[PATCH] sln: Install as a hard link to ldconfig

[fweimer at redhat dot com (Florian Weimer)]

Implementing and sln and ldconfig with the same binary saves
around 850 KiB from a glibc installation.

The sln program is implicitly tested during the build, so no test
case is needed.

2016-07-13  Florian Weimer  <fweimer@redhat.com>

	Use the same binary for ldconfig and sln.
	* elf/sln.h: New file.
	* elf/sln.c (run_sln): New function.
	(PACKAGE): Remove.
	(sln_main): Renamed from main.
	* elf/ldconfig.c (main): Call sln_main if run_sln.
	* elf/Makefile (others): Remove sln.
	(others-static, install-rootsbin, sln-modules, extra-objs): Remove.
	(ldconfig-modules): Add sln.
	(install-others-programs): Likewise.
	(sln): Create as hard link to ldconfig.
	(/sbin/sln): Create as hard link to /sbin/ldconfig.

diff --git a/elf/Makefile b/elf/Makefile
index 593403c..38ef328 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -70,12 +70,8 @@ install-others	= $(inst_rtlddir)/$(rtld-installed-name)
 install-bin-script = ldd
 endif
 
-others		= sprof sln
+others		= sprof
 install-bin	= sprof
-others-static   = sln
-install-rootsbin = sln
-sln-modules	:= static-stubs
-extra-objs	+= $(sln-modules:=.o)
 
 ifeq (yes,$(use-ldconfig))
 ifeq (yes,$(build-shared))
@@ -83,8 +79,15 @@ others-static	+= ldconfig
 others		+= ldconfig
 install-rootsbin += ldconfig
 
-ldconfig-modules := cache readlib xmalloc xstrdup chroot_canon static-stubs
+ldconfig-modules := cache readlib xmalloc xstrdup chroot_canon static-stubs sln
 extra-objs	+= $(ldconfig-modules:=.o)
+
+# Install sln as a hard link to ldconfig.
+install-others-programs += $(inst_rootsbindir)/sln
+$(objpfx)sln: $(objpfx)ldconfig
+	ln -f $< $@
+$(inst_rootsbindir)/sln: $(inst_rootsbindir)/ldconfig
+	ln -f $< $@
 endif
 endif
 
@@ -466,8 +469,6 @@ $(objpfx)ldd: ldd.bash.in $(common-objpfx)soversions.mk \
 
 $(objpfx)sprof: $(libdl)
 
-$(objpfx)sln: $(sln-modules:%=$(objpfx)%.o)
-
 $(objpfx)ldconfig: $(ldconfig-modules:%=$(objpfx)%.o)
 
 SYSCONF-FLAGS := -D'SYSCONFDIR="$(sysconfdir)"'
diff --git a/elf/ldconfig.c b/elf/ldconfig.c
index 467ca82..972737c 100644
--- a/elf/ldconfig.c
+++ b/elf/ldconfig.c
@@ -44,6 +44,8 @@
 
 #include <dl-procinfo.h>
 
+#include "sln.h"
+
 #ifdef _DL_FIRST_PLATFORM
 # define _DL_FIRST_EXTRA (_DL_FIRST_PLATFORM + _DL_PLATFORMS_COUNT)
 #else
@@ -1275,6 +1277,9 @@ main (int argc, char **argv)
   /* Set the text message domain.  */
   textdomain (_libc_intl_domainname);
 
+  if (run_sln (argv[0]))
+    return sln_main (argc, argv);
+
   /* Parse and process arguments.  */
   int remaining;
   argp_parse (&argp, argc, argv, 0, &remaining, NULL);
diff --git a/elf/sln.c b/elf/sln.c
index fa4ccec..c6889d7 100644
--- a/elf/sln.c
+++ b/elf/sln.c
@@ -1,4 +1,4 @@
-/* `sln' program to create symbolic links between files.
+/* sln helper to create symbolic links between files, invoked from ldconfig.
    Copyright (C) 1998-2016 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -31,21 +31,29 @@
 
 #include "../version.h"
 
-#define PACKAGE _libc_intl_domainname
+#include "sln.h"
 
 static int makesymlink (const char *src, const char *dest);
 static int makesymlinks (const char *file);
 static void usage (void);
 
+/* Check if we have to run sln.  */
+bool
+run_sln (const char *argv0)
+{
+  const char *slash = strrchr (argv0, '/');
+  const char *progname;
+  if (slash == NULL)
+    progname = argv0;
+  else
+    progname = slash + 1;
+  return strcmp (progname, "sln") == 0;
+}
+
+/* Invoked from ldconfig.  */
 int
-main (int argc, char **argv)
+sln_main (int argc, char **argv)
 {
-  /* Set locale via LC_ALL.  */
-  setlocale (LC_ALL, "");
-
-  /* Set the text message domain.  */
-  textdomain (PACKAGE);
-
   switch (argc)
     {
     case 2:
diff --git a/elf/sln.h b/elf/sln.h
new file mode 100644
index 0000000..a3a16ab
--- /dev/null
+++ b/elf/sln.h
@@ -0,0 +1,30 @@
+/* Interface of the sln command-line tool.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef SLN_H
+#define SLN_H
+
+#include <stdbool.h>
+
+/* Return true if main should invoke sln_main.  */
+bool run_sln (const char *argv0);
+
+/* Main routine of the sln command.  */
+int sln_main (int argc, char **argv);
+
+#endif  /* SLN_H */