

    text           data     bss     dec     hex filename
-    393              4       0     397     18d libc/pwd_grp/lckpwdf.o
+    382              4       0     386     182 libc/pwd_grp/lckpwdf.o
-     56              0       0      56      38 libc/signal/sigblock.o
+     44              0       0      44      2c libc/signal/sigblock.o
-    211              0       0     211      d3 libc/signal/sigset.o
+    202              0       0     202      ca libc/signal/sigset.o
-     56              0       0      56      38 libc/signal/sigsetmask.o
+     44              0       0      44      2c libc/signal/sigsetmask.o
-    309              0       0     309     135 libc/unistd/sleep.o
+    256              0       0     256     100 libc/unistd/sleep.o

1 files changed, 3 insertions, 5 deletions

diff --git a/libc/signal/sigset.c b/libc/signal/sigset.c
index 91f433661..03f3dc869 100644
--- a/libc/signal/sigset.c
+++ b/libc/signal/sigset.c
@@ -42,13 +42,11 @@ __sighandler_t sigset (int sig, __sighandler_t disp)
   /* Handle SIG_HOLD first.  */
   if (disp == SIG_HOLD)
     {
-      /* Create an empty signal set.  */
       __sigemptyset (&set);
       __sigaddset (&set, sig);
 
       /* Add the signal set to the current signal mask.  */
-      if (sigprocmask (SIG_BLOCK, &set, NULL) < 0)
-	return SIG_ERR;
+      sigprocmask (SIG_BLOCK, &set, NULL); /* can't fail */
 
       return SIG_HOLD;
     }
@@ -56,6 +54,7 @@ __sighandler_t sigset (int sig, __sighandler_t disp)
 
   memset(&act, 0, sizeof(act));
   act.sa_handler = disp;
+  /* In Linux (as of 2.6.25), fails only if sig is SIGKILL or SIGSTOP */
   if (sigaction (sig, &act, &oact) < 0)
     return SIG_ERR;
 
@@ -64,8 +63,7 @@ __sighandler_t sigset (int sig, __sighandler_t disp)
   __sigaddset (&set, sig);
 
   /* Remove the signal set from the current signal mask.  */
-  if (sigprocmask (SIG_UNBLOCK, &set, NULL) < 0)
-    return SIG_ERR;
+  sigprocmask (SIG_UNBLOCK, &set, NULL); /* can't fail */
 
   return oact.sa_handler;
 }