Re: Is the behavior unspecified or can it the expression be evaluated?

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 25 Sep 2008 01:30:01 -0700 (PDT)
Message-ID:
<7fd72d0a-a69c-4fc1-82b1-4493a75a4ce6@a70g2000hsh.googlegroups.com>
On Sep 24, 10:29 pm, Victor Bazarov <v.Abaza...@comAcast.net> wrote:

coolguyaround...@gmail.com wrote:

Here, analyse this snippet :


    [...]

I tried this in 2 compilers and the result was same, but the
result of the following in the same 2 compilers was
different:

{
int a=1;
std::cout<<a<<++a;...........Statement 1
a=1;
std::cout<<a<<a++;...........Statement 2
}

Any reasons for such behavior in this case and also for the
behavior in the former code??


Here the behaviour is unspecified because it depends on the
order of evaluation of the function arguments, which itself is
unspecified. It is not undefined, though.


Yes it is. There's still no sequence point between the read of
a in the first sub-expression, and the modification in the
second. A function call introduces a sequence point, but
there's nothing here that would require the operator<< function
to be called between those sub-expressions.

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