Unverified Commit 6bcc263b authored by Richard Berger's avatar Richard Berger
Browse files

Ensure LAMMPS pointer is of type c_void_p 

Fixes segfaults caused by API change. The API change in
lammps_open and lammps_open_no_mpi makes them return the LAMMPS pointer
via their return value. However due to how ctypes operates, even
if restype is specified to be c_void_p, the function returns an integer.

Without the proper type of the pointer, calling functions without arglists would default
to using 32bit integers to pass an argument, which cuts away parts of the 64bit pointer.
Subsequently, resolving the truncated pointer in the library causes segfaults.

This commit fixes the root cause. But it also highlights the need of specifying
the arglists of all library functions.
parent caeb0af0

python/lammps.py

+3 −3
Original line number Diff line number Diff line
@@ -340,7 +340,7 @@ class lammps(object): 
        self.opened = 1

        comm_ptr = self.MPI._addressof(comm)

        comm_val = MPI_Comm.from_address(comm_ptr)

        self.lmp = self.lib.lammps_open(narg,cargs,comm_val,None)

        self.lmp = c_void_p(self.lib.lammps_open(narg,cargs,comm_val,None))



      else:

        if self.has_mpi4py and self.has_mpi_support:
@@ -355,10 +355,10 @@ class lammps(object): 
          cargs = (c_char_p*narg)(*cmdargs)

          self.lib.lammps_open_no_mpi.argtypes = [c_int, c_char_p*narg, \

                                                  c_void_p]

          self.lmp = self.lib.lammps_open_no_mpi(narg,cargs,None)

          self.lmp = c_void_p(self.lib.lammps_open_no_mpi(narg,cargs,None))

        else:

          self.lib.lammps_open_no_mpi.argtypes = [c_int, c_char_p, c_void_p]

          self.lmp = self.lib.lammps_open_no_mpi(0,None,None)

          self.lmp = c_void_p(self.lib.lammps_open_no_mpi(0,None,None))



    else:

      # magic to convert ptr to ctypes ptr

unittest/python/python-numpy.py

+4 −0
Original line number Diff line number Diff line 
import sys,os,unittest

from lammps import lammps, LMP_STYLE_GLOBAL, LMP_STYLE_ATOM, LMP_TYPE_VECTOR, LMP_TYPE_SCALAR

from ctypes import c_void_p



class PythonNumpy(unittest.TestCase):

    def setUp(self):
@@ -11,6 +12,9 @@ class PythonNumpy(unittest.TestCase): 
    def tearDown(self):

        del self.lmp



    def testLammpsPointer(self):

        self.assertEqual(type(self.lmp.lmp), c_void_p)



    def testExtractCompute(self):

        self.lmp.command("region       box block 0 2 0 2 0 2")

        self.lmp.command("create_box 1 box")

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