[Fix] Checking nullptr on Node.cpp and ConstantFolding.cpp

Context

In the context of using expand_metaops(), adapt_to_backend() and constant_folding() to export arm_cortex_m with the LibCMSIS_NN backend, I encountered SIGSEGV when using two expand_metaops() or two constant_folding() in a row.

Example

model = aidge_core.sequential([
    aidge_core.Conv2D(in_channels=2, out_channels = 2, kernel_dims = [1,1], name = 'conv', stride_dims= [1, 1], dilation_dims = [1, 1], no_bias= False),
    aidge_quantization.Quantizer(scalingFactor = 0.005, clip_min = -128.0, clip_max = 127.0, name="scale")
    
])


model.set_datatype(aidge_core.dtype.float32)
model.set_backend("cpu")

model.save("PreFuse")
print("Fuse ConvScaling")

aidge_core.fuse_to_metaops(model, "Conv2D->Quantizer", "PaddedConvScalingRelu")
model.compile('cpu',aidge_core.dtype.float32, dims=[input_dims])

model.save("PostFuse")


scheduler = aidge_core.SequentialScheduler(model)
scheduler.generate_scheduling()

from aidge_export_arm_cortexm.export_registry import ExportLibAidgeARM, ExportLibCMSISNN

for node in model.get_nodes():

    aidge_core.Log.debug(f"Setting backend {ExportLibCMSISNN._name} to {node.name()}[{node.type()}].")
    node.get_operator().set_backend(ExportLibCMSISNN._name)


aidge_core.adapt_to_backend(model)

model.save("adapt_to_backend")
aidge_core.constant_folding(model)
aidge_core.constant_folding(model)
model.save("constant_folding")

# aidge_core.remove_constantOfShape(model)

aidge_core.expand_metaops(model)
aidge_core.expand_metaops(model)

model.save("exploded")
print("print")

Modified files

• Node.cpp and ConstantFolding.cpp, nullptr methods can no longer be accessed ;

Observations

With this MR, nullptr methods can no longer be accessed, but the problems may come from the calling functions.

src/graph/Node.cpp

@@ -390,7 +390,8 @@ void Aidge::Node::resetConnections(bool includeLearnableParam) {
     }
     for (IOIndex_t i = 0; i < nbOutputs(); ++i) {
         for (std::pair<std::shared_ptr<Node>, IOIndex_t> child : output(i)) {
-            child.first->removeParent(child.second);
+            if(child.first != nullptr && child.first->getParents().size() > 0) child.first->removeParent(child.second);
+            else Log::debug("No child.first");
         }
         mChildren[i] = std::vector<std::weak_ptr<Node>>();
         mIdInChildren[i] = std::vector<IOIndex_t>();

[Cyril Moineau]

Debug log is unecessary.

child.first->getParents().size() > 0 check is weird, you are in the parent node you get the output and then check that the output has a parent?

-            if(child.first != nullptr && child.first->getParents().size() > 0) child.first->removeParent(child.second);
-            else Log::debug("No child.first");
+            if(child.first != nullptr) child.first->removeParent(child.second);

[Wissam Boussella]

i was looking for a boolean method to do child.first->exists(child.second)

[Cyril Moineau]

Ok but still the check is weird, you are in the parent so it not null.