This program compiles in sequential mode but not in debug mode:
---------------------
#include <algorithm>
struct X { X(int); };
bool operator< (const X&, const X&);
void f () {
X *p, *q;
std::sort (p, q);
}
-------------------
The reason is that X does not have a default constructor. I don't think the
standard prescribes that it should need one (as a matter of fact, the
standard only talks in terms of iterators as arguments, not of the types they
point to -- if they're pointers at all). However, the parallel mode requires
a default constructor.
For reference, here's the error message:
4.3.0/parallel/multiway_mergesort.h: In function 'void
__gnu_parallel::parallel_sort_mwms(RandomAccessIterator, RandomAccessIterator,
Comparator, typename std::iterator_traits<_Iterator>::difference_type, int,
bool) [with RandomAccessIterator = X*, Comparator = std::less<X>]':
4.3.0/parallel/sort.h:88: instantiated from 'void
__gnu_parallel::parallel_sort(RandomAccessIterator, RandomAccessIterator,
Comparator, bool) [with RandomAccessIterator = X*, Comparator = std::less<X>]'
4.3.0/parallel/algo.h:1300: instantiated from 'void
std::__parallel::sort(_RAIter, _RAIter, _Compare) [with _RAIter = X*, _Compare
= std::less<X>]'
4.3.0/parallel/algo.h:1287: instantiated from 'void
std::__parallel::sort(_RAIter, _RAIter) [with _RAIter = X*]'
x.cc:7: instantiated from here
4.3.0/parallel/multiway_mergesort.h:369: error: no matching function for call
to 'X::X()'
x.cc:2: note: candidates are: X::X(int)
x.cc:2: note: X::X(const X&)
4.3.0/parallel/multiseq_selection.h: In function 'void
__gnu_parallel::multiseq_partition(RanSeqs, RanSeqs, RankType, RankIterator,
Comparator) [with RanSeqs = __gnu_cxx::__normal_iterator<std::pair<X*, X*>*,
std::__cxx1998::vector<std::pair<X*, X*>, std::allocator<std::pair<X*, X*> > >
>, RankType = int, RankIterator = __gnu_cxx::__normal_iterator<X**,
std::__cxx1998::vector<X*, std::allocator<X*> > >, Comparator = std::less<X>]':
4.3.0/parallel/multiway_mergesort.h:252: instantiated from 'void
__gnu_parallel::parallel_sort_mwms_pu(__gnu_parallel::PMWMSSorterPU<RandomAccessIterator>*,
Comparator&) [with RandomAccessIterator = X*, Comparator = std::less<X>]'
4.3.0/parallel/multiway_mergesort.h:394: instantiated from 'void
__gnu_parallel::parallel_sort_mwms(RandomAccessIterator, RandomAccessIterator,
Comparator, typename std::iterator_traits<_Iterator>::difference_type, int,
bool) [with RandomAccessIterator = X*, Comparator = std::less<X>]'
4.3.0/parallel/sort.h:88: instantiated from 'void
__gnu_parallel::parallel_sort(RandomAccessIterator, RandomAccessIterator,
Comparator, bool) [with RandomAccessIterator = X*, Comparator = std::less<X>]'
4.3.0/parallel/algo.h:1300: instantiated from 'void
std::__parallel::sort(_RAIter, _RAIter, _Compare) [with _RAIter = X*, _Compare
= std::less<X>]'
4.3.0/parallel/algo.h:1287: instantiated from 'void
std::__parallel::sort(_RAIter, _RAIter) [with _RAIter = X*]'
x.cc:7: instantiated from here
4.3.0/parallel/multiseq_selection.h:305: error: no matching function for call
to 'X::X()'
x.cc:2: note: candidates are: X::X(int)
x.cc:2: note: X::X(const X&)
4.3.0/parallel/multiseq_selection.h:305: error: no matching function for call
to 'X::X()'
x.cc:2: note: candidates are: X::X(int)
x.cc:2: note: X::X(const X&)
This sort of thing is repeated for several more pages.
W.
--
Summary: parallel v3: sort assumes that the type of the objects
to be sorted have a default constructor
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: libstdc++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: bangerth at dealii dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33489
