libtool--gary--1.0--patch-43

[Gary V. Vaughan]

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Hash: SHA1

I decided that my proposal for dlpreopening a non-module dependency
library (i.e libdlloader.la) along with contingent and unused symbol
import glue was just an ugly hack.

I like this solution much better.  It comes with a bunch of all new
documentation that explains what it is for (and a bunch of all new
code that documents how it is done ;-)).

Okay to apply?

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
_________________________________________________________
This patch notification generated by tlaapply version 0.5
http://tkd.kicks-ass.net/arch/address@hidden/cvs-utils--tla--1.0
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* looking for address@hidden/libtool--gary--1.0--patch-42 to compare with
* comparing to address@hidden/libtool--gary--1.0--patch-42
M  ChangeLog
M  NEWS
M  doc/libtool.texi
M  libltdl/Makefile.am
M  config/ltmain.in

* modified files

Index: Changelog
from  Gary V. Vaughan  <address@hidden>
        Add a new `-weak' flag to tell libtool when not to propogate
        dependency libraries from dlpreopened modules to libraries:

        * config/ltmain.in: Support new -weak link mode option.  Adjust
        help message.
        * libltdl/Makefile.am (libltdlc_la_LDFLAGS): Use it.
        * doc/libtool.texi (Linking with dlopened modules): Document it.
        (Link mode): Mention -weak.
        * NEWS: Updated.

2004-08-27  Gary V. Vaughan  <address@hidden>

--- orig/NEWS
+++ mod/NEWS
@@ -31,6 +31,8 @@
 * If you configure libtool with --disable-shared (or if libtool does not
   support shared libraries on your platform) trying to build a library using
   `-shared' is a fatal error.
+* New link mode option `-weak' tells libtool when not to propogate dependency
+  libraries from dlpreopened modules.
 * libtoolize installs libtool.m4, (ltdl.m4 if used,) and various supporting
   m4 definitions to AC_CONFIG_MACRO_DIR.
 * Mode inferrence removed, shorthand for choosing modes added.


--- orig/config/ltmain.in
+++ mod/config/ltmain.in
@@ -1309,6 +1309,7 @@
     thread_safe=no
     vinfo=
     vinfo_number=no
+    weak_libs=
 
     func_infer_tag $base_compile
 
@@ -1428,18 +1429,21 @@
          prev=
          continue
          ;;
-       inst_prefix)
-         inst_prefix_dir="$arg"
-         prev=
-         continue
-         ;;
-       precious_regex)
-         precious_files_regex="$arg"
+       framework)
+         case $host in
+           *-*-darwin*)
+             case "$deplibs " in
+               *" $qarg.ltframework "*) ;;
+               *) deplibs="$deplibs $qarg.ltframework" # this is fixed later
+                  ;;
+             esac
+             ;;
+         esac
          prev=
          continue
          ;;
-       release)
-         release="-$arg"
+       inst_prefix)
+         inst_prefix_dir="$arg"
          prev=
          continue
          ;;
@@ -1550,6 +1554,16 @@
          prev=
          continue
          ;;
+       precious_regex)
+         precious_files_regex="$arg"
+         prev=
+         continue
+         ;;
+       release)
+         release="-$arg"
+         prev=
+         continue
+         ;;
        rpath | xrpath)
          # We need an absolute path.
          case $arg in
@@ -1573,19 +1587,14 @@
          prev=
          continue
          ;;
-       xcompiler)
-         compiler_flags="$compiler_flags $qarg"
+       shrext)
+         shrext_cmds="$arg"
          prev=
-         compile_command="$compile_command $qarg"
-         finalize_command="$finalize_command $qarg"
          continue
          ;;
-       xlinker)
-         linker_flags="$linker_flags $qarg"
-         compiler_flags="$compiler_flags $wl$qarg"
+       weak)
+         weak_libs="$weak_libs $arg"
          prev=
-         compile_command="$compile_command $wl$qarg"
-         finalize_command="$finalize_command $wl$qarg"
          continue
          ;;
        xcclinker)
@@ -1596,22 +1605,19 @@
          finalize_command="$finalize_command $qarg"
          continue
          ;;
-       framework)
-         case $host in
-           *-*-darwin*)
-             case "$deplibs " in
-               *" $qarg.ltframework "*) ;;
-               *) deplibs="$deplibs $qarg.ltframework" # this is fixed later
-                  ;;
-             esac
-             ;;
-         esac
+       xcompiler)
+         compiler_flags="$compiler_flags $qarg"
          prev=
+         compile_command="$compile_command $qarg"
+         finalize_command="$finalize_command $qarg"
          continue
          ;;
-       shrext)
-         shrext_cmds="$arg"
+       xlinker)
+         linker_flags="$linker_flags $qarg"
+         compiler_flags="$compiler_flags $wl$qarg"
          prev=
+         compile_command="$compile_command $wl$qarg"
+         finalize_command="$finalize_command $wl$qarg"
          continue
          ;;
        *)
@@ -1669,6 +1675,11 @@
        continue
        ;;
 
+      -framework)
+       prev=framework
+       continue
+       ;;
+
       -inst-prefix-dir)
        prev=inst_prefix
        continue
@@ -1783,11 +1794,6 @@
        continue
        ;;
 
-      -shrext)
-       prev=shrext
-       continue
-       ;;
-
       -no-fast-install)
        fast_install=no
        continue
@@ -1861,6 +1867,11 @@
        continue
        ;;
 
+      -shrext)
+       prev=shrext
+       continue
+       ;;
+
       -static)
        # The effects of -static are defined in a previous loop.
        # We used to do the same as -all-static on platforms that
@@ -1879,12 +1890,18 @@
        prev=vinfo
        continue
        ;;
+
       -version-number)
        prev=vinfo
        vinfo_number=yes
        continue
        ;;
 
+      -weak)
+        prev=weak
+       continue
+       ;;
+
       -Wc,*)
        args=`$echo "X$arg" | $Xsed -e "$sed_quote_subst" -e 's/^-Wc,//'`
        arg=
@@ -1937,11 +1954,6 @@
        continue
        ;;
 
-      -framework)
-       prev=framework
-       continue
-       ;;
-
       # Some other compiler flag.
       -* | +*)
        # Unknown arguments in both finalize_command and compile_command need
@@ -2241,16 +2253,21 @@
        # Collect and forward deplibs of preopened libtool libs
        for lib in $dlprefiles; do
          # Ignore non-libtool-libs
+         dependency_libs=
          case $lib in
-         */*.la | *\\*.la)
-           . $lib
-           deplibs="$deplibs $dependency_libs"
-           ;;
-         *.la)
-           . ./$lib
-           deplibs="$deplibs $dependency_libs"
-           ;;
+         *[\\/]*.la) . $lib   ;;
+         *.la)       . ./$lib ;;
          esac
+
+         # Collect preopened libtool deplibs, except any this library
+         # has declared as weak libs
+         for deplib in $dependency_libs; do
+            deplib_base=`echo "$deplib" |$SED "$basename"`
+           case " $weak_libs " in
+           *" $deplib_base "*) ;;
+           *) deplibs="$deplibs $deplib" ;;
+           esac
+         done
        done
        libs="$dlprefiles"
       fi
@@ -5589,6 +5606,9 @@
 # Libraries that this one depends upon.
 dependency_libs='$dependency_libs'
 
+# Names of additional weak libraries provided by this library
+weak_library_names='$weak_libs'
+
 # Version information for $libname.
 current=$current
 age=$age
@@ -6704,6 +6724,7 @@
   -static           do not do any dynamic linking of libtool libraries
   -version-info CURRENT[:REVISION[:AGE]]
                    specify library version info [each variable defaults to 0]
+  -weak LIBNAME     declare that the target provides the LIBNAME interface
 
 All other options (arguments beginning with \`-') are ignored.
 


--- orig/doc/libtool.texi
+++ mod/doc/libtool.texi
@@ -166,6 +166,7 @@
 
 * Building modules::            Creating dlopenable objects and libraries.
 * Dlpreopening::                Dlopening that works on static platforms.
+* Linking with dlopened modules:: Using dlopenable modules in libraries.
 * Finding the dlname::          Choosing the right file to @code{dlopen}.
 * Dlopen issues::               Unresolved problems that need your attention.
 
@@ -1427,6 +1428,13 @@
 operating systems.  New projects should use the @samp{-version-info} flag
 instead.
 
address@hidden -weak @var{libname}
+if @var{output-file} is a libtool library, declare that it provides a
+weak @var{libname} interface.  This is a hint to libtool that there is
+no need to append @var{libname} to the list of dependency libraries of
address@hidden, because linking against @var{output-file} already
+supplies the same interface (@pxref{Linking with dlopened modules}).
+
 @item -Wl,@var{flag}
 @itemx -Xlinker @var{flag}
 Pass a linker specific flag directly to the linker.
@@ -2884,6 +2892,7 @@
 @menu
 * Building modules::            Creating dlopenable objects and libraries.
 * Dlpreopening::                Dlopening that works on static platforms.
+* Linking with dlopened modules:: Using dlopenable modules in libraries.
 * Finding the dlname::          Choosing the right file to @code{dlopen}.
 * Dlopen issues::               Unresolved problems that need your attention.
 @end menu
@@ -3071,6 +3080,112 @@
 @end deftypefun
 
 
address@hidden Linking with dlopened modules
address@hidden Linking with dlopened modules
address@hidden linking, dlopen
address@hidden linking, dlpreopen
+
+When, say, an interpreter application uses dlopened modules to extend
+the list of methods it provides, an obvious abstraction for the
+maintainers of the interpreter is to have all methods (including the
+built in ones supplied with the interpreter) accessed through
+dlopen.  For one thing, the dlopening functionality will be tested
+even during routine invocations.  For another, only one subsystem has
+to be written for getting methods into the interpreter.
+
+The downside of this abstraction is, of course, that environments that
+provide only static linkage can't even load the intrinsic interpreter
+methods.  Not so!  We can statically link those methods by
address@hidden them.
+
+Unfortunately, since platforms such as @sc{aix} and cygwin require
+that all library symbols must be resolved at compile time, the
+interpreter maintainers will need to provide a library to both its own
+dlpreopened modules, and third-party modules loaded by dlopen.  In
+itself, that is not so bad, except that the interpreter too must
+provide those same symbols otherwise it will be impossible to resolve
+all the symbols required by the modules as they are loaded.  Things
+are even worse if the code that loads the modules for the interpreter
+is itself in a library -- and that is usually the case for any
+non-trivial application.  Modern platforms take care of this by
+automatically loading all of a module's dependency libraries as the
+module is loaded (libltdl can do this even on platforms that can't do
+it by themselves).  In the end, this leads to problems with duplicated
+symbols and prevents modules from loading, and prevents the
+application from compiling when modules are preloaded.
+
address@hidden
+,-------------.    ,------------------.    ,-----------------.
+| Interpreter |---->     Module------------>   Third-party   |
+`-------------'    |     Loader       |    |Dlopened Modules |
+                   |        |         |    `-----------------'
+                   |,-------v--------.|             |
+                   ||  Dlpreopened   ||             |
+                   ||    Modules     ||             |
+                   |`----------------'|             |
+                   |        |         |             |
+                   |,-------v--------.|    ,--------v--------.
+                   ||Module Interface||    |Module Interface |
+                   ||    Library     ||    |     Library     |
+                   |`----------------'|    `-----------------'
+                   `------------------'
address@hidden example
+
+Libtool has the concept of @dfn{weak library interfaces} to circumvent
+this problem.  Recall that the code that dlopens method-provider
+modules for the interpreter application resides in a library: All of
+the modules and the dlopener library itself should be linked against
+the common library that resolves the module symbols at compile time.
+To guard against duplicate symbol definitions, and for dlpreopened
+modules to work at all in this scenario, the dlopener library must
+declare that it provides a weak library interface to the common
+symbols in the library it shares with the modules.  That way, when
address@hidden links the @strong{Module Loader} library with some
address@hidden Modules} that were in turn linked against the
address@hidden Interface Library}, it knows that the @strong{Module
+Loader} provides an already loaded @strong{Module Interface Library}
+to resolve symbols for the @strong{Dlpreopened Modules}, and doesn't
+ask the compiler driver to link an identical @strong{Module Interface
+Library} dependency library too.
+
+In conjunction with Automake, the @file{Makefile.am} for the
address@hidden Loader} might look like this:
+
address@hidden
+lib_LTLIBRARIES = libinterface.la libloader.la
+
+libinterface_la_SOURCES = interface.c interface.h
+libinterface_la_LDFLAGS = -version-info 3:2:1
+
+libloader_la_SOURCES    = loader.c
+libloader_la_LDFLAGS    = -weak libinterface.la \
+                          -version-info 3:2:1 \
+                          -dlpreopen ../modules/intrinsics.la
+libloader_la_LIBADD     = $(libinterface_la_OBJECTS)
address@hidden example
+
+And the @file{Makefile.am} for the @file{intrinsics.la} module in a
+sibling @file{modules} directory might look like this:
+
address@hidden
+AM_CPPFLAGS             = -I$(srcdir)/../libloader
+AM_LDFLAGS              = -no-undefined -module -avoid-version \
+                          -export-dynamic
+
+noinst_LTLIBRARIES      = intrinsics.la
+
+intrinsics_la_LIBADD    = ../libloader/libinterface.la
+
+../libloader/libinterface.la:
+        cd ../libloader; $(MAKE) $(AM_MAKEFLAGS) libinterface.la
address@hidden example
+
address@hidden -weak option
+For a more complex example, see the sources of @file{libltdl} in the
+Libtool distribution, which is built with the help of the @samp{-weak}
+option.
+
+
 @node Finding the dlname
 @section Finding the correct name to dlopen
 @cindex names of dynamic modules


--- orig/libltdl/Makefile.am
+++ mod/libltdl/Makefile.am
@@ -62,7 +62,7 @@
 
 libltdlc_la_SOURCES    = $(libltdl_la_SOURCES)
 libltdlc_la_CPPFLAGS   = -DLTDLOPEN=libltdlc $(AM_CPPFLAGS)
-libltdlc_la_LDFLAGS    = $(LT_DLPREOPEN)
+libltdlc_la_LDFLAGS    = -weak libdlloader.la $(LT_DLPREOPEN)
 libltdlc_la_LIBADD     =  $(libdlloader_la_OBJECTS) $(libdlloader_la_LIBADD)
 
 ## These are installed as a subdirectory of pkgdatadir so that