Bad FP error with MS C++ compiler

[Adem24]

// MS-Bug # 999,995 (5 left for 1 million bugs :-) :

const double d = DBL_MIN;

double v00 = 0.0;
bool f00 = v00 d;

double v01 = 0.1;
bool f01 = v01 d;

gives wrongly 'false' for f00... :-)

[Alex Blekhman]

"Adem24" <ad****@adem24. org.invalidwrot e:

// MS-Bug # 999,995 (5 left for 1 million bugs :-) :

const double d = DBL_MIN;

double v00 = 0.0;
bool f00 = v00 d;

double v01 = 0.1;
bool f01 = v01 d;

gives wrongly 'false' for f00... :-)

The bug is in your code. DBL_MIN is a minimal positive value.

Alex

[Adem24]

"Adem24" wrote:

>
// MS-Bug # 999,995 (5 left for 1 million bugs :-) :

const double d = DBL_MIN;

double v00 = 0.0;
bool f00 = v00 d;

double v01 = 0.1;
bool f01 = v01 d;

gives wrongly 'false' for f00... :-)

Further analysis shows that it has nothing todo with the DBL_MIN
but the value ZERO !
Ie. the MS compiler treats the value 0 not correctly in FP ops.

[peter koch]

On 20 Jul., 16:10, "Adem24" <ade...@adem24. org.invalidwrot e:

// MS-Bug *# 999,995 (5 left for 1 million bugs :-) :

Or Adem24 bug# 3562?

>
* * * *const double d = DBL_MIN;

d is bigger than 0: perhaps it would help to read the documentation?

>
* * * *double v00 = 0.0;
* * * *bool * f00 = v00 d;

* * * *double v01 = 0.1;
* * * *bool * f01 = v01 d;

gives wrongly 'false' for f00... :-)

f00 should be true.

/Peter

[Victor Bazarov]

peter koch wrote:

On 20 Jul., 16:10, "Adem24" <ade...@adem24. org.invalidwrot e:

>// MS-Bug # 999,995 (5 left for 1 million bugs :-) :

Or Adem24 bug# 3562?

>>
const double d = DBL_MIN;

d is bigger than 0: perhaps it would help to read the documentation?

>>
double v00 = 0.0;
bool f00 = v00 d;

double v01 = 0.1;
bool f01 = v01 d;

gives wrongly 'false' for f00... :-)

f00 should be true.

REALLY? Should it? What's DBL_MIN, by definition? Hint: it's
defined on the 5.2.4.2.2 of the C standard.

V
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[Juha Nieminen]

Adem24 wrote:

"Adem24" wrote:

>// MS-Bug # 999,995 (5 left for 1 million bugs :-) :

const double d = DBL_MIN;

double v00 = 0.0;
bool f00 = v00 d;

double v01 = 0.1;
bool f01 = v01 d;

gives wrongly 'false' for f00... :-)

Further analysis shows that it has nothing todo with the DBL_MIN
but the value ZERO !
Ie. the MS compiler treats the value 0 not correctly in FP ops.

Given that DBL_MIN is a positive value (larger than 0), exactly how is
this a bug?

[=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?=]

On 2008-07-20 16:10, Adem24 wrote:

// MS-Bug # 999,995 (5 left for 1 million bugs :-) :

const double d = DBL_MIN;

double v00 = 0.0;
bool f00 = v00 d;

double v01 = 0.1;
bool f01 = v01 d;

gives wrongly 'false' for f00... :-)

Did you submit this "bug" to the gcc-team also, because I get the same
effect using gcc as with MSVC.

--
Erik Wikström

[Gennaro Prota]

Erik Wikström wrote:

On 2008-07-20 16:10, Adem24 wrote:

>// MS-Bug # 999,995 (5 left for 1 million bugs :-) :

const double d = DBL_MIN;

double v00 = 0.0;
bool f00 = v00 d;

double v01 = 0.1;
bool f01 = v01 d;

gives wrongly 'false' for f00... :-)

Did you submit this "bug" to the gcc-team also, because I get the same
effect using gcc as with MSVC.

:-) Out of curiosity, is there really a bug count for VC++, somewhere?

--
Gennaro Prota | <https://sourceforge.net/projects/breeze/>
Do you need expertise in C++? I'm available.

[Tim Roberts]

"Adem24" <ad****@adem24. org.invalidwrot e:

>"Adem24" wrote:

>>
// MS-Bug # 999,995 (5 left for 1 million bugs :-) :

const double d = DBL_MIN;

double v00 = 0.0;
bool f00 = v00 d;

double v01 = 0.1;
bool f01 = v01 d;

gives wrongly 'false' for f00... :-)

Further analysis shows that it has nothing todo with the DBL_MIN
but the value ZERO !
Ie. the MS compiler treats the value 0 not correctly in FP ops.

I can't tell from this whether you are admitting that you are wrong, or are
moving off into other foolishness. "f00" SHOULD be false. Do you now
agree with that?
--
Tim Roberts, ti**@probo.com
Providenza & Boekelheide, Inc.

[Victor Bazarov]

Gennaro Prota wrote:

[..]
:-) Out of curiosity, is there really a bug count for VC++, somewhere?

There must be. Since you can add to the collection (and check if your
addition is in the collection), there must be a way to obtain the size
of the collection, right? Now, I am not sure there is a publicly
available bug count. See https://connect.microsoft.com/VisualStudio/

V
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