[LLVMdev] Problems loading passes on Mac OS X

Chris Lattner sabre at nondot.org
Sun Jun 20 04:12:01 PDT 2004 

On Sun, 20 Jun 2004, Michael McCracken wrote:

> Solved.

Yaay!

> Short version:
>
> You don't need to change DynamicLinker.cpp at all. dlopen() should just
> work, except that the defaults for libtool are to produce the wrong
> kind of shared object.

Okay.

> On OS X, libtool needs to be passed the -module option to create
> dlopen-able objects:
>
> % diff Makefile.rules.old Makefile.rules
> 326c326
> < Link     := $(LIBTOOL) --mode=link $(CXX)
> ---
>  > Link     := $(LIBTOOL) --mode=link $(CXX) -module
>
> This hack isn't a complete fix, because SHLIBEXT is still set wrong.
> (It should be .so not .dylib). I couldn't figure out how to do that
> right, so I didn't try and it didn't matter for getting it running,
> although it's clear some make targets are messed up.

Okay, I'm glad that this is working for you and that you found the root
cause of the problem.  I will defer to one of our autoconf/libtool experts
on how to get this implemented correctly and portably.  In particular, it
seems like the incorrect detection of SHLIBEXT could be a blocker until it
is fixed.

-Chris


> Elaboration:
>
> not passing -module makes libtool use 'g++ -dynamiclib', which creates
> Mach-O MH_DYLIB files, that only have static ctors called if a symbol
> in that same file is used. (I got it to work by dlsym'ing the mangled
> ctor's name, but that's not a solution.)
>
> if you pass -module, libtool uses 'g++ -bundle', which creates Mach-O
> MH_BYNDLE files, that work as dlopen() expects.
>
> Apparently the reason there are these two types of Mach-O files is that
> you can use a .dylib with a static linker as well as being loaded. I
> guess this isn't a big deal when using libtool anyway.
>
> (End Elaboration)
>
> So, I'm set to work, and hopefully this gives you enough info to add on
> OS X plugin loading support. I'm a little too tired now to try to
> figure out exactly how to set up configure.ac and Makefile.rules, but
> I'm hoping someone else will know already and it'll be easy.
>
> Let me know if I can be of any more help for this, and thanks for your
> help!
> -mike
>
> On Jun 19, 2004, at 5:11 PM, Michael McCracken wrote:
>
> > OK, seems like I've got some more looking to do.
> > From what I can find, the only difference with OS X and dynamic
> > libraries is that you can't depend on the order of calling static
> > constructors, but not that you can't depend on them getting called. :)
> >
> > If I find that library handling in LLVM needs changes to work with OS
> > X, I'll send a patch.
> >
> > Thanks,
> > -mike
> >
> > On Jun 19, 2004, at 3:25 PM, Chris Lattner wrote:
> >
> >> On Sat, 19 Jun 2004, Michael McCracken wrote:
> >>> I used the following short code to test loading the .dylib, and
> >>> dlopen
> >>> works fine, but dlsym is less pretty - on OS X, it automatically
> >>> prepends an underscore to the symbol, which means that if you are
> >>> looking for main(), you ask for "main" and it looks for "_main",
> >>> which
> >>> is how the symbols are named in Mach-O.
> >>> This could be the source of a problem - how does GetAddressOfSymbol
> >>> in
> >>> DynamicLinker.cpp use dlsym?
> >>
> >> I believe that GetAddressOfSymbol is only used by the JIT.  The -load
> >> mechanism just dlopens a shared object.  Shared objects for plugins
> >> have
> >> static constructors (".init" section) that are supposed to
> >> autoregister
> >> the pass when the plugin is loaded.
> >>
> >> I don't know anything about how dynamic object loading works on OS/X
> >> (obviously), but it sounds like it's not running the static
> >> constructor.
> >>
> >>> Does it assume anything about the symbol names?
> >>
> >> I don't know what it will take to get the JIT working on OS/X: it
> >> might
> >> have to autoprepend an _.  Since we don't (yet) have a PPC JIT, this
> >> isn't
> >> an issue though.
> >>
> >> -Chris
> >>
> >>
> >>
> >>> On Jun 19, 2004, at 2:07 PM, Chris Lattner wrote:
> >>>
> >>>> On Sat, 19 Jun 2004, Michael McCracken wrote:
> >>>>
> >>>>> Hi, I can't get opt to list (in -help) passes that I load using
> >>>>> -load.
> >>>>> I see in the list archives that a similar problem has been brought
> >>>>> up
> >>>>> before but I didn't see whether it was resolved. Also, this is on
> >>>>> Mac
> >>>>> OS X, and the previous question was about Linux.
> >>>>
> >>>> The problem is that this has not been implemented yet on Mac OSX.
> >>>> If
> >>>> you're familiar with the OS/X interfaces for loading .so files, it
> >>>> should
> >>>> be pretty easy.  Take a look at lib/Support/DynamicLinker.cpp.  I
> >>>> think
> >>>> that OS/X doesn't have windows.h :), and it also doesn't have
> >>>> dlopen.
> >>>> If
> >>>> you can provide the necessary magic for your platform, it should
> >>>> just
> >>>> work.
> >>>>
> >>>> -Chris
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> This problem happens with the Hello pass, so I'll use that to
> >>>>> illustrate. I'm using LLVM 1.2.
> >>>>> The plugin loads with no complaints, so dlopen() is returning
> >>>>> success,
> >>>>> and OS X's dlcompat probably isn't the problem.
> >>>>> However, it never gets registered. I've included a transcript
> >>>>> below.
> >>>>>
> >>>>> I also included some info about the compiler versions, etc. - It's
> >>>>> OS
> >>>>> X
> >>>>> 10.3.4.
> >>>>> Note that on OS X, 'libtool' isn't gnu libtool - that's called
> >>>>> 'glibtool', if that matters.
> >>>>>
> >>>>> Does anyone have some hints on how to get this working? Thanks.
> >>>>>
> >>>>> transcript:
> >>>>>
> >>>>> % cd llvm/lib/Transforms/Hello/
> >>>>> % make
> >>>>> Compiling Hello.cpp
> >>>>> Linking hello dynamic debug library
> >>>>> -------------------------------------------------------------------
> >>>>> ---
> >>>>> Libraries have been installed in:
> >>>>>     /Users/mike/Documents/hpcl/LLVM/llvm/lib/Debug
> >>>>>
> >>>>> If you ever happen to want to link against installed libraries
> >>>>> in a given directory, LIBDIR, you must either use libtool, and
> >>>>> specify the full pathname of the library, or use the `-LLIBDIR'
> >>>>> flag during linking and do at least one of the following:
> >>>>>     - add LIBDIR to the `DYLD_LIBRARY_PATH' environment variable
> >>>>>       during execution
> >>>>>
> >>>>> See any operating system documentation about shared libraries for
> >>>>> more information, such as the ld(1) and ld.so(8) manual pages.
> >>>>> -------------------------------------------------------------------
> >>>>> ---
> >>>>> ======= Finished building hello dynamic debug library =======
> >>>>> Linking hello.o
> >>>>>
> >>>>> % opt -load ../../Debug/libhello.dylib -hello
> >>>>> Unknown command line argument '-hello'.  Try: 'opt --help'
> >>>>>
> >>>>> % g++ -v
> >>>>> Reading specs from /usr/libexec/gcc/darwin/ppc/3.3/specs
> >>>>> Thread model: posix
> >>>>> gcc version 3.3 20030304 (Apple Computer, Inc. build 1495)
> >>>>>
> >>>>> % glibtool --version
> >>>>> ltmain.sh (GNU libtool) 1.5 (1.1220 2003/04/05 19:32:58)
> >>>>>
> >>>>> _______________________________________________
> >>>>> LLVM Developers mailing list
> >>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >>>>> http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
> >>>>>
> >>>>
> >>>> -Chris
> >>>>
> >>>> --
> >>>> http://llvm.cs.uiuc.edu/
> >>>> http://www.nondot.org/~sabre/Projects/
> >>>>
> >>>> _______________________________________________
> >>>> LLVM Developers mailing list
> >>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >>>> http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
> >>>>
> >>>
> >>> _______________________________________________
> >>> LLVM Developers mailing list
> >>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >>> http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
> >>>
> >>
> >> -Chris
> >>
> >> --
> >> http://llvm.cs.uiuc.edu/
> >> http://www.nondot.org/~sabre/Projects/
> >>
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
> >>
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
>
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>

-Chris

-- 
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