Is it a Bug in g++ compiler`s -O flag??

nikhil_dokania's Avatar, Join Date: Oct 2006
Newbie Member
The output is different for the following two codes when compiled as : "g++ -O foo.cpp"
1st COde :
Code:
#include<iostream.h>
#include<math.h>
int main(){
	double d=log(8)/log(2);
	cout<<"d="<<d<<"\t floor(d)="<<floor(d);        //<<"\t"<<floor(10.0)<<"\n";
	return 0;
}
------------------------------------------------------------------------------------------------------------------
2nd COde :
Code:
#include<iostream.h>
#include<math.h>
int main(){
	double d=log(8)/log(2);
	cout<<"d="<<d<<"\t floor(d)="<<floor(d)<<"\t"<<floor(10.0)<<"\n";
	return 0;
}
---------------------------------------------------------------------------------------------------------------

Expected output : d=3 floor(d)=3 10
But The First code give : d=3 floor(d)=2 10
while the second gives the right output.
Could nyone plz explain whats going wrong!!

Nikhil

Last edited by shabbir; 17Oct2006 at 10:12.. Reason: Code formating.
0
shabbir's Avatar, Join Date: Jul 2004
Go4Expert Founder
Quote:
Originally Posted by nikhil_dokania
Expected output : d=3 floor(d)=3 10
Nope. Its should be d=3 floor(d)=2 10 because log(8)/log(2) = 2.999999..... and so floor should be 2.

I guess the difference in output should be a bug as far as I think.
0
nikhil_dokania's Avatar, Join Date: Oct 2006
Newbie Member
i think u r right. and thanx for replying. But the difference in output is not recognized as a Compiler bug. I jus learned it from this GCC website. Check it out: http://gcc.gnu.org/bugs.html#nonbugs_general