[PATCH] true,false: avoid initialization overhead unless needed

[Bernhard Voelker]

This is a minor performance improvement:

  $ strace -fv /bin/true --xxx 2>&1 | wc -l
  105

  $ strace -fv src/true --xxx 2>&1 | wc -l
  26

  $ time for i in $(seq 1000) ; do /bin/true --xxx ; done >/dev/null

  real  0m5.083s
  user  0m0.481s
  sys   0m4.319s

  $ time for i in $(seq 1000) ; do src/true --xxx ; done >/dev/null

  real  0m4.729s
  user  0m0.319s
  sys   0m4.107s


Do you think it's worth doing?

Have a nice day,
Berny


From 1c550664611f7e2557925898b1c896952675dbda Mon Sep 17 00:00:00 2001
From: Bernhard Voelker <address@hidden>
Date: Mon, 7 Jul 2014 10:31:46 +0200
Subject: [PATCH] true,false: avoid initialization overhead unless needed

* src/true.c (main): Instead of generally doing the common program
initialization when argc equals 2, only do it when one of the
--help or --version option is specified.
---
 src/true.c | 36 +++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/src/true.c b/src/true.c
index 8a1c4f9..0555721 100644
--- a/src/true.c
+++ b/src/true.c
@@ -58,22 +58,32 @@ main (int argc, char **argv)
      argument.  */
   if (argc == 2)
     {
-      initialize_main (&argc, &argv);
-      set_program_name (argv[0]);
-      setlocale (LC_ALL, "");
-      bindtextdomain (PACKAGE, LOCALEDIR);
-      textdomain (PACKAGE);
+      enum {NONE, H, V};
+      short opt = NONE;
+      if (STREQ (argv[1], "--help"))
+        opt = H;
+      else if (STREQ (argv[1], "--version"))
+        opt = V;

-      /* Note true(1) will return EXIT_FAILURE in the
-         edge case where writes fail with GNU specific options.  */
-      atexit (close_stdout);
+      if (opt != NONE)
+        {
+          initialize_main (&argc, &argv);
+          set_program_name (argv[0]);
+          setlocale (LC_ALL, "");
+          bindtextdomain (PACKAGE, LOCALEDIR);
+          textdomain (PACKAGE);

-      if (STREQ (argv[1], "--help"))
-        usage (EXIT_STATUS);
+          /* Note true(1) will return EXIT_FAILURE in the
+             edge case where writes fail with GNU specific options.  */
+          atexit (close_stdout);
+
+          if (opt == H)
+            usage (EXIT_STATUS);

-      if (STREQ (argv[1], "--version"))
-        version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,
-                     (char *) NULL);
+          if (opt == V)
+            version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,
+                         (char *) NULL);
+        }
     }

   exit (EXIT_STATUS);
--
1.8.4.2