[PATCH][libstdc++-v3 parallel mode] Avoid taking address of dereferenced random access iterator
Jonathan Wakely
jwakely.gcc@gmail.com
Thu Mar 10 10:37:00 GMT 2011
On 10 March 2011 09:47, Johannes Singler wrote:
> The attached patch patch solves a conformance problem of the parallel mode
> helper routine multiseq_partition. I have added a test case for that.
> multiseq_selection has similar problems, but is unused, so I plan to remove
> that completely (which might ask for renaming of the file and the test).
Please update the copyright date in the changed file as well.
> Should I use unique_ptr (or alloca, or something similar) here for a better
> exception safety (this routine is not parallel itself)?
unique_ptr is C++0x only, auto_ptr would work. But I see other heap
allocation in that function are already unguarded so there doesn't
seem to be much point guarding one and not the others. How about
defining a local RAII type (and combining the three allocations into
one) e.g.
struct _Guard
{
_DifferenceType* _M_ns;
~_Guard() { delete[] _M_ns; }
} __guard = { };
__guard._M_ns = new _DifferenceType[__m*3];
_DifferenceType* __ns = __guard._M_ns;
_DifferenceType* __a = __guard._M_ns + __m;
_DifferenceType* __b = __guard._M_ns + 2*__m;
_DifferenceType __l;
That ensures the _Guard destructor will clean up on exiting the
function, so you can remove the delete statements.
and
std::auto_ptr<_ValueType> __lmax;
...
__lmax.reset(new _ValueType(__S(__i)[__a[__i] - 1]));
etc.
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