"C" the intracacies

The other day, one of my nerdy mates, Rajdeep had put forth this problem, which caught me on the back foot. Apparently, the problem appealed like a fundamental predict the output snippet, but the exact reasoning is yet to be found. Following is the code snippet with some steps, someone needs the explain the reason behind such a weird output.

//File name: googly.c
#include
int main()
{
int a,b;
a=((b=5)+1); //Line 2
printf("a=%d b=%d",a,b);
return 0;
}

As you would have expected Line 2 essentially reduces to two sequential statements, b=5 and then a=b+1 and you get the result 'a'=6 and 'b'=5;

Now try replacing Line 2 with the expression a=((b=5)++)and then try to compile using a standard C compiler and you would observe an compilation error. You might come across a logic to explain that error.

But the strange behavior doesn't end here, save the code with a .cpp extension, compile it with a standard C++ compiler & you'd be startled to note that the error is gone and the program runs seamlessly to produce the output as a='5' and b='6'.

I suppose there's some compilation issue that makes it happen, but need a succinct logical explanation to this. Your reasonings are awaited...

Read more...