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Type-appropriate null representation

Always use type-appropriate mechanisms to represent the absence of a value. For objects, use default constructors rather than nullptr. For potentially absent values, consider using optional types. For pointers, use null checks before performing operations on them.

raw .md Null Handling C++

Always use type-appropriate mechanisms to represent the absence of a value. For objects, use default constructors rather than nullptr. For potentially absent values, consider using optional types. For pointers, use null checks before performing operations on them.

Examples:

  • INCORRECT: bias_md = nullptr; when bias_md is an object type (dnnl::memory::desc)

  • CORRECT: bias_md = dnnl::memory::desc(); to represent an “empty” descriptor

  • INCORRECT: ncclHeartbeatMonitorThread_ = std::thread(...); without checking current state
  • CORRECT: 
    // Check nullness before assignment to prevent issues on second call
if (!ncclHeartbeatMonitorThread_.joinable()) {
ncclHeartbeatMonitorThread_ = std::thread(...);
}

This practice improves type safety, prevents null pointer dereferences, and creates more maintainable code by using language features designed for representing absence of values.