Added lib_from_sym to detect openmp conflict and proper threading lay…

…er default value

numba/_helpermod.c

@@ -8,6 +8,12 @@ Expose all functions as pointers in a dedicated C extension.
 /* Import _pymodule.h first, for a recent _POSIX_C_SOURCE */
 #include "_pymodule.h"
 #include <math.h>
+#ifdef __linux__
+#define _GNU_SOURCE 1
+#include <dlfcn.h>
+#include <string.h>
+#undef _GNU_SOURCE
+#endif
 #ifdef _MSC_VER
     #define false 0
     #define true 1
@@ -160,6 +166,33 @@ build_npymath_exports_dict(void)
     return dct;
 }
 
+static PyObject *
+_numba_lib_from_sym(PyObject *m, PyObject *arg)
+{
+    void *sym;
+    Dl_info di;
+    PyObject *ret = NULL;
+    assert(arg);
+#ifdef __linux__
+    /* Treat arg as a borrowed reference. */
+    Py_INCREF(arg);
+
+    sym = dlsym(RTLD_DEFAULT, PyString_AsString(arg));
+    if(sym) {
+        if(dladdr(sym, &di))
+            ret = PyString_FromString(di.dli_fname);
+        else
+            ret = PyString_FromString("(unknown)");
+    }
+
+    /* Treat arg as a borrowed reference. */
+    Py_DECREF(arg);
+    if(ret)
+        return ret;
+#endif
+    Py_RETURN_NONE;
+}
+
 static PyMethodDef ext_methods[] = {
     { "rnd_get_state", (PyCFunction) _numba_rnd_get_state, METH_O, NULL },
     { "rnd_get_py_state_ptr", (PyCFunction) _numba_rnd_get_py_state_ptr, METH_NOARGS, NULL },
@@ -168,6 +201,7 @@ static PyMethodDef ext_methods[] = {
     { "rnd_set_state", (PyCFunction) _numba_rnd_set_state, METH_VARARGS, NULL },
     { "rnd_shuffle", (PyCFunction) _numba_rnd_shuffle, METH_O, NULL },
     { "_import_cython_function", (PyCFunction) _numba_import_cython_function, METH_VARARGS, NULL },
+    { "lib_from_sym", (PyCFunction) _numba_lib_from_sym, METH_O, NULL },
     { NULL },
 };