Bug#561413: Policy possibly should not recommend *.la files
Russ Allbery
Version: 3.8.3.0
Severity: wishlist
Policy currently says:
An ever increasing number of packages are using libtool to do their
linking. The latest GNU libtools (>= 1.3a) can take advantage of the
metadata in the installed libtool archive files (*.la files). The main
advantage of libtool's .la files is that it allows libtool to store and
subsequently access metadata with respect to the libraries it builds.
libtool will search for those files, which contain a lot of useful
information about a library (such as library dependency information for
static linking). Also, they're *essential* for programs using
libltdl.
Given the various problems that we've run into with *.la files, particularly
around adding unnecessary shared library dependencies, I wonder if this
paragraph should be revised to be a bit less encouraging about retaining
*.la files. (Although I suppose that this may change if binutils-gold and
its --as-needed default becomes the default linker.)
-- System Information:
Debian Release: squeeze/sid
APT prefers testing
APT policy: (990, 'testing'), (500, 'unstable'), (1, 'experimental')
Architecture: i386 (i686)
Kernel: Linux 2.6.30-2-686-bigmem (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
debian-policy depends on no packages.
debian-policy recommends no packages.
Versions of packages debian-policy suggests:
ii doc-base 0.9.5 utilities to manage online documen
-- no debconf information
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Bill Allombert
> Package: debian-policy
> Version: 3.8.3.0
> Severity: wishlist
>
> Policy currently says:
>
> An ever increasing number of packages are using libtool to do their
> linking. The latest GNU libtools (>= 1.3a) can take advantage of the
> metadata in the installed libtool archive files (*.la files). The main
> advantage of libtool's .la files is that it allows libtool to store and
> subsequently access metadata with respect to the libraries it builds.
> libtool will search for those files, which contain a lot of useful
> information about a library (such as library dependency information for
> static linking). Also, they're *essential* for programs using
> libltdl.
>
> Given the various problems that we've run into with *.la files, particularly
> around adding unnecessary shared library dependencies, I wonder if this
> paragraph should be revised to be a bit less encouraging about retaining
> *.la files.
Agreed.
> (Although I suppose that this may change if binutils-gold and
> its --as-needed default becomes the default linker.)
binutils-gold currently only support a subset of Debian plateforms:
(amd64, armel, i386, powerpc, sparc).
Cheers,
--
Bill. <ball...@debian.org>
Imagine a large red swirl here.
Russ Allbery
> Policy currently says:
> An ever increasing number of packages are using libtool to do their
> linking. The latest GNU libtools (>= 1.3a) can take advantage of the
> metadata in the installed libtool archive files (*.la files). The main
> advantage of libtool's .la files is that it allows libtool to store and
> subsequently access metadata with respect to the libraries it builds.
> libtool will search for those files, which contain a lot of useful
> information about a library (such as library dependency information for
> static linking). Also, they're *essential* for programs using
> libltdl.
> Given the various problems that we've run into with *.la files,
> particularly around adding unnecessary shared library dependencies, I
> wonder if this paragraph should be revised to be a bit less encouraging
> about retaining *.la files.
Here's a proposed patch that I think says what we now want to say about
*.la files. Objections or seconds?
diff --git a/policy.sgml b/policy.sgml
index 9fe7158..2635fa8 100644
--- a/policy.sgml
+++ b/policy.sgml
@@ -7361,40 +7361,58 @@ strip --strip-unneeded <var>your-lib</var>
</p>
<p>
- An ever increasing number of packages are using
- <prgn>libtool</prgn> to do their linking. The latest GNU
- libtools (>= 1.3a) can take advantage of the metadata in the
- installed <prgn>libtool</prgn> archive files (<file>*.la</file>
- files). The main advantage of <prgn>libtool</prgn>'s
- <file>.la</file> files is that it allows <prgn>libtool</prgn> to
- store and subsequently access metadata with respect to the
- libraries it builds. <prgn>libtool</prgn> will search for
- those files, which contain a lot of useful information about
- a library (such as library dependency information for static
- linking). Also, they're <em>essential</em> for programs
- using <tt>libltdl</tt>.<footnote>
- Although <prgn>libtool</prgn> is fully capable of
- linking against shared libraries which don't have
- <tt>.la</tt> files, as it is a mere shell script it can
- add considerably to the build time of a
- <prgn>libtool</prgn>-using package if that shell script
- has to derive all this information from first principles
- for each library every time it is linked. With the
- advent of <prgn>libtool</prgn> version 1.4 (and to a
- lesser extent <prgn>libtool</prgn> version 1.3), the
- <file>.la</file> files also store information about
- inter-library dependencies which cannot necessarily be
- derived after the <file>.la</file> file is deleted.
+ Packages that use <prgn>libtool</prgn> to create and install
+ their shared libraries install a file containing additional
+ metadata (ending in <file>.la</file>) alongside the library.
+ For public libraries intended for use by other packages, these
+ files normally should not be included in the Debian package,
+ since the information they include is not necessary to link with
+ the shared library on Debian and can add unnecessary additional
+ dependencies to other programs or libraries.<footnote>
+ These files store, among other things, all libraries on which
+ that shared library depends. Unfortunately, if
+ the <file>.la</file> file is present and contains that
+ dependency information, using <prgn>libtool</prgn> when
+ linking against that library will cause the resulting program
+ or library to be linked against those dependencies as well,
+ even if this is unnecessary. This can create unneeded
+ dependencies on shared library packages that would otherwise
+ be hidden behind the library ABI, and can make library
+ transitions to new SONAMEs unnecessarily complicated and
+ difficult to manage.
</footnote>
+ If the <file>.la</file> file is required for that library (if,
+ for instance, it's loaded via <tt>libltdl</tt> in a way that
+ requires that meta-information), the <tt>dependency_libs</tt>
+ setting in the <file>.la</file> file should normally be set to
+ the empty string. If the shared library development package has
+ historically included the <file>.la</file>, it must be retained
+ in the development package (with <tt>dependency_libs</tt>
+ emptied) until all libraries that depend on it have removed or
+ emptied <tt>dependency_libs</tt> in their <file>.la</file>
+ files to prevent linking with those other libraries
+ using <prgn>libtool</prgn> from failing.
+ </p>
+
+ <p>
+ If the <file>.la</file> must be included, it should be included
+ in the development (<tt>-dev</tt>) package, unless the library
+ will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
+ library. If it is intended for use with <tt>libltdl</tt>,
+ the <file>.la</file> files must go in the run-time library
+ package.
</p>
<p>
- Packages that use <prgn>libtool</prgn> to create shared
- libraries should include the <file>.la</file> files in the
- <tt>-dev</tt> package, unless the package relies on
- <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
- the <tt>.la</tt> files must go in the run-time library
- package.
+ These requirements for handling of <file>.la</file> files do not
+ apply to loadable modules or libraries not installed in
+ directories searched by default by the dynamic linker. Packages
+ installing loadable modules will frequently need to install
+ the <file>.la</file> files alongside the modules so that they
+ can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
+ does not need to be modified for libraries or modules that are
+ not installed in directories searched by the dynamic linker by
+ default and not intended for use by other packages.
</p>
<p>
--
Russ Allbery (r...@debian.org) <http://www.eyrie.org/~eagle/>
Cyril Brulebois
Russ Allbery
> Here's a proposed patch that I think says what we now want to say about
> *.la files. Objections or seconds?
This has now been merged for the next release.