Python: More Nullptr Checks (#2574)

* Python: More Nullptr Checks

I am debugging a couple of crashes while mitigating CI.
One of them pointed to the locations here
(`ValueError: NULL pointer access`), so I decided to add some checks.

* Skip invalid tiles

* Skip Empty Tiles But Check Pointer

* Python: nullptr check in _array1d_from_pointer

Make the methods `get_particle_structs` and
`get_particle_boundary_buffer_structs` more robust.

1 files changed, 18 insertions, 0 deletions

diff --git a/Python/pywarpx/_libwarpx.py b/Python/pywarpx/_libwarpx.py
index 9ebbd262f..d80a1915f 100755
--- a/Python/pywarpx/_libwarpx.py
+++ b/Python/pywarpx/_libwarpx.py
@@ -136,6 +136,8 @@ _LP_LP_c_char = ctypes.POINTER(_LP_c_char)
 
 # this is a function for converting a ctypes pointer to a numpy array
 def _array1d_from_pointer(pointer, dtype, size):
+    if not pointer:
+        raise Exception(f'_array1d_from_pointer: pointer is a nullptr')
     if sys.version_info.major >= 3:
         # from where do I import these? this might only work for CPython...
         #PyBuf_READ  = 0x100
@@ -559,6 +561,8 @@ def get_particle_structs(species_name, level):
 
     particle_data = []
     for i in range(num_tiles.value):
+        if particles_per_tile[i] == 0:
+            continue
         arr = _array1d_from_pointer(data[i], _p_dtype, particles_per_tile[i])
         particle_data.append(arr)
 
@@ -599,6 +603,10 @@ def get_particle_arrays(species_name, comp_name, level):
 
     particle_data = []
     for i in range(num_tiles.value):
+        if particles_per_tile[i] == 0:
+            continue
+        if not data[i]:
+            raise Exception(f'get_particle_arrays: data[i] for i={i} was not initialized')
         arr = np.ctypeslib.as_array(data[i], (particles_per_tile[i],))
         try:
             # This fails on some versions of numpy
@@ -896,6 +904,8 @@ def get_particle_boundary_buffer_structs(species_name, boundary, level):
 
     particle_data = []
     for i in range(num_tiles.value):
+        if particles_per_tile[i] == 0:
+            continue
         arr = _array1d_from_pointer(data[i], _p_dtype, particles_per_tile[i])
         particle_data.append(arr)
 
@@ -949,6 +959,10 @@ def get_particle_boundary_buffer(species_name, boundary, comp_name, level):
 
     particle_data = []
     for i in range(num_tiles.value):
+        if particles_per_tile[i] == 0:
+            continue
+        if not data[i]:
+            raise Exception(f'get_particle_arrays: data[i] for i={i} was not initialized')
         arr = np.ctypeslib.as_array(data[i], (particles_per_tile[i],))
         try:
             # This fails on some versions of numpy
@@ -989,6 +1003,10 @@ def _get_mesh_field_list(warpx_func, level, direction, include_ghosts):
     for i in range(size.value):
         shape = tuple([shapes[shapesize*i + d] for d in range(shapesize)])
         # --- The data is stored in Fortran order, hence shape is reversed and a transpose is taken.
+        if shape[::-1] == 0:
+            continue
+        if not data[i]:
+            raise Exception(f'get_particle_arrays: data[i] for i={i} was not initialized')
         arr = np.ctypeslib.as_array(data[i], shape[::-1]).T
         try:
             # This fails on some versions of numpy