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

8 files changed, 11 insertions, 10 deletions

diff --git a/libc/signal/sigblock.c b/libc/signal/sigblock.c
index 72b42c45e..5a16f336b 100644
--- a/libc/signal/sigblock.c
+++ b/libc/signal/sigblock.c
@@ -32,8 +32,7 @@ int sigblock (int mask)
   sigset_t set, oset;
 
   sigset_set_old_mask (&set, mask);
-  if (sigprocmask (SIG_BLOCK, &set, &oset) < 0)
-    return -1;
+  sigprocmask (SIG_BLOCK, &set, &oset); /* can't fail */
   return sigset_get_old_mask (&oset);
 }
 libc_hidden_def(sigblock)
diff --git a/libc/signal/sigintr.c b/libc/signal/sigintr.c
index 23f87e199..1a8d60eb2 100644
--- a/libc/signal/sigintr.c
+++ b/libc/signal/sigintr.c
@@ -34,6 +34,7 @@ int siginterrupt (int sig, int interrupt)
 #ifdef	SA_RESTART
   struct sigaction action;
 
+  /* Fails if sig is bad.  */
   if (sigaction (sig, NULL, &action) < 0)
     return -1;
 
diff --git a/libc/signal/sigjmp.c b/libc/signal/sigjmp.c
index d83b49a0b..646949935 100644
--- a/libc/signal/sigjmp.c
+++ b/libc/signal/sigjmp.c
@@ -31,7 +31,7 @@ int __sigjmp_save (sigjmp_buf env, int savemask) attribute_hidden;
 int __sigjmp_save (sigjmp_buf env, int savemask)
 {
     env[0].__mask_was_saved = (savemask &&
-	    sigprocmask (SIG_BLOCK, (sigset_t *) NULL, &env[0].__saved_mask) == 0);
+	    sigprocmask (SIG_BLOCK, NULL, &env[0].__saved_mask) == 0);
 
     return 0;
 }
diff --git a/libc/signal/signal.c b/libc/signal/signal.c
index 0ed281ab1..f3dfa33fc 100644
--- a/libc/signal/signal.c
+++ b/libc/signal/signal.c
@@ -45,6 +45,7 @@ __bsd_signal (int sig, __sighandler_t handler)
   __sigemptyset (&act.sa_mask);
   __sigaddset (&act.sa_mask, sig);
   act.sa_flags = __sigismember (&_sigintr, sig) ? 0 : SA_RESTART;
+  /* In Linux (as of 2.6.25), fails only if sig is SIGKILL or SIGSTOP */
   if (sigaction (sig, &act, &oact) < 0)
     return SIG_ERR;
 
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;
 }
diff --git a/libc/signal/sigsetmask.c b/libc/signal/sigsetmask.c
index 9349deb38..f8784e288 100644
--- a/libc/signal/sigsetmask.c
+++ b/libc/signal/sigsetmask.c
@@ -33,8 +33,7 @@ sigsetmask (int mask)
   sigset_t set, oset;
 
   sigset_set_old_mask (&set, mask);
-  if (sigprocmask (SIG_SETMASK, &set, &oset) < 0)
-    return -1;
+  sigprocmask (SIG_SETMASK, &set, &oset); /* can't fail */
   return sigset_get_old_mask (&oset);
 }
 libc_hidden_def(sigsetmask)
diff --git a/libc/signal/sigwait.c b/libc/signal/sigwait.c
index 64a889f7b..bed7f979a 100644
--- a/libc/signal/sigwait.c
+++ b/libc/signal/sigwait.c
@@ -74,6 +74,8 @@ int __sigwait (const sigset_t *set, int *sig)
         __sigdelset (&tmp_mask, this);
 
         /* Register temporary action handler.  */
+        /* In Linux (as of 2.6.25), fails only if sig is SIGKILL or SIGSTOP */
+        /* (so, will it work correctly if set has, say, SIGSTOP?) */
         if (sigaction (this, &action, &saved[this]) != 0)
           goto restore_handler;
       }
diff --git a/libc/signal/sysv_signal.c b/libc/signal/sysv_signal.c
index f573482f9..118094b27 100644
--- a/libc/signal/sysv_signal.c
+++ b/libc/signal/sysv_signal.c
@@ -49,6 +49,7 @@ __sighandler_t __sysv_signal (int sig, __sighandler_t handler)
   act.sa_handler = handler;
   __sigemptyset (&act.sa_mask);
   act.sa_flags = (SA_ONESHOT | SA_NOMASK | SA_INTERRUPT) & ~SA_RESTART;
+  /* In Linux (as of 2.6.25), fails only if sig is SIGKILL or SIGSTOP */
   if (sigaction (sig, &act, &oact) < 0)
     return SIG_ERR;