top: at program startup, avoid a little extra overhead

There was a time when the PROCPS_PIDS_noop represented
the highest valued enumerator. Therefore if one wished
to prime an array consisting of pids_result structures
with this specific item a loop would have been needed.

Now that this enum is the first one, with the value of
zero, we can avoid avoid such a loop with just calloc.

But just in case, we'll use an 'if' to guarantee zero.

[ and the nice thing is, since the value is known at ]
[ compile time, that 'if' test plus subordinate loop ]
[ can be discarded by the compiler as long as it's 0 ]

Reference(s):
. <pids> introduced (PIDS_noop > 0)
commit 7e6a371d8a36b250a2edddff9f5d059640b8132e
. top employs PIDS_noop at 'new' time
commit f1bd82ff07d67dbcfa455e82678f44376cfe1a90
. <pids> relocated PIDS_noop (PIDS_noop == 0)
commit e7585992d9c0743246247b3d6ee0041942fe07d5

Signed-off-by: Jim Warner <james.warner@comcast.net>

diff --git a/top/top.c b/top/top.c
index d0fe2784f6036f3521072dc436cbcabc528e366e..b4b355ca9b9ff34c6880cde6063384568695cad7 100644 (file)
--- a/top/top.c
+++ b/top/top.c
@@ -2821,9 +2821,10 @@ static void before (char *me) {
 
    // establish max depth for newlib pids stack (# of result structs)
    Pids_itms = alloc_c(sizeof(enum pids_item) * MAXTBL(Fieldstab));
-   for (i = 0; i < MAXTBL(Fieldstab); i++)
-      Pids_itms[i] = PIDS_noop;
-   Pids_itms_cur = i;
+   if (PIDS_noop != 0)
+      for (i = 0; i < MAXTBL(Fieldstab); i++)
+         Pids_itms[i] = PIDS_noop;
+   Pids_itms_cur = MAXTBL(Fieldstab);
    // we will identify specific items in the build_headers() function
    if (procps_pids_new(&Pids_ctx, Pids_itms, Pids_itms_cur))
       error_exit(fmtmk(N_fmt(LIB_errorpid_fmt),__LINE__));