On 17 September 2010 11:34, Gustavo Sverzut Barbieri
<[email protected]> wrote:
> On Fri, Sep 17, 2010 at 11:07 AM, Lisandro Dalcin <[email protected]> wrote:
>> On 17 September 2010 10:07, Gustavo Sverzut Barbieri
>> <[email protected]> wrote:
>>> changeset: 3753:62e52f105bc0
>>> tag: tip
>>> user: Gustavo Sverzut Barbieri <[email protected]>
>>> date: Fri Sep 17 09:42:57 2010 -0300
>>> files: Cython/Compiler/ModuleNode.py
>>> description:
>>> Force GCC>=4 to export module initialization function.
>>>
>>> With GCC's -fvisibility=hidden (both CFLAGS and LDFLAGS) it is
>>> possible to have the compiler to produce binaries where all symbols
>>> are hidden (local to the binary). To force a symbol to be visible one
>>> must specify __attribute__ ((visibility("default"))).
>>>
>>
>> Why do you need to force -fvisibility=hidden ? In general, Cython
>> emits 'static' storage specifier, unless 'public' or 'api' keywords
>> are involved.
>
> I don't. But we recently moved from setuptools to autoconf due lots of
> complaints of the former and I got tired and wasted 2 days to convert
> all my bindings, and users had that in their CFLAGS as the whole
> project compiles with it... except our bindings :-/
>
> As for autoconf, later on I'll post the link to our examples... I even
> created a cython.m4 to help finding cython, its version and already
> cythonized files. What made us run away from setuptools is the deep
> level of magic and dynamic patching: setuptools/distutils checked for
> pyrex, thus I was faking cython as pyrex in sys.__modules__, but then
> people asked for easy_install and that was importing setuptools before
> we fake pyrex and then to unpatch all the classes was being a major
> PITA. autoconf/automake is not much easier, as it requires lots of
> code to get something done, but at least the rest of our developers
> are used to it due the C libraries... :-/
>
>
>>> This patch introduces pre-processor code to always force module
>>> symbols to be visible.
>>>
>>> NOTE: in theory pyport.h from Python would do the right thing, but it
>>> does not define any special cases for GCC, just Windows. As Python is
>>> not changing that easily and even if it does is just for future releases,
>>> it's better to have those in Cython.
>>>
>>
>> Did you bug Python?
>
> not yet...
>
>
>>> diff --git a/Cython/Compiler/ModuleNode.py b/Cython/Compiler/ModuleNode.py
>>> --- a/Cython/Compiler/ModuleNode.py
>>> +++ b/Cython/Compiler/ModuleNode.py
>>> @@ -1671,9 +1671,15 @@
>>> header2 = "PyMODINIT_FUNC init%s(void)" % env.module_name
>>> header3 = "PyMODINIT_FUNC PyInit_%s(void)" % env.module_name
>>> code.putln("#if PY_MAJOR_VERSION < 3")
>>> + code.putln("# if defined(__GNUC__) && (__GNUC__ >= 4)")
>>> + code.putln("__attribute__ ((visibility(\"default\")))")
>>> + code.putln("# endif")
>>> code.putln("%s; /*proto*/" % header2)
>>> code.putln(header2)
>>> code.putln("#else")
>>> + code.putln("# if defined(__GNUC__) && (__GNUC__ >= 4)")
>>> + code.putln("__attribute__ ((visibility(\"default\")))")
>>> + code.putln("# endif")
>>> code.putln("%s; /*proto*/" % header3)
>>> code.putln(header3)
>>> code.putln("#endif")
>>>
>>
>> It looks good, I support the patch. However,
>>
>> 1) Do you know how this would work in Windows with MinGW? I would
>> MinGW to do the right thing, but we have to be sure...
>
> AFAIK it does the right thing as we have libraries with that and it
> still work. Right now I don't have people to check it, but if you wish
> we could add a !windows before the check for gcc.
>
No, I would prefer to test your patch in Windows and see if things
still work. But that would be next week.
>
>> 2) Do you know if this could affect full static Python builds? (I
>> mean, when you build a Python interpreter with all ext modules
>> 'built-in' in the python binary) ? I cannot think of any problem, but
>> perhaps you do?
>
> no problems other than the symbol will be visible.
>
Well, that could be a problem... Perhaps we should define a
CYTHON_MODINIT_FUNC_VISIBILITY macro, then as a last resort you can
change it. I'm thinking on something like:
#if !defined(CYTHON_MODINIT_FUNC_VISIBILITY)
#if defined(__GNUC__) && (__GNUC__ >= 4)
#define CYTHON_MODINIT_FUNC_VISIBILITY __attribute__ ((visibility("default")))
#else
#define CYTHON_MODINIT_FUNC_VISIBILITY
#endif
#endif
and then we can emit code like this:
PyMODINIT_FUNC init<name>(void)
CYTHON_MODINIT_FUNC_VISIBILITY
{
....
}
What do you think?
--
Lisandro Dalcin
---------------
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