Re: RFC: Building a Shared Library (take 2)

[Norman Gray]

Alexandre, greetings,

On Wednesday, July 30, 2003, at 06:40 PM, Alexandre Duret-Lutz wrote:

> Here is a second version of this section, so that we have

This looks great -- it's very clear indeed.  As an ignorant user, I'm 
much more confident that I know what's going on.  I have a few comments.

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> Libtool abstracts shared and static libraries into a unified concept
> henceforth called "libtool libraries".  Libtool libraries are files
> using the `.la' suffix, and can designate a static library, a shared
> [...]
> the `.lo' suffix.  Libtool libraries are built from these libtool
> objects.

[I would add, here:]

You don't need to know anything about the structure of `.la' or `.lo' 
files (and they are subject to change), but it is these files that 
libtool and automake use to coordinate the dependencies in a package, 
and it is these which you should use to express those dependencies.  In 
other words, the existence of the libtool libraries and objects is part 
of the automake API; the content is not.

[Incidentally, pace Guido, I agree with Alexandre that giving any 
detail about the .libs directory is probably undesirable, other than 
perhaps saying `no user-servicable parts inside'.  The typical users of 
automake are likely to be the sort of folk who aren't shy of looking at 
the source  to work out what's possible; thus this manual is possibly 
unusual in being heavily concerned with what users should _not_ hack 
at, if they want their makefiles to survive the next automake upgrade.  
Less of a manual, more a style-guide, perhaps?]

[...]

Also, note that if you include the declarations for building a shared 
library, automake will automatically build the corresponding static 
library [this is true, isn't it?]  Thus you do _not_ need to include 
and configure (and keep in sync!) both sets of rules.

>    The important implementation detail you have to bwe aware of is that

[typo: `be aware']

>    For libraries whose destination directory is known when Automake
> runs, Automake will automatically supply the appropriate `-rpath'
> option to libtool. This is the case for libraries listed explicitly in
> some `DIR_LTLIBRARIES' variable.

[I'm not sure exactly what this means (I'm valuably ignorant about 
automake, remember!).  How about:]

...in some `_LTLIBRARIES' variable, such as `lib_LTLIBRARIES'.

[...if that's correct]

> Libtool Libraries with Conditional Sources
> ------------------------------------------
>
> Conditional compilation of sources in a library can be achieved in the
> same way as conditional compilation of sources in a program (*note
> Conditional Sources::).  The only difference is that `_LIBADD' should
> be used instead of `_LDADD' and that it should mention libtool objects
> (`.lo' files).

[This was the thing that was terribly unclear to me before]

>    Nowadays, the computation of `LTLIBOBJS' for `LIBOBJS' is performed
> automatically by Autoconf (*note `AC_LIBOBJ' vs. `LIBOBJS':
> (autoconf)AC_LIBOBJ vs LIBOBJS.).

[?add]

Recall that you will typically not assign to either `LIBOBJS' or 
`LTLIBOBJS', either in `automake' or `configure'; your only contact 
with it is to declare which library depends on these missing functions. 
[or am I still confused, sigh?]




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I hope these are useful.

All the best,

Norman


--
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Norman Gray                   http://www.astro.gla.ac.uk/users/norman/
Physics and Astronomy, University of Glasgow    address@hidden