[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116 --- Comment #8 from Jonathan Wakely --- Author: redi Date: Fri Jan 22 21:15:41 2016 New Revision: 232748 URL: https://gcc.gnu.org/viewcvs?rev=232748=gcc=rev Log: Constrain std::valarray functions and operators PR libstdc++/69116 * include/bits/valarray_before.h (__fun, __fun_with_valarray): Only define result_type for types which can be safely used with valarrays. * testsuite/26_numerics/valarray/69116.cc: New. Added: trunk/libstdc++-v3/testsuite/26_numerics/valarray/69116.cc Modified: trunk/libstdc++-v3/ChangeLog trunk/libstdc++-v3/include/bits/valarray_before.h
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116 Jonathan Wakely changed: What|Removed |Added Component|c++ |libstdc++ --- Comment #6 from Jonathan Wakely --- OK thanks for looking, I'll try constraining the valarray operator overloads.
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116
--- Comment #7 from Jonathan Wakely ---
The problem overload is this one:
template
inline _Expr<_BinClos<__shift_left, _Constant, _ValArray, _Tp, _Tp>, typename
__fun<__shift_left, _Tp>::result_type>
operator <<(const _Tp& __t, const valarray<_Tp>& __v)
{
typedef _BinClos<__shift_left, _Constant, _ValArray, _Tp, _Tp> _Closure;
typedef typename __fun<__shift_left, _Tp>::result_type _Rt;
return _Expr<_Closure, _Rt>(_Closure(__t, __v));
}
That deduces _Tp as x and so tries to instantiate valarray to see if __v can
be initialized from std::endl, which causes the "invalid abstract return type"
outside the immediate context.
It can be fixed using enable_if (or __gnu_cxx::__enable_if since this is C++98
code) to reject invalid types for valarray, maybe using __is_abstract. I just
need to figure out the best place to put it, and how many of the other
overloaded operators are affected.
It might make sense to make the first argument a non-deduced context, so we
only use this operator when the RHS is really a valarray, rather than matching
for anything on the LHS and then trying to convert the RHS to a valarray. I
don't know if that would break real code using valarray.
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116 Richard Biener changed: What|Removed |Added Priority|P3 |P2 Version|unknown |5.3.0
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116 Jonathan Wakely changed: What|Removed |Added Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |redi at gcc dot gnu.org
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116 Andrew Pinski changed: What|Removed |Added Target Milestone|--- |4.9.4
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116
--- Comment #2 from TC ---
I don't think this has anything to do with `end`. Consider the following code:
#include
template struct foo {
T f();
void g(T);
};
template void operator<<(const T&, const foo&) {}
struct x : public std::ostream
{
virtual void flush() = 0;
};
void bar(x& os)
{
os << std::endl;
}
I don't have access to 4.8.0, but this compiles on 4.7.3 and fails on 4.8.1+.
(In the case, std::operator<<(const T&, const valarray&) is
picked up by ADL.)
Deduction for this operator<< function template succeeds: `T` is deduced to be
`x` from the left operand; the right operand is a non-deduced context because
the supplied argument names a function template. Then substitution takes place,
and we instantiate valarray (whose definition is needed to decide if it can
be constructed from std::endl), which triggers a hard error because you can't
return or take an abstract type by value. This is not diagnosed in GCC 4.7.3,
likely due to PR51184.
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116
--- Comment #3 from Andrew Pinski ---
(In reply to TC from comment #2)
> Deduction for this operator<< function template succeeds: `T` is deduced to
> be `x` from the left operand; the right operand is a non-deduced context
> because the supplied argument names a function template. Then substitution
> takes place, and we instantiate valarray (whose definition is needed to
> decide if it can be constructed from std::endl), which triggers a hard error
> because you can't return or take an abstract type by value. This is not
> diagnosed in GCC 4.7.3, likely due to PR51184.
Hmm, there is a SFINAE issue here then.
We should reduce this further. A simple reduction based on the description
works still:
template struct foo {
T f();
void g(T);
};
template void operator<<(const T&, const foo&) {}
template void operator<<(const T&, void (*)(void)) {}
void endl(int);
void endl(void);
struct x
{
virtual void flush() = 0;
};
void bar(x& os)
{
os << endl;
}
--- CUT ---
Also I had confused end and endl earlier which is why I had messed up.
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116 Jonathan Wakely changed: What|Removed |Added Keywords||rejects-valid Status|UNCONFIRMED |NEW Last reconfirmed||2016-01-05 Known to work||4.7.3 Summary|compile error when |[4.9/5/6 Regression] |including valarray |compile error when ||including valarray Ever confirmed|0 |1
[Bug libstdc++/69116] [4.9/5/6 Regression] compile error when including valarray
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69116
--- Comment #1 from Andrew Pinski ---
It is trying to instantiate one of the std::end with valarray
Like:
template
inline const _Tp*
end(const valarray<_Tp>& __va)
{ return std::__addressof(__va[0]) + __va.size(); }
This does not look right.
