Preserve ordering of GNU ld library grouping flags

[Thomas Jahns]

Hello,








The attached patch is vs. the master branch of

which I hope is the correct place to use.

Regards, Thomas

From 01fe8e27da2cbebfe2db79606e7bb846554a6863 Mon Sep 17 00:00:00 2001
From: Thomas Jahns <ja...@dkrz.de>
Date: Mon, 31 Oct 2016 11:08:43 +0100
Subject: [PATCH] Fix handling of flags for GNU ld library grouping.

* -Wl,--start-group -Wl,--end-group -Wl,-\( -Wl,-) must preserve their
  respective position within the list of libraries to work as expected.
---
 build-aux/ltmain.in | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/build-aux/ltmain.in b/build-aux/ltmain.in
index 4cd3818..41e95d9 100644
--- a/build-aux/ltmain.in
+++ b/build-aux/ltmain.in
@@ -5324,6 +5324,11 @@ func_mode_link ()
 	arg=$func_stripname_result
 	;;
 
+      -Wl,--start-group|-Wl,--end-group|-Wl,-\(|-Wl,-\))
+	func_append deplibs " $arg"
+	continue
+	;;
+
       -Wl,*)
 	func_stripname '-Wl,' '' "$arg"
 	args=$func_stripname_result
@@ -5938,6 +5943,15 @@ func_mode_link ()
 	  alldeplibs=:
 	  continue
 	  ;;
+        -Wl,--start-group|-Wl,--end-group|-Wl,-\(|-Wl,-\))
+	  if test "$linkmode,$pass" = "prog,link"; then
+	    compile_deplibs="$deplib $compile_deplibs"
+	    finalize_deplibs="$deplib $finalize_deplibs"
+	  else
+	    deplibs="$deplib $deplibs"
+	  fi
+	  continue
+	  ;;
 	esac # case $deplib
 
 	$found || test -f "$lib" \
-- 
2.7.0.79.gdc08a19

I noticed that libtool unfortunately puts -Wl,--start-group -Wl,--end-group and their short-hands -Wl,-( and -Wl,-) into an early position in the argument list of the link command instead of the libraries they are meant to go with, i.e. as originally specified. Having libraries with cyclic dependencies is nothing I advocate for, but I think projects using libtool should be able to support it in their dependencies if necessary for external reasons. So I had a look at what ltmain.sh does and figured out what special handling was needed. The corresponding patch is quite simple and straigh-forward. So I hope it can be included with an upcoming release. git://git.savannah.gnu.org/libtool.git at commit 08c5524fb24b923ad91c2bdca836f1eafa56fd6c

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