[PATCH][StaticAnalyzer] new check comparing equal expression

[Daniel Marjamäki]

Hi Jordan!

> Even though this actually does something ("++x == ++x"), it's not well-defined anyway (specifically, either one could go first), so I'd still like to catch this as a copy-paste error. What do you think?

Yes this is true now as we are only checking comparison operators. However:

1. When we extend it to && and || operators we must be more careful about this. We can of course add logic later that avoids increment only if the top operator is && or ||.

2. I think it would be interesting to add new diagnostics about undefined execution order. Then we will warn about ("++x == ++x") with a stronger warning message that complains about undefined behaviour. 

Best regards,
Daniel Marjamäki

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Daniel Marjamäki Senior Engineer
Evidente ES East AB  Warfvinges väg 34  SE-112 51 Stockholm  Sweden

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