order of evaluation

[ASobol]

//code.begin()
#include <iostream>

int g (int i)
{
static const int j = i;
return j;
}

int main (int, char**)
{
std::cout << g(0) << g(1) << g (2) << g(3);
return 0;
}
//code.end()

Is output of this program undefined due to C++ standart?
Compilers i have access to (msvc 7.1 and gcc 3.3) both produce "3333"
output.


--Sasha

 

[Sumit Rajan]

//code.begin()
#include <iostream>

int g (int i)
{
static const int j = i;
return j;
}

int main (int, char**)
{
std::cout << g(0) << g(1) << g (2) << g(3);

The compiler is allowed to determine the order in which the 4 calls to g()
are executed.

return 0;
}

//code.end()

Is output of this program undefined due to C++ standart?

Undefined behaviour. See:
http://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-38.16
http://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-38.15
http://www.langer.camelot.de/Articles/VSJ/SequencePoints/SequencePoints.html



Regards,
Sumit.

 

[msalters]

The compiler is allowed to determine the order in which the 4 calls to g()
are executed.

Yes, but it may not execute them concurrently (unless you cannot detect
it, of course. "as if"-rule ). One call must be made first. It may be a
different choice on every run, though.

Undefined behaviour.

Wrong, unspecified. There are proper sequence points between the
calls, the only thing unspecified is the order of sequence points.
No variable is modified twice between sequence points. In fact,
the only variable modified is static const int j, which by
definition cannot be modified twice at all.

Regards,
Michiel Salters

 

[Sumit Rajan]

Wrong, unspecified.

You're right. Thanks for pointing that out.

Regards,
Sumit.