[STDCXX-224] std::valarray::operator[](slice) broken

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Cannot Reproduce
• Fix Version/s: 4.2.0
• Component/s: 26. Numerics

Environment

all

• Severity: Incorrect Behavior
• Assignee: Martin Sebor
• Reporter: Martin Sebor
• Created: 29/Jun/06 01:21
• Updated: 14/Oct/07 23:11
• Resolved: 14/Oct/07 23:11

Description

Moved from the Rogue Wave bug tracking database:

***Created By: sebor @ Mar 16, 2003 06:51:05 PM***
Subject: CXX-DEV: Bug in valarray / slice_array?
[e-mail]
Date: 03/13/03

next message: Martin Sebor: "Re: CXX-DEV: Bug in valarray / slice_array?"
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reply: Martin Sebor: "Re: CXX-DEV: Bug in valarray / slice_array?"

Hello,

The following program results in incorrect results:

#include <valarray>
#include <iostream>
int main() {

int vals[] =

{1,0}

;
const std::valarray<int> p( vals, 2 );

for ( int i =0; i<p.size(); i++ )
std::cout << "p:" << i << "=" << p[i] << std::endl;

const std::valarray<int> r = p[ std::slice( 0, 0, 1 ) ];
for ( int i =0; i<r.size(); i++ )
std::cout << "r:" << i << "=" << r[i] << std::endl;

return 0;
}

Output:
LT:tmp 223 0>aCC -AA -g1 -o val.hp val2.C
LT:tmp 224 0>./val.hp
p:0=1
p:1=0
r:0=0
r:1=0

A slice is specified with size 0. Therefore I expect that valarray 'r' is
of size 0 and no output should
appear for 'r'.
Note that I make use of const valarrays. In that case a valarray is
returned by valarray::operator[].

The problem disappears when I remove the 'const's. In that case a
slice_array is
returned by valarray::operator[] and used to construct valarray 'r'. The
output when 'const' is removed is:
LT:tmp 226 0>./val.hp
p:0=1
p:1=0

Compiler: aCC: HP ANSI C++ B3910B A.03.37

Do I something wrong or is this a compiler / library bug?

Thanks.
Regards, Mario.

[e-mail]
Philips Research Laboratories; Electronic Design & Tools;
Building WAY3.27, Prof. Holstlaan 4 Phone: [phone]
5656 AA Eindhoven, The Netherlands Fax: [phone]
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***Modified By: sebor @ Mar 16, 2003 06:59:07 PM***
-------- Original Message --------
Subject: [Fwd: Re: CXX-DEV: Bug in valarray / slice_array?]
Date: Sun, 16 Mar 2003 18:49:46 -0700
From: Martin Sebor <[e-mail]>
Organization: Rogue Wave Software, Inc.
To: Dennis Handly <[e-mail]>

Dennis,

Here's a fix for the bug if you want to incorporate it. From
briefly looking at <valarray> I suspect that there are a ton
of subtle and not so subtle bugs such as this one and even
more efficiency improvements that could be made; a complete
rewrite will probably be necessary to make the class(es)
useful.

Martin

template <class _TypeT>
inline valarray<_TypeT>
valarray<_TypeT>::operator[] (slice __sl) const
{
if (0 == __sl.size ())
return valarray<_TypeT>();

RWSTD_ASSERT (_sl.start () < size ());
_RWSTD_ASSERT (0 != __sl.stride ());

const _RWSTD_SIZE_T __size =
size () < __sl.start () + __sl.size () * __sl.stride () ?
(size () - __sl.start ()) / __sl.stride () : __sl.size ();

RWSTD_ASSERT (_size <= size ());

RW::_rw_array <_TypeT> __tmp =
RW::_rw_array <_TypeT>(_TypeT (), __size);

for (_RWSTD_SIZE_T __i = __sl.start (), __j = 0; __j != __size;
_i += __sl.stride (), ++_j)
__tmp [__j] = _C_array [__i];

return valarray<TypeT>(_tmp);
}

-------- Original Message --------
Subject: Re: CXX-DEV: Bug in valarray / slice_array?
Date: Fri, 14 Mar 2003 11:53:24 -0700
From: Martin Sebor <[e-mail]>
Reply-To: [e-mail]
Organization: Rogue Wave Software, Inc.
To: [e-mail]
References:
<[e-mail]>

[e-mail] wrote:
> Hello,
>
> The following program results in incorrect results:
>
...
>
> A slice is specified with size 0. Therefore I expect that valarray
'r' is
> of size 0 and no output should
> appear for 'r'.
> Note that I make use of const valarrays. In that case a valarray is
> returned by valarray::operator[].
>
> The problem disappears when I remove the 'const's. In that case a
> slice_array is
> returned by valarray::operator[] and used to construct valarray 'r'. The
> output when 'const' is removed is:
> LT:tmp 226 0>./val.hp
> p:0=1
> p:1=0
>
> Compiler: aCC: HP ANSI C++ B3910B A.03.37
>
>
> Do I something wrong or is this a compiler / library bug?

It's a bug in valarray::operator[](slice) const.

Regards
Martin