A question for C++ expert on ++a and a++

Quote:

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Originally Posted by TheCPUWizard

Code:

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if ((ptr) && (ptr->MethodIO))
{
}

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i always make code like this:

Code:

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if (ptr)
if(ptr->MethodIO)
{
}

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i dont think its any diffrent..

however the evaluation stops at ptr, is this defined behavior by the standards?

The standard guarantees that the right-hand-side of && will not be evaluated if the left-hand side of && is false. Also the right-hand-side of || will not be evaluated if the left-hand side of && is true.

But if && or || is overloaded, that guarantee is lost because both sides need to be evaluated before operator&& or operator|| can be called, I think.

Quote:

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Originally Posted by exterminator

Did you read any of the posts in this thread above before posting?

//Btw a similar issue came up on clc++m recently - http://groups.google.co.uk/group/com...b9275faa0ec230

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the link provided by exterminator explain one more factor, a++ and ++a can be evaluated at the same time, which can mess up the memory. :ehh: so maybe undefined behavior will be more correct than unspecified behavior.

Thanks!

Quote:

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Originally Posted by Mitsukai

however the evaluation stops at ptr, is this defined behavior by the standards?

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Yes, it is.

Code:

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5.14 Logical AND operator [expr.log.and]

logical-and-expression:
        inclusive-or-expression
        logical-and-expression && inclusive-or-expression

1 The && operator groups left-to-right. The operands are both implicitly
converted to type bool (clause 4). The result is true if both operands are
true and false otherwise. Unlike &, && guarantees left-to-right evaluation:
the second operand is not evaluated if the first operand is false.

2 The result is a bool. All side effects of the first expression except for
destruction of temporaries (12.2) happen before the second expression is evaluated.

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&& also is a sequence point.