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Programs cannot safely rely on the order of evaluation of operands between sequence points. In this non-compliant code example, the order of evaluation of the operands to the {+} operator are unspecified.
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func(i++, i); |
The call to func() has undefined behavior because there are no sequence points between the argument expressions. The first (left) argument expression reads the value of i (to determine the value to be stored) and then modifies i. The second (right) argument expression reads the value of i between the same pair of sequence points as the first argument, but not to determine the value to be stored in i. This additional attempt to read the value of i has undefined behavior.
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