<< Extended one-definition rule >>

• Such inconsistencies are rare, but may happen.
• C++'s one-definition rule requires that if two compilation units see definitions of the "same" name, they must be token-by-token equivalent.
• "Extended one-definition rule":
  In a "well-behaved program" -
  • a shared definition is defined in a single location in a header file;
  • the "meaning" of that definition does not change between compilation units.
• We optimize for this assumption, but must tolerate violations.
• Bonus: Can warn about violations, which are probably unintended.