What is an ABI, and Why is Breaking it Bad?
summary
ABI means the platform-level binary contract: parameter passing, object layout, vtable layout, exception and symbol semantics. Examples include adding/removing struct fields (size/offset mismatch), inserting virtual functions (vtable slot shift), the std::string COW change that forced incompatible layouts, and the subtle std::pair trivial copy change that moves some specializations from stack to register. Breaks usually appear only at runtime, require full rebuilds or fat binaries, and are mitigated by symbol versioning, inline-namespace schemes, or ABI-checking tools like libabigail.
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chapters (10)
- 0:00Introduction and speaker background
- 1:34What is an ABI
- 4:01ODR violations and ABI breaks
- 13:43Virtual function table changes
- 20:26From ODR to ABI breaks
- 23:56Real-world ABI break examples
- 34:12Why ABI breaks matter to standards
- 41:01Detecting ABI breaks
- 50:01Impact on developers and users
- 1:05:20Q&A
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