ContextImpl::currentContext contains a reference to one of the
DeviceInfoImpl objects from:
static std::vector<DeviceInfoImpl> global_devices;
ContextImpl::currentContext is destroyed in the destructor
for the statically defined object __module, and relies on its
DeviceInfoImpl reference to query some hardware features while
being destroyed.
This means that we need to ensure that the global_devices vector is
destroyed affter __module, otherwise ContextImpl::currentContext's
DeviceInfoImpl reference will no longer be valid when __module is
destroyed.
Since these variables are all confined to a single compilation unit,
they will be destruct from bottom to top, so we need to make sure
that __module is the bottom definition so it can be destroyed first.
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