Code crashes at runtime - is this valid c++

[chrisstankevitz]

Compile with:
g++ crash.cpp -O2

Crashes on:
g++ (Gentoo 4.3.2 p1.1) 4.3.2
g++ (GCC) 4.3.0 20080428 (Red Hat 4.3.0-8)
g++ (ubuntu current stable)

Steps to reproduce:
1. Make a file crash.cpp (contents below)
2. g++ crash.cpp -O2
3. ./a.out
Floating point exception

Source:

#include <iostream>
#include <fenv.h>

float g(const float& x)
{
float y = x;
if(y == 0.0f)
{
y=1.0f;
}
return x/y;
}

void f(const float &z)
{
if (z 0.0f)
{
float Unit2 = g(z);

std::cout << Unit2;
}
}

int main()
{
feenableexcept( FE_INVALID);

float a = 130.0f;
f(a);

return 0;
}

[Thomas J. Gritzan]

[about comparing floating point numbers]

James Kanze wrote:

On Nov 6, 11:22 pm, Salt_Peter <pj_h...@yahoo. comwrote:

>the following is expected...

>#include <iostream>

>int main()
{
float fa(0.0f);
float fb(0.0f);

> if( fa == fb)
std::cout << "not equal\n";
else
std::cout << "equal\n";

"==": not equal,
"!=": equal?

I'll case that as typing error. ;-)

> std::cout << "Press ENTER to EXIT.\n";
std::cin.get();
}

>/*
not equal
*/

Are you kidding? Any compiler which outputs "not equal" with
that program is seriously broken.

I disagree. Any compiler outputting "equal" with this program is broken.

But trying to prove something with a wrong program is broken, too.

--
Thomas

[Pete Becker]

On 2008-11-07 09:31:43 -0500, "Thomas J. Gritzan"
<ph************ *@gmx.desaid:

[about comparing floating point numbers]

James Kanze wrote:

>On Nov 6, 11:22 pm, Salt_Peter <pj_h...@yahoo. comwrote:

>>the following is expected...

>>#include <iostream>

>>int main()
{
float fa(0.0f);
float fb(0.0f);

>>if( fa == fb)
std::cout << "not equal\n";
else
std::cout << "equal\n";

"==": not equal,
"!=": equal?

I'll case that as typing error. ;-)

>>std::cout << "Press ENTER to EXIT.\n";
std::cin.get( );
}

>>/*
not equal
*/

Are you kidding? Any compiler which outputs "not equal" with
that program is seriously broken.

I disagree. Any compiler outputting "equal" with this program is broken.

Good catch. Fake results.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)

[Rolf Magnus]

ch************* @gmail.com wrote:

>
Crashes on:
g++ (Gentoo 4.3.2 p1.1) 4.3.2
g++ (GCC) 4.3.0 20080428 (Red Hat 4.3.0-8)
g++ (Ubuntu 4.3.2-1ubuntu11) 4.3.2 (my machine, but maybe not Rolf's)

I tried it with -O2. No crash with the very same compiler version.

PS: Rolf, sorry for calling you Peter earlier.

No problem. I think I'll live ;-)

[chrisstankevitz]

On Nov 7, 11:03*am, Rolf Magnus <[e-mail]:

I tried it with -O2. No crash with the very same compiler version.

Looks like it's a problem with 64 bit only. I also don't have a
problem on 32 bit.

Rolf, are you running 32 or 64 bit?

I filed a bug and it was closed fixed in 4.3.3

Chris

[James Kanze]

On Nov 8, 12:28*am, chrisstankev... @gmail.com wrote:

On Nov 7, 11:03*am, Rolf Magnus <[e-mail]:

I tried it with -O2. No crash with the very same compiler
version.

Looks like it's a problem with 64 bit only. *I also don't have
a problem on 32 bit.

Rolf, are you running 32 or 64 bit?

I just tried it in 64 bit with g++ 4.2.1 (under Suse Linux, with
the 2.6.22 kernel). No problems.

--
James Kanze (GABI Software) email:ja******* **@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
9 place Sémard, 78210 St.-Cyr-l'École, France, [phone]

[Rolf Magnus]

ch************* @gmail.com wrote:

On Nov 7, 11:03 am, Rolf Magnus <[e-mail]:

>I tried it with -O2. No crash with the very same compiler version.

Looks like it's a problem with 64 bit only. I also don't have a
problem on 32 bit.

Rolf, are you running 32 or 64 bit?

I'm running 32 bit.