CppCon 2016: Chandler Carruth “Garbage In, Garbage Out: Arguing about Undefined Behavior..."

What people said

moefh · 2023-08 · Recommendation

One man's "broken code produced by the compiler" is another man's "excellently optimized code by the compiler". Where to draw the line is not always clear, but here's a very clear-cut example[1] where emitting a warning would be bad. If you don't want to watch the video, it's basically this: - the code technically contains undefined behavior, but it will never be actually triggered by the program - changing the code to remove undefined behavior forces the compiler to emit terrible code Making the compiler yell at the programmer in this case would be terrible, but it's clearly a consequence of what you're asking. [1] [VIDEO]

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Joky · 2018-11 · Recommendation

Actually I discourage my colleague to use unsigned especially because they can overflow. The problem with overflow is that most of the time it is a program bug if there is an overflow that wasn't intended. Using signed arithmetic means that you can actually trap on overflow and catch these bugs (using fuzzing for instance). Chandler explained it nicely in his CPPCon 2016 talk "Garbage In, Garbage Out: Arguing about Undefined Behavior...". I encourage to watch the full talk but here is one relevant example: [VIDEO] And here he mentions how Google experimented with this internally: [VIDEO]

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lyricaljoke · 2018-05 · Recommendation

Chandler Carruth's talk on the subject was really useful for my own understanding of the reasoning behind UB: [VIDEO]

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