[Wheel-builders] [Matplotlib-devel] Manylinux external library test case - matplotlib, tk

[Matthew Brett]

Hi,

On Wed, May 11, 2016 at 2:26 PM, Leonardo Rochael Almeida
<leorochael at gmail.com> wrote:
> On 11 May 2016 at 10:58, Matthew Brett <matthew.brett at gmail.com> wrote:
>>
>> On Tue, May 10, 2016 at 6:38 PM, Nathaniel Smith <njs at pobox.com> wrote:
>> > On Tue, May 10, 2016 at 3:09 PM, Leonardo Rochael Almeida
>> > <leorochael at gmail.com> wrote:
>> >> On 10 May 2016 at 18:52, Matthew Brett <matthew.brett at gmail.com> wrote:
>> >>>
>> >>> On Tue, May 10, 2016 at 5:26 PM, Matthew Brett
>> >>> <matthew.brett at gmail.com>
>> >>> wrote:
>> >>> >> [...]
>> >>> >>
>> >>> >> This would probably look like:
>> >>> >>
>> >>> >> _tkagg.so has a DT_NEEDED entry naming tkinter.so (or whatever
>> >>> >> Python
>> >>> >> calls
>> >>> >> this module)
>> >>> >>
>> >>> >> Before loading _tkagg.so, we use Python level introspection figure
>> >>> >> out
>> >>> >> where
>> >>> >> tkinter.so lives
>> >>> >>
>> >>> >> We add its directory to LD_LIBRARY_PATH
>> >>> >>
>> >>> >> we import _tkagg.so
>> >>> >>
>> >>> >> We take its directory back off of LD_LIBRARY_PATH
>> >>> >>
>> >>> >> Very weird, but I can't see why it wouldn't work, and probably more
>> >>> >> reliable
>> >>> >> than anything where we try to reimplement the dynamic loader's
>> >>> >> search
>> >>> >> logic
>> >>> >> ourselves.
>> >>> >
>> >>> > Nice - yes - it does work in a first-pass test - I'll look into
>> >>> > automating that.
>> >>>
>> >>> Ah - except I do not believe it is possible to change the linker path
>> >>> for Python modules, within the Python process:
>> >>>
>> >>> http://www.gossamer-threads.com/lists/python/python/393770#393770
>> >
>> > Doh :-(
>>
>> Any other suggestions?
>
>
> Calling `patchelf` at runtime with the result of introspecting the
> `_tkinter.so` module? :-)
>
> On a more serious note, even though it would be dangerous to call
> `sys.setdlopenflags()` with `RTLD_GLOBAL`, we could perhaps manually call:
>
> ctypes.CDLL("/path/to/introspected/libtk.so", DLFCN.RTLD_GLOBAL)
> ctypes.CDLL("/path/to/introspected/libtcl.so", DLFCN.RTLD_GLOBAL)
>
> before importing a `_tkagg.so` with `libtk` and `libtcl` patchelf-removed
> (but not re-added).
>
> We would be dumping only libtcl/tk's symbols in the namespace of other
> python extension modules.

I have implemented dlopen dynamic loading of the TCL / Tk functions
from the Python tkinter extension module here :
https://github.com/matplotlib/matplotlib/pull/6442

It appears to work.   I'd love any feedback y'all can offer.

Cheers,

Matthew