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https://issues.apache.org/jira/browse/STDCXX-901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12601804#action_12601804
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Martin Sebor commented on STDCXX-901:
-------------------------------------
This is from the binary incompatible rewrite of {{valarray}} that I've been
mentioning for eons (I should finally commit it on trunk). If it fixes this bug
it might spark an idea for a compatible fix...
{noformat}
// 26.3.6 - generalized slice of a valarray
class _RWSTD_EXPORT gslice
{
public:
// 26.3.6.1
gslice (): _C_imp (0) { /* no-op */ }
gslice (_RWSTD_SIZE_T,
const valarray<_RWSTD_SIZE_T>&,
const valarray<_RWSTD_SIZE_T>&);
gslice (const gslice&);
~gslice ();
gslice& operator= (const gslice&);
// 26.3.6.2
_RWSTD_SIZE_T start () const {
return _C_imp ? _C_imp->_C_start : 0;
}
valarray<_RWSTD_SIZE_T> size () const {
return _C_imp ? _C_imp->_C_length : valarray<_RWSTD_SIZE_T>();
}
valarray<_RWSTD_SIZE_T> stride () const {
return _C_imp ? _C_imp->_C_stride : valarray<_RWSTD_SIZE_T>();
}
const _RWSTD_SIZE_T _C_size () const {
return _C_imp ? _C_imp->_C_inxs.size () : 0;
}
const valarray<_RWSTD_SIZE_T>& _C_indices () const {
_RWSTD_ASSERT (0 != _C_imp);
return _C_imp->_C_inxs;
}
private:
// referenced counted gslice implementation for efficiency
struct _Imp {
_Imp (_RWSTD_SIZE_T,
const valarray<_RWSTD_SIZE_T>&,
const valarray<_RWSTD_SIZE_T>&);
valarray<_RWSTD_SIZE_T> _C_length; // set of lengths (sizes equal)
valarray<_RWSTD_SIZE_T> _C_stride; // set of strides (sizes equal)
valarray<_RWSTD_SIZE_T> _C_inxs; // cached array of indices
_RWSTD_SIZE_T _C_start; // starting offset
_RWSTD_SIZE_T _C_refs; // reference count
private:
_Imp (const _Imp&); // not copyable
void operator=(const _Imp&); // not assignable
};
_Imp *_C_imp; // reference-counted implementation or 0
};
gslice::_Imp::
_Imp (size_t beg,
const valarray<size_t>& len,
const valarray<size_t>& str)
: _C_length (len),
_C_stride (str),
_C_inxs (/* initialized below */),
_C_start (beg),
_C_refs (0)
{
_RWSTD_ASSERT (_C_length.size () == _C_stride.size ());
// compute the number of indices represented by this slice
// and store it for later so that the expensive computation
// need only be done at most once
const size_t length = _C_length.size ();
if (0 == length)
return;
size_t nelems = 1;
for (size_t i = 0; i != length; ++i) {
nelems *= _C_length [i];
}
_C_inxs.resize (nelems);
size_t small_cache [256];
const size_t cache_size = sizeof small_cache / sizeof *small_cache;
size_t* const cache =
length < cache_size ? small_cache : new size_t [length];
memset (cache, 0, length * sizeof *cache);
_C_inxs [0] = _C_start;
for (size_t i = 1; i < nelems; ++i) {
size_t inx = length;
while (inx && cache [inx - 1] == _C_length [inx - 1] - 1)
--inx;
_RWSTD_ASSERT (0 != inx);
++cache [inx - 1];
if (inx < length)
memset (cache + inx, 0, (length - inx) * sizeof *cache);
_C_inxs [i] = _C_start;
for (size_t j = 0; j != inx; ++j)
_C_inxs [i] += cache [j] * _C_stride [j];
}
if (cache != small_cache)
delete[] cache;
}
gslice::
gslice (size_t beg,
const valarray<size_t>& len,
const valarray<size_t>& str)
: _C_imp (new _Imp (beg, len, str))
{
// no-op
}
gslice::
gslice (const gslice &rhs)
: _C_imp (rhs._C_imp)
{
if (_C_imp)
_RWSTD_ATOMIC_PREINCREMENT (_C_imp->_C_refs, false);
}
gslice::
~gslice ()
{
if (_C_imp && 0 == _RWSTD_ATOMIC_PREDECREMENT (_C_imp->_C_refs, false))
delete _C_imp;
}
gslice& gslice::
operator= (const gslice &rhs)
{
if (_C_imp && 0 == _RWSTD_ATOMIC_PREDECREMENT (_C_imp->_C_refs, false))
delete _C_imp;
if (rhs._C_imp)
_RWSTD_ATOMIC_PREINCREMENT (_C_imp->_C_refs, false);
return *this;
}
{noformat}
> 26.class.gslice test fails
> --------------------------
>
> Key: STDCXX-901
> URL: https://issues.apache.org/jira/browse/STDCXX-901
> Project: C++ Standard Library
> Issue Type: Bug
> Components: Tests
> Affects Versions: 4.2.0, 4.2.1
> Environment: MSVC
> Reporter: Farid Zaripov
> Assignee: Travis Vitek
> Priority: Minor
> Fix For: 4.2.2
>
> Time Spent: 6h
> Remaining Estimate: 0h
>
> The 26.class.gslice test fails with the 162 similar assertions:
> {noformat}
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 1: expected 1, got 0
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 1: expected 1, got 0
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 1: expected 1, got 0
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 2: expected 2, got 0
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 2: expected 2, got 0
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 2: expected 2, got 0
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 3: expected 3, got 0
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 3: expected 3, got 0
> # ASSERTION (S7) (5 lines):
> # TEXT: mismatch at 0, index 3: expected 3, got 0
> ...
> {noformat}
> I'm not found the opened issue for gslice, so maybe this is another bug in
> gslice class or maybe the test itself is incorrect.
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