[Pythonmac-SIG] [PATCH]: Python should use dlopen() on 10.3+
Ronald Oussoren
ronaldoussoren at mac.com
Mon Mar 20 10:05:43 CET 2006
On 20-mrt-2006, at 4:13, Zachary Pincus wrote:
> Hello folks,
>
> Here is a patch to make Python on OS X 10.3 and above use dlopen()
> (via dynload_shlib.c) to load extension modules, and to make the dl
> module avaliable. It ought to be incorporated into the SVN for python
> 2.5, if not for further development on 2.4.
>
> If this is an inappropriate channel for this patch, please let me
> know to where I should direct it. Bob Ippolito initially suggested
> this patch be sent hither.
Please file this patch on sourceforge.net (www.sf.net/projects/python)
Ronald
>
> Zach Pincus
> Program in Biomedical Informatics and Department of Biochemistry
> Stanford University School of Medicine
>
>
> RATIONALE
> ---------
> On most other unix-like operating systems, Python uses the dlopen()
> call to load extension modules. In addition, the way that these
> modules are opened can be modified via 'sys.setdlopenflags(...)'.
>
> Modifications of how extensions are loaded are useful for several
> reasons (enough so that the standard Python docs (e.g. http://
> docs.python.org/lib/module-sys.html ). In particular, if multiple
> modules need to share symbols, a call to sys.setdlopenflags is
> necessary.
>
> Symbol sharing is especially important for interoperability of
> modules which wrap C++ classes, because GCC creates classes that
> resolve their run-time type identification by symbol identity. Thus,
> symbols must be shared globally for many C++ features to work
> properly for objects passed between modules.
>
> On OS X / Darwin, Python uses some NeXT-derived APIs to load modules.
> Though these APIs provide analogues to the dlopenflags used to
> control how dlopen() loads modules, this interface is *not* exposed
> to the Python interpreter. Worse, sys.setdlopenflags remains
> available on Darwin, though calls to it are never heeded.
>
> Fortunately, on OS X 10.3 and above, Apple has included dlopen as a
> standard function. In 10.3, this call is provided by a compatibility
> API; in 10.4, the dlopen() call is written to interface directly with
> the library loading mechanism and is now the recommended method for
> libraries to be opened for non Carbon/Cocoa tools.
>
> IMPLEMENTATION
> --------------
> This (trivial) patch instructs the Python build process to use
> dynload_shlib.c (which uses dlopen) instead of dynload_next.c (which
> uses the NeXT-derived APIs). It also allows for the dl module to be
> built in order to provide access to the proper values for the various
> dlopen flags.
>
> TESTING
> -------
> This patch can be configured and built into executables that build
> and test correctly on 10.3 and 10.4. The patch is nominally targeted
> at the SVN head as of today, but can be applied (and I have done so
> with success) to Python 2.4.2.
>
> Because Python 2.5 and 2.4 do not currently compile properly on OS X
> 10.2, I have not built or tested this patch on that OS version.
> However, the configure and compile process does select the
> appropriate dynload_next.c file to use, and compiles that correctly
> before breaking elsewhere. Thus, if the other errors are fixed for
> 10.2, these patches will work fine. (This is because they only change
> Python's behavior for 10.3 and up.)
>
> PATCHES
> -------
> Here are three sets of patches, as unified diffs.
>
> FIRST: Patch the configure.in file to use dynload_shlib.c when it
> can. Also regenerate the configure script.
>
> Index: configure.in
> ===================================================================
> --- configure.in (revision 43150)
> +++ configure.in (working copy)
> @@ -2105,7 +2105,8 @@
> ;;
> BeOS*) DYNLOADFILE="dynload_beos.o";;
> hp*|HP*) DYNLOADFILE="dynload_hpux.o";;
> - Darwin/*) DYNLOADFILE="dynload_next.o";;
> + # Use dynload_next.c only on 10.2 and below, which don't have
> native dlopen()
> + Darwin/@<:@0123456@:>@.*) DYNLOADFILE="dynload_next.o";;
> atheos*) DYNLOADFILE="dynload_atheos.o";;
> *)
> # use dynload_shlib.c and dlopen() if we have it; otherwise
> stub
> Index: configure
> ===================================================================
> --- configure (revision 43150)
> +++ configure (working copy)
> @@ -1,5 +1,5 @@
> #! /bin/sh
> -# From configure.in Revision: 42437 .
> +# From configure.in Revision: 42563 .
> # Guess values for system-dependent variables and create Makefiles.
> # Generated by GNU Autoconf 2.59 for python 2.5.
> #
> @@ -13974,7 +13974,8 @@
> ;;
> BeOS*) DYNLOADFILE="dynload_beos.o";;
> hp*|HP*) DYNLOADFILE="dynload_hpux.o";;
> - Darwin/*) DYNLOADFILE="dynload_next.o";;
> + # Use dynload_next.c only on 10.2 and below, which don't have
> native dlopen()
> + Darwin/[0123456].*) DYNLOADFILE="dynload_next.o";;
> atheos*) DYNLOADFILE="dynload_atheos.o";;
> *)
> # use dynload_shlib.c and dlopen() if we have it; otherwise
> stub
>
>
>
> SECOND: Allow the dl module to be built and tested
>
>
> Index: setup.py
> ===================================================================
> --- setup.py (revision 43150)
> +++ setup.py (working copy)
> @@ -883,7 +883,7 @@
> if sys.maxint == 0x7fffffff:
> # This requires sizeof(int) == sizeof(long) == sizeof
> (char*)
> dl_inc = find_file('dlfcn.h', [], inc_dirs)
> - if (dl_inc is not None) and (platform not in ['atheos',
> 'darwin']):
> + if (dl_inc is not None) and (platform not in ['atheos']):
> exts.append( Extension('dl', ['dlmodule.c']) )
> # Thomas Heller's _ctypes module
> Index: Lib/test/test_dl.py
> ===================================================================
> --- Lib/test/test_dl.py (revision 43150)
> +++ Lib/test/test_dl.py (working copy)
> @@ -10,6 +10,7 @@
> ('/usr/lib/libc.so', 'getpid'),
> ('/lib/libc.so.6', 'getpid'),
> ('/usr/bin/cygwin1.dll', 'getpid'),
> + ('/usr/lib/libc.dylib', 'getpid'),
> ]
> for s, func in sharedlibs:
>
>
>
> THIRD: (optional) Tell Python that the dl test is not expected to be
> skipped anymore. This is optional because if Python is ever built on
> 10.2, the test script will expect dl to work, when it only works on
> 10.3 and above. However, if Python on 10.2 is officially not
> supported, then this change should be made to properly test the dl
> functionality.
>
>
> Index: Lib/test/regrtest.py
> ===================================================================
> --- Lib/test/regrtest.py (revision 43150)
> +++ Lib/test/regrtest.py (working copy)
> @@ -930,7 +930,6 @@
> test_cd
> test_cl
> test_curses
> - test_dl
> test_gdbm
> test_gl
> test_imgfile
>
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