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Re: pr-msvc-support: building .DLLs with symbols

From: Christopher Hulbert
Subject: Re: pr-msvc-support: building .DLLs with symbols
Date: Fri, 18 Sep 2009 06:16:51 -0400

On Fri, Sep 18, 2009 at 4:26 AM, Peter Rosin <address@hidden> wrote:
> Hi Ralf,
> Den 2009-09-18 06:37 skrev Ralf Wildenhues:
>> * Peter Rosin wrote on Thu, Sep 10, 2009 at 11:48:34AM CEST:
>>> Here's a couple of patches that implements support for -Wl, and
>>> -Xlinker for MSVC. The first one
>>> (rename-dashL_envvar-tolinker_envvar.patch)
>>> is just a rename, to reduce confusion,
>> In general, a rename from an ugly variable name like "dashL_envvar" is a
>> good thing.  However, it is also an API change that would normally need
>> announcing in NEWS and asking ourselves why we messed up before and had
>> to fix it.  Luckily, this one is in pr-msvc-support only, not in master,
>> so I don't have such a big problem with it.  However, if you do it then
>> please rename *all* instances of this ugliness (dashL_envvar_spec?).
>> With that, I think the first patch is probably a good thing.
> I didn't know dashL_envvar was considered so ugly. Noone told me since
> its introduction four years ago [1] so I was beginning to think that it
> was maybe ok, but I admit to not having given it much thought lately. I
> only changed it since the variable is now used for other things as well.

In my windows branch, I use link_search_path_spec as in:

_LT_TAGDECL([], [link_search_path_spec], [1],
    [Flag to add a directory to the linker search path])

Then, somewhere in the "-L*" case of argument processing in func_mode_link.

        if test -n "$link_search_path_spec"; then

where all cases of the existing "-L$dir" is replaced by
"$this_deplib". Note also that there is an explicit case for
"-LIBPATH:*" so that -LIBPATH can be used in user-defined environment
variables for example. My windows branch seems to work ok for the PGI
and Intel compilers on windows with a couple exceptions:

* running executables (e.g. test programs for the testsuite) that use DLLs.
* building DLLs with version information.


> [1]
> How should I name dashL_envvar_spec? For MSVC it is set to '-LIBPATH:'
> so that
> $ .../libtool --mode=link ... -L/foo/bar ...
> triggers a transformation into
> LINK=" -LIBPATH:C:/some/mount/foo/bar" cl ...
> So, linker_envvar is the name of the variable, and dashL_envvar_spec
> is what to prepend when moving -L paths to that variable. Should I
> just lose that variable altogether and hardcode the -LIBPATH: thing
> in func_to_linker_envvar (aka func_dashL_to_envvar)? It's not as if
> there are any other users of linker_envvar et al to consider at
> this point...
> Is dashl_xform also a bad name? It's a sed expression that transforms
> -lfoo into something more suitable (foo.lib in this case). Better
> suggestion welcome (if it is indeed distasteful, I wouldn't know).
>>> and the second patch
>>> (-Xlinker-msvc.patch) contains the new code...
>> And the @lt_linker@ thing is again so ugly it makes me cringe.
> Oops, sorry, I didn't mean to scare you :-)
>> No, really, I don't want to see code like this in master, that will be
>> unmaintainable a year down the road.  Why are we not looking for -Wl,
>> and transforming that if linker_envvar is nonempty?
> Because that would require $wl to be '-Wl,', which I thought was a bit
> misleading. But I can do it that way if that's preferred, please
> advise.
>>  And why does the
>> description of linker_envvar not state that it also holds other link
>> flags (is that maybe *not* true for some other systems on which this
>> variable is used)?
> After both these patches are applied, you have:
> @defvar linker_envvar
> When linking, move all paths specified with @option{-L} options to
> this variable, for toolchains where it makes sense to pass the library
> search paths in an environment variable. Linker options passed with
> @option{-Wl,} or @option{-Xlinker} may also be passed via this
> environment variable if @var{wl} is set to @samp{@@lt_envvar@@}.
> Normally disabled (i.e. @var{linker_envvar} empty).
> @end defvar
> So, I think you might have only picked up the rename of the variable
> and not the change in the description when its usage was actually
> changed in the second patch? Or?
>> Does the expanded form of $wl ever get into .la files BTW?  This would
>> certainly make them unusable for another compiler later on (this is not
>> something that is broken nor needs to be fixed with this patch, I'm just
>> noting it here because I see it and this is one of the few systems where
>> it makes a big difference.)
> No '-Wl,' options are added to neither inherited_linker_flags nor
> dependency_libs I think, so we're cool there. I think.
>>> Ok for the pr-msvc-support branch?
>> Well, to me that depends upon whether you want to rewrite this code for
>> an eventual inclusion in master anyway or not.
> I'm willing to do a rewrite if that's what it's going to take, but I
> prefer to do it before any "merge window" opens, and I need pointers on
> what needs to be rewritten. Just having the branch as a dumping spot
> for a pile of unacceptable patches is not much use.
>> Thanks, and sorry if that was a bit harsh,
> I can take the "heat", better harsh and timely than nothing at all...
> Cheers,
> Peter

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