>From 718f64eeeda938634fbdf14f99b33409376b7960 Mon Sep 17 00:00:00 2001
From: Peter Rosin <address@hidden>
Date: Tue, 11 Feb 2014 18:39:39 +0100
Subject: [PATCH] libtool: speed up lalib detection in execute mode

Execute mode is slow and might even DOS the computer in extreme
cases when a parameter is a big binary file without newlines.
Work around this by truncation if the dd utility is found and
working.

Fixes bug#13472 and bug#16662.

Reported by Pavel Raiskup and Nick Bowler.

* m4/libtool.m4 (_LT_CMD_TRUNCATE): New macro, for finding out
how to truncate pipes to 4k (fallback to no truncation if that
is not possible).
(_LT_SETUP): Require _LT_CMD_TRUNCATE.
* build_aux/ltmain.in (func_lalib_p): Truncate the pipe before
passing it on to sed.
* THANKS: Update.

Signed-off-by: Peter Rosin <address@hidden>
---
 THANKS              |    2 ++
 build-aux/ltmain.in |    2 +-
 m4/libtool.m4       |   22 ++++++++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletions(-)

diff --git a/THANKS b/THANKS
index e895aee..85c5150 100644
--- a/THANKS
+++ b/THANKS
@@ -150,6 +150,7 @@
   Mike Gorchak			address@hidden
   Mike Frysinger		address@hidden
   Mike Miller			address@hidden
+  Nick Bowler			address@hidden
   Nix				address@hidden
   Olaf Lenz			address@hidden
   Olly Betts			address@hidden
@@ -161,6 +162,7 @@
   Paul Eggert			address@hidden
   Paul Laight			address@hidden
   Paul Seidler			address@hidden
+  Pavel Raiskup			address@hidden
   Paweł Daniluk			address@hidden
   Peter Eisentraut		address@hidden
   Peter Fritzsche		address@hidden
diff --git a/build-aux/ltmain.in b/build-aux/ltmain.in
index 3b4e6ec..bff642e 100644
--- a/build-aux/ltmain.in
+++ b/build-aux/ltmain.in
@@ -577,7 +577,7 @@ _LTECHO_EOF'
 func_lalib_p ()
 {
     test -f "$1" &&
-      $SED -e 4q "$1" 2>/dev/null \
+      $lt_truncate_4k < "$1" 2>/dev/null | $SED -e 4q 2>/dev/null \
         | $GREP "^# Generated by .*$PACKAGE" > /dev/null 2>&1
 }
 
diff --git a/m4/libtool.m4 b/m4/libtool.m4
index ce58f31..d5967d2 100644
--- a/m4/libtool.m4
+++ b/m4/libtool.m4
@@ -169,6 +169,7 @@ m4_require([_LT_CHECK_SHAREDLIB_FROM_LINKLIB])dnl
 m4_require([_LT_CMD_OLD_ARCHIVE])dnl
 m4_require([_LT_CMD_GLOBAL_SYMBOLS])dnl
 m4_require([_LT_WITH_SYSROOT])dnl
+m4_require([_LT_CMD_TRUNCATE])dnl
 
 _LT_CONFIG_LIBTOOL_INIT([
 # See if we are running on zsh, and set the options that allow our
@@ -3216,6 +3217,27 @@ _LT_TAGDECL([], [reload_cmds], [2])dnl
 ])# _LT_CMD_RELOAD
 
 
+# _LT_CMD_TRUNCATE
+# ----------------
+# find command to truncate a pipe to 4k
+m4_defun([_LT_CMD_TRUNCATE],
+[AC_PATH_PROG([DD], [dd])
+test -z "$DD" && DD=dd
+
+AC_CACHE_CHECK([how to truncate pipes to 4k], [lt_cv_truncate_4k],
+[lt_cv_truncate_4k=cat
+printf 0123456789abcdef0123456789abcdef >conftest.i
+cat conftest.i conftest.i >conftest2.i
+if "$DD" bs=32 count=1 <conftest2.i >conftest.out 2>/dev/null; then
+  cmp -s conftest.i conftest.out && lt_cv_truncate_4k="$DD bs=4096 count=1"
+fi
+rm -f conftest.i conftest2.i conftest.out])
+
+_LT_DECL([lt_truncate_4k], [lt_cv_truncate_4k], [1],
+  [Command to truncate a pipe to 4k])
+])# _LT_CMD_TRUNCATE
+
+
 # _LT_CHECK_MAGIC_METHOD
 # ----------------------
 # how to check for library dependencies
-- 
1.7.9