relink command needs --tag

[Charles Wilson]

I'm not sure exactly where in libtool to put this, so I can't provide a 
patch.  However, see the attached testcase...

This testcase -- and the original problem -- were discovered on a cygwin 
system (so you'll see references to .dll's) but the problem should also 
occur on linux/etc.

I stumbled on this problem trying to build ncurses with the newly-added 
libtool support.  Ncurses uses the system libtool script and does NOT 
build its own copy.  Further, ncurses does NOT use automake; rather it 
uses autoconf and hand-tooled Makefile.in's.

The issue crops up because:
  1) the system libtool "knows" that CXX should be g++
  2) ncurses configury detects CXX as c++ (because old-style 
autoconf-2.13 searches in this order: c++ g++ ...., but new-style 
autoconf-2.57, used to build the system libtool, searches for g++ first.)

So, you end up with a compile command of "/usr/bin/libtool c++ ..." but 
where the default compiler (as far as libtool is concerned) for C++ code 
is 'g++'.  In this circumstance, libtool requires the --tag=CXX flag.

That's fine; the hand-tooled Makefile.in's ensure that libtool gets what 
it wants.  The problem is, when doing 'make install' the C++ library is 
relinked, and thus the relink_cmd is triggered.

And the relink_cmd does NOT contain --tag=CXX, even tho the original 
command that linked the uninstalled library in the first place DID have 
--tag=CXX.  And so it breaks.

Somehow, the relink_cmd that is stored in the uninstalled la file must 
propogate the --tag argument (if any) -- but it doesn't.

You can see this by unpacking the attached test case.  It is a bit 
contrived, and does some "bad" automake things -- but I needed to do 
that in order to make the test case self-contained.  My test case does 
not use 'your' system libtool -- but demonstrates the same problem I 
found with ncurses+systemlibtool.

After unpacking the testcase, run the bootstrap script.  Then, configure 
as usual.  Next, do:

'make CXX=c++'

This works fine -- and you'll see that C++ files are compiled and linked 
using --tag=CXX.  (I assume that on 'your' system, you have both g++ and 
c++ [where c++ could be a symlink to g++], and that autoconf is 2.57 or 
above.  That way, the libtool thus constructed will believe that g++ is 
the default compiler thanks to the autoconf-2.57 compiler search order.)

Now, inspect the cxx/libcxxdll.la file -- you'll see that the relink_cmd 
variable does NOT contain --tag.

Finally, do:

'make install DESTDIR=/tmp'

The install fails, because of the missing --tag.

Can someone smarter than me please fix this, so that --tag=XXXX is 
included in relink_cmd whenever it is passed on the original --mode=link 
command line?

--
Chuck

no-tag-demo.tar.bz2
Description: BZip2 compressed data