Resolve "warning: copying an object of non-trivial type"

[vzhurba01]

Today when building cuda.bindings there are two types of warnings and we should conclude on how they are to be handled.

1. dereferencing type-punned pointer will break strict-aliasing rules

cuda/bindings/_lib/cyruntime/utils.cpp: In function ‘cudaError_t __pyx_f_4cuda_8bindings_4_lib_9cyruntime_5utils_toDriverGraphNodeParams(const cudaGraphNodeParams*, CUgraphNodeParams*)’:
cuda/bindings/_lib/cyruntime/utils.cpp:41075:48: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
41075 |     (__pyx_v_driverParams[0]).extSemSignal = (((CUDA_EXT_SEM_SIGNAL_NODE_PARAMS_v2 *)(&__pyx_v_rtParams[0].extSemSignal))[0]);
      |                                               ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cuda/bindings/_lib/cyruntime/utils.cpp:41075:48: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
cuda/bindings/_lib/cyruntime/utils.cpp:41113:46: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
41113 |     (__pyx_v_driverParams[0]).extSemWait = (((CUDA_EXT_SEM_WAIT_NODE_PARAMS_v2 *)(&(__pyx_v_rtParams[0]).extSemWait))[0]);
      |                                             ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cuda/bindings/_lib/cyruntime/utils.cpp:41113:46: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]

2. copying an object of non-trivial type

cuda/bindings/runtime.cpp: In function ‘int __pyx_pf_4cuda_8bindings_7runtime_25cudaGraphKernelNodeUpdate_10updateData_2__set__(__pyx_obj_4cuda_8bindings_7runtime_cudaGraphKernelNodeUpdate*, __pyx_obj_4cuda_8bindings_7runtime_anon_union8*)’:
cuda/bindings/runtime.cpp:216214:16: warning: ‘void* memcpy(void*, const void*, size_t)’ copying an object of non-trivial type ‘union cudaGraphKernelNodeUpdate::<unnamed>’ from an array of ‘union __pyx_pf_4cuda_8bindings_7runtime_25cudaGraphKernelNodeUpdate_10updateData_2__set__(__pyx_obj_4cuda_8bindings_7runtime_cudaGraphKernelNodeUpdate*, __pyx_obj_4cuda_8bindings_7runtime_anon_union8*)::anon_union8’ [-Wclass-memaccess]
216214 |   (void)(memcpy((&(__pyx_v_self->_ptr[0]).updateData), ((union anon_union8 *)((__pyx_t_4cuda_8bindings_7runtime_void_ptr)__pyx_t_5)), (sizeof((__pyx_v_self->_ptr[0]).updateData))));
       |          ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from cuda/bindings/runtime.cpp:1248:
/usr/local/cuda-12.6/include/driver_types.h:3302:11: note: ‘union cudaGraphKernelNodeUpdate::<unnamed>’ declared here
 3302 |     union {
      |           ^

(1) We should ignore this because this is consistent with CUDA Runtime source and this file will be removed anyways in #100
(2) This one is tricky. What's happening is that we are trying to use memcpy on a type that has a non-trivial member (i.e. dim3). There's only one instance of this warning and we could do an simple WAR for this specific case:

diff --git a/cuda_bindings/cuda/bindings/runtime.pyx.in b/cuda_bindings/cuda/bindings/runtime.pyx.in
index e735ee4..0432d8e 100644
--- a/cuda_bindings/cuda/bindings/runtime.pyx.in
+++ b/cuda_bindings/cuda/bindings/runtime.pyx.in
@@ -12131,7 +12131,11 @@ cdef class cudaGraphKernelNodeUpdate:
         return self._updateData
     @updateData.setter
     def updateData(self, updateData not None : anon_union8):
-        string.memcpy(&self._ptr[0].updateData, <cyruntime.anon_union8*><void_ptr>updateData.getPtr(), sizeof(self._ptr[0].updateData))
+        self._ptr[0].updateData.gridDim.gridDim.x = updateData.gridDim.gridDim.x
+        self._ptr[0].updateData.gridDim.gridDim.y = updateData.gridDim.gridDim.y
+        self._ptr[0].updateData.gridDim.gridDim.z = updateData.gridDim.gridDim.z
+        string.memcpy(&self._ptr[0].updateData.param, <cyruntime.anon_struct19*><void_ptr>updateData.param.getPtr(), sizeof(self._ptr[0].updateData.param))
+        string.memcpy(&self._ptr[0].updateData.isEnabled, <unsigned int*><void_ptr>updateData.getPtr(), sizeof(self._ptr[0].updateData.isEnabled))
 {{endif}}
 {{if 'struct cudaLaunchMemSyncDomainMap_st' in found_types}}

What is tricky is how we should be approach these types of errors in the future. Worst case scenario is when you have a non-trivial type that's nested under many layers. Applying the same WAR in this multi-nested scenario would result in each Extension Type interacting with their members across multiple layers, is easier to make a mistake and updating the bindings generator is non-trivial.

A long term solution would perhaps have each Extension Type have a dedicated copy method.

For this issue I suggest we apply the WAR for this warning and any future warnings as long as they remain simple and are rare. The long term solution can be re-investigated when that is no longer the case.