https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63314
Bug ID: 63314
Summary: valarray mask/indices refers to temporary
Product: gcc
Version: 4.8.2
Status: UNCONFIRMED
Severity: blocker
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: helloworld922 at hotmail dot com
std::mask_array appears to be holding a reference to the underlying _M_data of
the mask std::valarray. This is a problem when the mask valarray is a
temporary:
std::valarray<int> data = {1,4,0,2,5};
std::mask_array<int> marr = data[data <= 2];
Here, the data <= 2 mask is a temporary and sarr will have an invalid address
for for the mask _M_data. Trying to do anything with mask_array at this point
would have problems, i.e.:
marr = 11;
will be undefined behavior.
Similarly, there is an identical issue with std::indirect_array:
std::indirect_array<int> iarr = data[std::valarray<size_t>({1,2,4})];
Because the underlying _M_data has no ownership in mask_array/indirect_array,
there are additional problems when trying to return the given type:
std::mask_array<int> doit(const std::valarray<int> &data)
{
std::valarray<size_t> idx = {1,2,3};
return data[idx];
}
It is unclear to me if this behavior is allowed by the standard, but it
certainly looks fishy, especially given that the deduced type for this:
auto marr = data[data <= 2];
is std::mask_array
