[PATCH] Ensure LT_PATH_LD works when called before LT_INIT

[Charles Wilson]

* libltdl/m4/libtool.m4 (LT_PATH_LD): AC_REQUIRE _LT_PROG_ECHO_BACKSLASH.

Original patch by Yaakov Selkowitz. As he explained:
> 
> There's a bug in LT_PATH_LD (AC_PROG_LD) when called prior to LT_INIT 
> (AC_PROG_LIBTOOL):
> 
> checking for ld used by gcc... 
> /usr/lib/gcc/i686-pc-cygwin/4.3.2/../../../../i686-pc-cygwin/bin/ld: no input 
> files
> ./configure: line 3955: : command not found
> 
> Yet this does not occur when the same macro is run by LT_INIT.
> 
> Here's the offending hunk:
> 
>       # Canonicalize the pathname of ld
>       ac_prog=`$ECHO "$ac_prog"| $SED 's%\\\\%/%g'`
>       while $ECHO "$ac_prog" | $GREP "$re_direlt" > /dev/null 2>&1; do
>         ac_prog=`$ECHO $ac_prog| $SED "s%$re_direlt%/%"`
>       done
> 
> The problem is that $ECHO hasn't been defined yet.  This is done by
> _LT_PROG_ECHO_BACKSLASH, which is called at the beginning of LT_INIT, but 
> isn't
> an explicit requirement of LT_PATH_LD, which may be called on its own.
> (AFAICS, all other macros which use $ECHO are libtool-internal and would only
> be called after LT_INIT.)

While it is not typical for LT_* functions to be called before LT_INIT,
this can happen in this case because when libtool is in use, AC_PROG_LD
is AU_DEFUN'ed to _LT_PATH_LD.  And it is certainly ok for AC_PROG_LD
to be called before LT_INIT or AC_PROG_LIBTOOL (as AC_PROG_LIBTOOL is
AU_DEFUN'ed to LT_INIT).  So, it /ought/ to work, but it doesn't.

This patch seems like an obvious fix to me. Ok to push?

---
 libltdl/m4/libtool.m4 |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/libltdl/m4/libtool.m4 b/libltdl/m4/libtool.m4
index 5f24fab..6beb125 100644
--- a/libltdl/m4/libtool.m4
+++ b/libltdl/m4/libtool.m4
@@ -2772,6 +2772,7 @@ AC_REQUIRE([AC_CANONICAL_HOST])dnl
 AC_REQUIRE([AC_CANONICAL_BUILD])dnl
 m4_require([_LT_DECL_SED])dnl
 m4_require([_LT_DECL_EGREP])dnl
+m4_require([_LT_PROG_ECHO_BACKSLASH])dnl
 
 AC_ARG_WITH([gnu-ld],
     [AS_HELP_STRING([--with-gnu-ld],
-- 
1.6.3.1