Garbage In, Garbage Out: Arguing about Undefined Behavior...
summary
Argues that undefined behavior is a symptom not the root problem and proposes treating language features as either narrow vs wide contracts with concrete principles: a narrow contract must be checkable, provide significant value, be explainable, and not break long‑standing code. Shows concrete examples (null dereference, signed left shifts, unsigned wrap causing allocation bugs in SPEC, a Bzip inner loop where signed vs unsigned changes 2x performance), points to Android and WebAssembly tradeoffs and recommends targeted runtime/static checks rather than blanket redefinition.
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chapters (19)
- 0:00Introduction
- 5:30Undefined Behavior
- 8:10Programming Errors
- 11:30Symptoms of Undefined Behavior
- 12:37Wide vs Narrow Contracts
- 15:07What can we do
- 16:30Can we define all behaviors
- 17:25What are the tradeoffs
- 17:42Can we constrain undefined behavior
- 18:12This isnt about undefined behavior
- 18:41The wishywashy thing
- 19:30Narrow contracts
- 20:37Programming error
- 21:13Principles
- 24:25Examples
- 27:48Complicated Example
- 33:14Spec Example
- 39:17Optimization Example
- 44:07Questions
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