getloadavg: set errno

* lib/getloadavg.c: Set errno when returning -1.  If no other
error number looks appropriate, set it to ENOSYS if the getloadavg
looks like it can't possibly ever work, ENOTSUP otherwise.
Suggested by Bruno Haible in
<http://lists.gnu.org/archive/html/bug-gnulib/2011-02/msg00187.html>.

getloadavg: trim unused parts and speed up 'configure'
* NEWS: Document this.
* lib/getloadavg.c: Ignore HAVE_GETLOADAVG; this file is now
always compiled if getloadavg is absent.
Move test code to ...
* tests/test-getloadavg.c: New file, containing previous
contents of test from lib/getloadavg.c.  It also contains
suggestions by Bruno Haible in
<http://lists.gnu.org/archive/html/bug-gnulib/2011-02/msg00186.html>.
* modules/getloadavg-tests: New file.
* m4/getloadavg.m4 (gl_GETLOADAVG): Do not check for getloadavg twice.
Do tests in the same order as they're needed for getloadavg.c.
Omit setgid-related tests that generate symbols KMEM_GROUP,
NEET_SETGID, GETLOADAVG_PRIVILEGED; nobody seems to use those any more.
Do only the tests that are needed to see whether the system has
getloadavg, moving the other tests into ...
(gl_PREREQ_GETLOADAVG): ... here.  Do not define obsolete symbol
NLIST_NAME_UNION; nobody should be using it.  Do not define
symbols C_GETLOADAVG and HAVE_GETLOADAVG; they're no longer
relevant, as the user of this module shouldn't care how getloadavg
is implemented.

1 files changed, 29 insertions, 59 deletions

diff --git a/lib/getloadavg.c b/lib/getloadavg.c
index 29c9bfff00..28e2ea0164 100644
--- a/lib/getloadavg.c
+++ b/lib/getloadavg.c
@@ -94,11 +94,6 @@
 #include <errno.h>
 #include <stdio.h>
 
-/* Exclude all the code except the test program at the end
-   if the system has its own `getloadavg' function.  */
-
-#ifndef HAVE_GETLOADAVG
-
 # include <sys/types.h>
 
 /* Both the Emacs and non-Emacs sections want this.  Some
@@ -500,7 +495,7 @@ static kvm_t *kd;
 /* Put the 1 minute, 5 minute and 15 minute load averages
    into the first NELEM elements of LOADAVG.
    Return the number written (never more than 3, but may be less than NELEM),
-   or -1 if an error occurred.  */
+   or -1 (setting errno) if an error occurred.  */
 
 int
 getloadavg (double loadavg[], int nelem)
@@ -509,9 +504,7 @@ getloadavg (double loadavg[], int nelem)
 
 # ifdef NO_GET_LOAD_AVG
 #  define LDAV_DONE
-  /* Set errno to zero to indicate that there was no particular error;
-     this function just can't work at all on this system.  */
-  errno = 0;
+  errno = ENOSYS;
   elem = -1;
 # endif
 
@@ -521,6 +514,7 @@ getloadavg (double loadavg[], int nelem)
   kstat_ctl_t *kc;
   kstat_t *ksp;
   kstat_named_t *kn;
+  int saved_errno;
 
   kc = kstat_open ();
   if (kc == 0)
@@ -559,7 +553,9 @@ getloadavg (double loadavg[], int nelem)
         }
     }
 
+  saved_errno = errno;
   kstat_close (kc);
+  errno = saved_errno;
 # endif /* HAVE_LIBKSTAT */
 
 # if !defined (LDAV_DONE) && defined (hpux) && defined (HAVE_PSTAT_GETDYNAMIC)
@@ -605,13 +601,15 @@ getloadavg (double loadavg[], int nelem)
 
   char ldavgbuf[3 * (INT_STRLEN_BOUND (int) + sizeof ".00 ")];
   char const *ptr = ldavgbuf;
-  int fd, count;
+  int fd, count, saved_errno;
 
   fd = open (LINUX_LDAV_FILE, O_RDONLY);
   if (fd == -1)
     return -1;
   count = read (fd, ldavgbuf, sizeof ldavgbuf - 1);
+  saved_errno = errno;
   (void) close (fd);
+  errno = saved_errno;
   if (count <= 0)
     return -1;
   ldavgbuf[count] = '\0';
@@ -629,7 +627,10 @@ getloadavg (double loadavg[], int nelem)
       if (! ('0' <= *ptr && *ptr <= '9'))
         {
           if (elem == 0)
-            return -1;
+            {
+              errno = ENOTSUP;
+              return -1;
+            }
           break;
         }
 
@@ -667,7 +668,10 @@ getloadavg (double loadavg[], int nelem)
                   &scale);
   (void) fclose (fp);
   if (count != 4)
-    return -1;
+    {
+      errno = ENOTSUP;
+      return -1;
+    }
 
   for (elem = 0; elem < nelem; elem++)
     loadavg[elem] = (double) load_ave[elem] / (double) scale;
@@ -708,7 +712,10 @@ getloadavg (double loadavg[], int nelem)
     }
 
   if (!getloadavg_initialized)
-    return -1;
+    {
+      errno = ENOTSUP;
+      return -1;
+    }
 # endif /* NeXT */
 
 # if !defined (LDAV_DONE) && defined (UMAX)
@@ -893,7 +900,10 @@ getloadavg (double loadavg[], int nelem)
     }
 
   if (!getloadavg_initialized)
-    return -1;
+    {
+      errno = ENOTSUP;
+      return -1;
+    }
 # endif /* ! defined LDAV_DONE && defined __VMS */
 
 # if ! defined LDAV_DONE && defined LOAD_AVE_TYPE && ! defined __VMS
@@ -1009,7 +1019,10 @@ getloadavg (double loadavg[], int nelem)
     }
 
   if (offset == 0 || !getloadavg_initialized)
-    return -1;
+    {
+      errno = ENOTSUP;
+      return -1;
+    }
 # endif /* ! defined LDAV_DONE && defined LOAD_AVE_TYPE && ! defined __VMS */
 
 # if !defined (LDAV_DONE) && defined (LOAD_AVE_TYPE) /* Including VMS.  */
@@ -1024,51 +1037,8 @@ getloadavg (double loadavg[], int nelem)
 # endif /* !LDAV_DONE && LOAD_AVE_TYPE */
 
 # if !defined LDAV_DONE
-  /* Set errno to zero to indicate that there was no particular error;
-     this function just can't work at all on this system.  */
-  errno = 0;
+  errno = ENOSYS;
   elem = -1;
 # endif
   return elem;
 }
-
-#endif /* ! HAVE_GETLOADAVG */
-
-#ifdef TEST
-int
-main (int argc, char **argv)
-{
-  int naptime = 0;
-
-  if (argc > 1)
-    naptime = atoi (argv[1]);
-
-  while (1)
-    {
-      double avg[3];
-      int loads;
-
-      errno = 0;                /* Don't be misled if it doesn't set errno.  */
-      loads = getloadavg (avg, 3);
-      if (loads == -1)
-        {
-          perror ("Error getting load average");
-          return EXIT_FAILURE;
-        }
-      if (loads > 0)
-        printf ("1-minute: %f  ", avg[0]);
-      if (loads > 1)
-        printf ("5-minute: %f  ", avg[1]);
-      if (loads > 2)
-        printf ("15-minute: %f  ", avg[2]);
-      if (loads > 0)
-        putchar ('\n');
-
-      if (naptime == 0)
-        break;
-      sleep (naptime);
-    }
-
-  return EXIT_SUCCESS;
-}
-#endif /* TEST */