python how to load multiple C libraries

Laura Creighton lac at openend.se
Thu Sep 17 11:38:39 CEST 2015


In a message of Thu, 17 Sep 2015 15:41:26 +0800, "chenchao at inhand.com.cn" write
s:
>   So, I checked my ctypes source code, I found RTLD_LAZY defined in 
>dlfcn.h header file like this:
>/* The MODE argument to `dlopen' contains one of the following: */
>#define RTLD_LAZY 0x00001 /* Lazy function call binding.  */
>#define RTLD_NOW  0x00002 /* Immediate function call binding.  */
>#define RTLD_BINDING_MASK   0x3 /* Mask of binding time value.  */
>#define RTLD_NOLOAD 0x00004 /* Do not load the object.  */
>#if 0 /* uClibc doesnt support these */
>#define RTLD_DEEPBIND 0x00008 /* Use deep binding.  */
>#endif
>
>/* If the following bit is set in the MODE argument to `dlopen',
>    the symbols of the loaded object and its dependencies are made
>    visible as if the object were linked directly into the program.  */
>#define RTLD_GLOBAL 0x00100
>
>/* Unix98 demands the following flag which is the inverse to RTLD_GLOBAL.
>    The implementation does this by default and so we can define the
>    value to zero.  */
>#define RTLD_LOCAL  0
>
>/* Do not delete object when closed.  */
>#define RTLD_NODELETE 0x01000
>The first of all, I have added followed codes in function:
>PyMODINIT_FUNC init_ctypes(void) {...} in _ctypes.c file.
>
>     /* add RTLD_LAZY and RTLD_NOW definitions*/
>     PyModule_AddObject(m, "RTLD_LAZY", PyInt_FromLong(RTLD_LAZY));
>     PyModule_AddObject(m, "RTLD_NOW", PyInt_FromLong(RTLD_NOW));
>
>So, Is there anybody know how the CDLL can accept mode flag:RTLD_LAZY?

It's a known open bug.
https://bugs.python.org/issue20276

Some people who have really needed to get this to work with ctypes have
modified the source for ctypes as discribed here:
http://osdir.com/ml/python.ctypes/2006-10/msg00029.html

I just stopped using ctypes and use cffi instead.
https://cffi.readthedocs.org/en/latest/

Laura



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