MISRA CPP 2008, order of evaluation

Asked Jun 20 '17 at 08:52

Active Jun 20 '17 at 08:52

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While reading MISRA CPP 2008, I have stumbled upon the following example:

x = b[i] + i++;

this example shows that order of evaluation can affect result, and there is undefined behavior due to 2 ways are possible:

1.b[i] then i++
2.i++ then b[i]

as far as I remember from CS courses - i will be incremented only after the whole expression evaluation, is that true?
If so could you please provide me with the reference to relevant info in the standard?

asked Jun 20 '17 at 08:52

spin_eight

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It is not UB because of 2 possible evaluation orders (that would be *unspecified behaviour*). It is UB because there's no sequence point between modifying and reading `i`. – juanchopanza Jun 20 '17 at 08:53
*"is that true?"* - No, it is not. – StoryTeller - Unslander Monica Jun 20 '17 at 08:55
i++ will: fetch i and save it for later, increment i, return the saved value from before. This may happen before b[i] is evaluated – Paolo Brandoli Jun 20 '17 at 08:57
C++ Standard: Have a look at 4.6.17 (C alike, by the way, 6.5.2...). – Aconcagua Jun 20 '17 at 09:33

MISRA CPP 2008, order of evaluation

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