[Bug libstdc++/42242] vector::resize unnecessarily calls null constructor

[redi at gcc dot gnu dot org]

--- Comment #1 from redi at gcc dot gnu dot org  2009-12-01 18:21 ---
this is caused by the default argument to resize:

void
resize(size_type __new_size, value_type __x = value_type());


It would be possible to avoid the default construction by replacing that member
with two overloads of resize, but I'm not sure it's worth doing.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42242

[Bug libstdc++/42242] vector::resize unnecessarily calls null constructor

[redi at gcc dot gnu dot org]

--- Comment #2 from redi at gcc dot gnu dot org  2009-12-01 18:30 ---
On second thoughts, it might be necessary to split it into two overloads for
C++1x, because this should work:

#include vector

struct moveable {
explicit moveable(int) { }
moveable(const moveable) = delete;
moveable(moveable) { }
};

int main()
{
std::vectormoveable v;
moveable m(0);
v.resize(1, m);
}


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42242

[Bug libstdc++/42242] vector::resize unnecessarily calls null constructor

[pinskia at gcc dot gnu dot org]

--- Comment #3 from pinskia at gcc dot gnu dot org  2009-12-01 18:33 ---
(In reply to comment #1) 
 It would be possible to avoid the default construction by replacing that 
 member
 with two overloads of resize, but I'm not sure it's worth doing.

The C++03 standard only lists the function with the default value so this is
invalid.


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pinskia at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution||INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42242

[Bug libstdc++/42242] vector::resize unnecessarily calls null constructor

[pinskia at gcc dot gnu dot org]

--- Comment #4 from pinskia at gcc dot gnu dot org  2009-12-01 18:34 ---
(In reply to comment #2)
 On second thoughts, it might be necessary to split it into two overloads for
 C++1x, because this should work:

But std::vector::resize (size_type sz, T c = T()); is the only one listed at
least in C++03.  What does C++1x say about that function?  You might need to
raise this to the C++ standards committee.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42242

[Bug libstdc++/42242] vector::resize unnecessarily calls null constructor

[redi at gcc dot gnu dot org]

--- Comment #5 from redi at gcc dot gnu dot org  2009-12-01 18:37 ---
(In reply to comment #2)
 On second thoughts, it might be necessary to split it into two overloads for
 C++1x, because this should work:

Gah, ignore that, I'm talking rubbish and that shouldn't work

Andrew, the standard would allow two overloads instead of one, see
[member.functions]/2 - and the C++1x draft specifies two separate overloads. 
It's a reasonable enhancement request IMHO, but necessarily not a bug.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42242