[LIP] Undefined behaviour ?

-----------------
#include <stdio.h>
main() {
int i = 4;
/* int j = i+++++i+i+++++i; */
/* int j = i++ + ++i + i++ + ++i ; */
int j = (i++)+(++i)+(i++)+(++i);
printf("%d\n", j);
}
-----------------

The above peice of code has three initialization of j out of which only
the last two works with gcc 3.2.2

I am not sure why gcc fails on the first but the error message "invalid
lvalue in increment" doesnt somehow seem right. I dont see the problem
with j and if i++ is being considered a lvalue then why so ?

After compillation I get a value of 21 - how that value is coming up I
have no idea. VC compiles all three syntaxes I believe but returns 21
in debug mode and 24 in release mode.

From my limited knowledge I can think of two ways to process the
expression.

(i++) + (++i) + (i++) + (++i) = (4++) + (++5) + (6++) + (++7) = 4 + 6 +
6 + 8 = 24

(i++) + (++i) + (i++) + (++i) = (4++) + (++4) + (5++) + (++5) = 4 + 5 +
5 + 6 = 20

Obviously none of them match what gcc is coming up with. Could someone
please explain what is happening here ?



Mithun

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