https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80064
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
Assignee|unassigned at gcc dot gnu.org |redi at gcc dot gnu.org
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I think the testcase is invalid. std::make_heap is declared like so:
template<class RandomAccessIterator>
void make_heap(RandomAccessIterator first, RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
void make_heap(RandomAccessIterator first, RandomAccessIterator last,
Compare comp);
The explicit instantiation matches the second overload, then argument
substitition creates the function:
void make_heap(vector<int>::iterator first, vector<int>::iterator last,
bool(comp)(int, int));
You can't pass functions by value so the third argument decays to:
void make_heap(vector<int>::iterator first, vector<int>::iterator last,
bool(*comp)(int, int));
However, this means the type of the function parameter comp is no longer of
type Compare, and so if the implementation tries to use that type it will fail,
e.g. GCC 7 does something like:
struct wrapper {
Compare cmp;
} wrapped_comp = { comp };
And libc++ does something like:
Compare& ref = comp;
Both fail, because Compare is a function type, but comp is a pointer to
function.
The test should use:
std::make_heap<std::vector<int>::iterator, bool(*)(int, int)>
That is the actual type that is deduced for the greater argument.
