From e666896b70d518934690fe2c6ad4dd75f73a0c65 Mon Sep 17 00:00:00 2001
From: "Kyle J. McKay" <mackyle@gmail.com>
Date: Fri, 24 Apr 2015 15:34:44 -0700
Subject: [PATCH] shlib.sh: provide xargs wrapper to compensate for broken
 behavior

On some platforms running the following:

  xargs </dev/null echo broken

outputs "broken" instead of nothing.  So if you're feeding the command
a list of file names to operate on as output by find, it gets run with
no arguments at all even if nothing is found.

This is very bad.

Supply an xargs() wrapper function in shlib.sh that automatically
provides the correct option on broken platforms that need it in
order to suppress this broken behavior and correctly not run the
utility at all if there are no incoming arguments to xargs.

Note that conveniently we can use xargs itself to diagnose this
problem by running:

  : | xargs echo -r

Which will output '-r' on platforms that need it to fix the
broken behavior.  We just do this once and save the result
in the var_xargs_r variable.

And now that we have the wrapper in place, we remove the kludge
from the xargs line in install.sh since it's no longer necessary.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
---
 install.sh | 2 +-
 shlib.sh   | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/install.sh b/install.sh
index bc5628e..3b8de02 100755
--- a/install.sh
+++ b/install.sh
@@ -178,7 +178,7 @@ fi
 chown_make() {
 	if [ "$LOGNAME" = root -a -n "$SUDO_USER" -a "$SUDO_USER" != root ]; then
 		find "$@" -user root -print0 2>/dev/null | \
-		xargs $(: | xargs echo -r) -0 chown "$SUDO_USER:$(id -gn "$SUDO_USER")"
+		xargs -0 chown "$SUDO_USER:$(id -gn "$SUDO_USER")"
 	elif [ "$LOGNAME" = root -a -z "$SUDO_USER" -o "$SUDO_USER" = root ]; then
 		echo "*** WARNING: running make as root w/o sudo may leave root-owned: $*"
 	fi
diff --git a/shlib.sh b/shlib.sh
index 8ecfde3..a8eb512 100644
--- a/shlib.sh
+++ b/shlib.sh
@@ -64,6 +64,7 @@ get_girocco_config_var_list() (
 	# var_window_memory	Value to use for repack --window-memory=
 	# var_log_window_size	Value to use for git-svn --log-window-size=
 	# var_utf8_locale	Value to use for a UTF-8 locale if available
+	# var_xargs_r		A "-r" if xargs needs it to behave correctly
 	_cfg_vars="$(get_girocco_config_pm_var_list)"
 	eval "$_cfg_vars"
 	printf '%s\n' "$_cfg_vars"
@@ -84,6 +85,8 @@ get_girocco_config_var_list() (
 		sed -e '/en_US/ s/^/0 /; /en_US/ !s/^/1 /' | LC_ALL=C sort | \
 		head -n 1 | cut -d ' ' -f 2)"
 	[ -z "$_guess_locale" ] || printf 'var_utf8_locale=%s.UTF-8\n' "$_guess_locale"
+	# On some broken platforms running xargs without -r and empty input runs the command
+	printf 'var_xargs_r=%s\n' "$(: | command xargs echo -r)"
 )
 
 # If basedir has been replaced, and shlib_vars.sh exists, get the config
@@ -154,6 +157,11 @@ git() (
 
 nc_openbsd() { "$cfg_nc_openbsd_bin" "$@"; }
 
+# Some platforms' broken xargs runs the command always at least once even if
+# there's no input unless given a special option.  Automatically supply the
+# option on those platforms by providing an xargs function.
+xargs() { command xargs $var_xargs_r "$@"; }
+
 _addrlist() {
 	_list=
 	for _addr in "$@"; do
-- 
2.11.4.GIT