libtool-2.0 release [WAS per-deplib static/dynamic flags]

[Gary V. Vaughan]

Hallo Ralf, Bob, Peter, Eric,

Is this patch really necessary for 2.0?  I think that introducing so
much code churn in to libtool at this stage is going to bring yet more
release delays.  Surely the feature is useful and desireable, but I
really *really* want to avoid more delays for 2.0.

Now is the time to branch!  Either a feature branch for developing the
per-deplib feature for merging after 2.0, or else a 2.0 branch that we
can keep stable.

My preference is to make a feature branch now, and not branch for 2.0
at least until the release blockers are resolved, so that we can commit
any bugfixes we discover during testing just once (we went through the
mess of porting to three branches during the last branch-2-0 debacle,
and I don't want to do that again!).

According to: http://tkd.kicks-ass.net/GnuLibtoolProject/RoadMap, the
three remaining release blockers for 2.0 are:

 * <!> libtool.m4 macro ordering/requirement audit. pending
 * <!> LT_WITH_LTDL should build libltdl by default; currently
       nothing happens unless LTDL_CONVENIENCE or LTDL_INSTALLABLE
       is also given.
 * <!> fix potential denial of service with compilers that do not
       understand "-c -o".
       * not very likely to happen
       * http://lists.gnu.org/archive/html/libtool-patches/2005-03/msg00252.html

And I would even dispute whether the first of those is really a release
blocker -- the code *does* need an audit, but it's been in that state for
several existing releases already.  lists.gnu.org and mail.gnu.org appear
to be down, so I can't read the post attached to the final blocker to
remind myself of that issue.

So here are the action points, initialed where I plan to take them
pending agreement from (most of) you guys.

 1. strike the macro ordering audit from the release blocker list.   GVV
 2. fix LTDL_{CONVENIENCE,INSTALLABLE} bug on CVS HEAD.              GVV
 3. make a per-deblib-branch for these changes.
 4. evaluate whether -c -o DoS is a release blocker too.
    4a. fix it if it is
    4b. strike it from the blocker list if it isn't
 5. test like crazy. and fix any platform issues uncovered           GVV
 6. release libtool-2.0 already!                                     GVV

Once 2.0 is finally out, I will take a back seat with libtool for a while
to work on m4-2.0 and my new book.

Ralf Wildenhues wrote:
> Hi Bob, Albert,
> 
> * Bob Friesenhahn wrote on Wed, Feb 01, 2006 at 07:47:51AM CET:
>> On Tue, 31 Jan 2006, Albert Chin wrote:
>>
>>> On Mon, Jan 30, 2006 at 10:28:52PM +0100, Ralf Wildenhues wrote:
>>>> - Should the corresponding libtool flags be named `-Bstatic' resp.
>>>>  `-Bdynamic'?  Those were the most common names I could find, but IMHO
>>>>  they are not very self-explanatory for users not used to them.
>>> -prefer-static, -prefer-dynamic/-prefer-shared? The -Bxxx doesn't seem
>>> similar with current libtool options.
>> At least for the static case, I would prefer the link to entirely fail 
>> if a static library is requested but one can not be found.  Usually 
>> there is a very important reason to use a static library if it has 
>> specifically been requested.  So the wording should not be 'prefer' 
>> for the static case.  I agree that the -B syntax does not fit the 
>> style of other libtool options (but does match many linkers).
> 
> Several different issues here:
> - the option naming, which I will not delve into in this post, and
> - whether what I'll call -Bstatic for now should fail if it does not
>   find a static library to link against.
> 
> The latter point is intricate, and requires much more elaboration to be
> completely specified.  That's the main reason I kept the semantics so
> vague in my proposal.  The issues are: library search algorithm,
> difference between libtool and non-libtool libraries, linker capability.
> 
> 1) The linker may not allow to specify per-deplib linkage at all, or may
> not have a flag to force static linkage (as opposed to only _prefer_ it).
> Examples for the former are Darwin; I haven't found an example for the
> latter yet (good!).  But this means, that for non-libtool libraries we
> cannot guarantee a certain linking mode, unless we were to change our
> search algorithm quite drastically (which I don't see as an option ATM).
> 
> 2) Difference between libtool libraries (*.la) and non-libtool ones, and
> libtool search algorithm and native linker search algorithm.
> 
> The current libtool library search algorithm looks a bit like this
> (before my patch):
> 
> - given `path/to/libfoo.la', that is taken and nothing else.
> - given `path/to/libfoo.a' ($libext), that is taken and nothing else.
> - given `-lfoo'
>     for all searchdirs that we look at,
>       for the extensions `.la', `$std_shrext', `.so', `.a'   [1]
>         check whether there exists a file libfoo.$extension
>           if yes, exit search algorithm
> 
> My patch skips `$std_shrext' and `.so' when in Bstatic mode, but it
> still happily picks the first `.la' file it can find, even iff that one
> was shared-only, for example.  Currently it then links shared or fails
> to link, depending on hardcoding features of the linker, and on whether
> the linker fails to link shared in Bstatic mode.  It may be more useful
> to either
> - fail outright if the first .la library wasn't good, or
> - go back and scan the rest of the searchdirs for a better candidate
>   library.
> But this would open new questions: would we then accept .la libraries as
> better candidates only, or also $libext archives?
> 
> 
> The same question already goes for `-static' and `-static-libtool-libs':
> Should they fail upon encounter of a disable-static libtool library?
> Obviously that is more of an issue for `-static-libtool-libs' because it
> also involves libraries not in the current package tree.
> 
> Now about non-libtool libaries: while I believe all linkers (that have
> Bstatic flags) will fail if they find a shared but no static library
> anywhere in the search path, this needs testing.  I will extend
> static.at to do this as well, but even then there's no guarantee another
> system may have this limitation.
> 
> Hope that helps a bit.
> 
> Cheers,
> Ralf
> 
> [1] we need to exchange `.a' with $libext, or add $libext if != `.a' for
>     w32 systems, I believe.

Cheers,
        Gary.
-- 
Gary V. Vaughan      ())_.  address@hidden,gnu.org}
Research Scientist   ( '/   http://tkd.kicks-ass.net
GNU Hacker           / )=   http://www.gnu.org/software/libtool
Technical Author   `(_~)_   http://sources.redhat.com/autobook

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