difference in execution turbo and visual

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Could anyone explain these undefined behaviors (i = i++ + ++i , i = i++, etc…)

Consider, following 2 coding lines in C

int a=0;

printf("%d%d%d%d",++a,a+1,a++,++a);

in visual C++, it gives

output:3431

But in Turbo C++ gives:

output:3311

This is also compiler dependent?

Order of evaluation in the absence of sequence points is [unspecified behavior](http://en.wikipedia.org/wiki/Unspecified_behavior). — Sergey Kalinichenko, Feb 24 '12 at 16:28
This is answered by an entry of the [C++ SO FAQ](http://loungecpp.wikidot.com/faq#toc11) — Seth Carnegie, Feb 24 '12 at 16:31
@LuchianGrigore only as the comma operator, not as the separator of function arguments. — Daniel Fischer, Feb 24 '12 at 16:42
@LuchianGrigore Nor as the separator for variable declarations, by the way. Yes, there's a difference between these. — Daniel Fischer, Feb 24 '12 at 16:46

score 2 · Accepted Answer · answered Feb 24 '12 at 16:26

2

The C specification does not specify the order that the arguments to your function will be evaluated, so there's no guarantee what output you will get.

answered Feb 24 '12 at 16:26

Gabe

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It's not just that the output isn't guaranteed. He's modified `a` more than once between sequence points, which leads to undefined behavior. Therefore it's not just a matter of "could be 3 or 4", but could also include "formats the hard disk", "blows up the machine", or essentially anything else. – Jerry Coffin Feb 24 '12 at 17:28

difference in execution turbo and visual

1 Answers1