RFC on Makefile.am fixes for (non-portable) linking against libtool modules in KDE

Benjamin Reed ranger at befunk.com
Thu Mar 6 03:25:10 GMT 2003

I had brought this up previously pre-kde-3.1 while working on the MacOSX 
port of KDE, but as Sam Magnuson and I are working to get our patches 
all figured out, I figured I'd better bring it up again.

The short version is, libtool libraries built as -module's are not meant 
to be linked against, but through the magic of the ELF library format 
and libtool not enforcing this policy, it works 95% of the time anyways. 
  The big problem with this on MacOSX/Darwin is that Darwin's dynamic 
loader does *not* allow loading libtool modules (or "bundles", in Darwin 

If it was just a few libraries, it would be easy to work around, but 
KDE's kdeinit library/binary magic does this, and it's all over the 
place in the KDE code.

The current "fix" looks something like this:


lib_LTLIBRARIES = foo.la
bin_PROGRAMS    = foo

foo_la_SOURCES = foo.cpp
foo_la_LDFLAGS = $(all_libraries) -module

foo_SOURCES = dummy.cpp
foo_LDADD   = foo.la


lib_LTLIBRARIES = libfoo_main.la foo.la
bin_PROGRAMS    = foo

libfoo_main_la_SOURCES = foo.cpp
libfoo_main_la_LDFLAGS = $(all_libraries)

foo_la_SOURCES = stub_la.cpp
foo_la_LIBADD  = libfoo_main.la

foo_SOURCES = stub.cpp
foo_LDADD   = libfoo_main.la

stub_la.cpp: stub.cpp
	cat stub.cpp > stub_la.cpp


extern "C" int kdemain(int, char* []);

int main( int argc, char* argv[] )
         return kdemain(argc, argv);


...and then the "int main" gets turned into "int kdemain" inside 
whatever defines main.  (foo.cpp in this case)

As you can see, this way of munging it is perfectly doable, but rather 
brittle -- people who aren't on platforms like darwin (or, apparently, 
a.out netbsd) will forget and end up breaking things without knowing.

What I propose is some kind of automake/am_edit trickery to allow this:

---(new Makefile.am)---

# or kdebin_PROGRAMS maybe?
kdeinit_PROGRAMS = foo

# foo.cpp contains an int kdemain()
foo_SOURCES = foo.cpp
foo_LDADD = <anything but libfoo_main.la>


... it would automatically generate the module and shared library 
versions of the foo code behind the scenes, with an auto-generated stub.cpp.

Does this seem feasible?  I don't understand automake or am_edit enough 
to  do this as is, but if someone's willing to dink with it on IRC for a 
bit to make this auto-generatable, or point me at the right resources to 
make my own automake macros (which appears to be quite a black art, I've 
tried), I'm willing to do all the grunt work of fixing the things that 
need rearranging in the Makefile.am's in the KDE tree.

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