• Nick Coghlan's avatar
    PEP 489: Multi-phase extension module initialization · d5cacbb1
    Nick Coghlan yazdı
    Known limitations of the current implementation:
    
    - documentation changes are incomplete
    - there's a reference leak I haven't tracked down yet
    
    The leak is most visible by running:
    
      ./python -m test -R3:3 test_importlib
    
    However, you can also see it by running:
    
      ./python -X showrefcount
    
    Importing the array or _testmultiphase modules, and
    then deleting them from both sys.modules and the local
    namespace shows significant increases in the total
    number of active references each cycle. By contrast,
    with _testcapi (which continues to use single-phase
    initialisation) the global refcounts stabilise after
    a couple of cycles.
    d5cacbb1
dynload_shlib.c 3.28 KB

/* Support for dynamic loading of extension modules */

#include "Python.h"
#include "importdl.h"

#include <sys/types.h>
#include <sys/stat.h>

#if defined(__NetBSD__)
#include <sys/param.h>
#if (NetBSD < 199712)
#include <nlist.h>
#include <link.h>
#define dlerror() "error in dynamic linking"
#endif
#endif /* NetBSD */

#ifdef HAVE_DLFCN_H
#include <dlfcn.h>
#endif

#if (defined(__OpenBSD__) || defined(__NetBSD__)) && !defined(__ELF__)
#define LEAD_UNDERSCORE "_"
#else
#define LEAD_UNDERSCORE ""
#endif

/* The .so extension module ABI tag, supplied by the Makefile via
   Makefile.pre.in and configure.  This is used to discriminate between
   incompatible .so files so that extensions for different Python builds can
   live in the same directory.  E.g. foomodule.cpython-32.so
*/

const char *_PyImport_DynLoadFiletab[] = {
#ifdef __CYGWIN__
    ".dll",
#else  /* !__CYGWIN__ */
    "." SOABI ".so",
    ".abi" PYTHON_ABI_STRING ".so",
    ".so",
#endif  /* __CYGWIN__ */
    NULL,
};

static struct {
    dev_t dev;
    ino_t ino;
    void *handle;
} handles[128];
static int nhandles = 0;


dl_funcptr
_PyImport_FindSharedFuncptr(const char *prefix,
                            const char *shortname,
                            const char *pathname, FILE *fp)
{
    dl_funcptr p;
    void *handle;
    char funcname[258];
    char pathbuf[260];
    int dlopenflags=0;

    if (strchr(pathname, '/') == NULL) {
        /* Prefix bare filename with "./" */
        PyOS_snprintf(pathbuf, sizeof(pathbuf), "./%-.255s", pathname);
        pathname = pathbuf;
    }

    PyOS_snprintf(funcname, sizeof(funcname),
                  LEAD_UNDERSCORE "%.20s_%.200s", prefix, shortname);

    if (fp != NULL) {
        int i;
        struct _Py_stat_struct status;
        if (_Py_fstat(fileno(fp), &status) == -1)
            return NULL;
        for (i = 0; i < nhandles; i++) {
            if (status.st_dev == handles[i].dev &&
                status.st_ino == handles[i].ino) {
                p = (dl_funcptr) dlsym(handles[i].handle,
                                       funcname);
                return p;
            }
        }
        if (nhandles < 128) {
            handles[nhandles].dev = status.st_dev;
            handles[nhandles].ino = status.st_ino;
        }
    }

    dlopenflags = PyThreadState_GET()->interp->dlopenflags;

    handle = dlopen(pathname, dlopenflags);

    if (handle == NULL) {
        PyObject *mod_name;
        PyObject *path;
        PyObject *error_ob;
        const char *error = dlerror();
        if (error == NULL)
            error = "unknown dlopen() error";
        error_ob = PyUnicode_FromString(error);
        if (error_ob == NULL)
            return NULL;
        mod_name = PyUnicode_FromString(shortname);
        if (mod_name == NULL) {
            Py_DECREF(error_ob);
            return NULL;
        }
        path = PyUnicode_FromString(pathname);
        if (path == NULL) {
            Py_DECREF(error_ob);
            Py_DECREF(mod_name);
            return NULL;
        }
        PyErr_SetImportError(error_ob, mod_name, path);
        Py_DECREF(error_ob);
        Py_DECREF(mod_name);
        Py_DECREF(path);
        return NULL;
    }
    if (fp != NULL && nhandles < 128)
        handles[nhandles++].handle = handle;
    p = (dl_funcptr) dlsym(handle, funcname);
    return p;
}