Re: [PATCH v6] C++ify gdb/common/environ.c

[Simon Marchi <simon dot marchi at polymtl dot ca>]

On 2017-06-19 17:44, Pedro Alves wrote:
> If we take the "always push a NULL on construction" approach, and
> we want moved-from gdb_environs to be valid, then yes.  Note how this
> results in extra heap allocations when e.g., returning a
> gdb_environ from functions by value, and makes std::vector<gdb_environ>
> much less efficient when it decides it needs to reallocate/move
> elements.  Representing the empty state with a cleared internal
> vector would avoid this.

Given the move case, since the goal is to be efficient, then yeah I 
would agree
that it would make sense to make a little bit of efforts to avoid 
allocating
memory for an objects we are almost certainly throwing away.

But still, in order to leave environ objects in a valid state after a 
move and
to pedantically comply with the STL spec which says that the vector is 
left in
an unspecified state, shouldn't we do a .clear () on the moved-from 
vector after
the move?

> Note BTW, that we need to be careful with self-move leaving the
> *this object in a valid state.

Should we just do

if (&other == this)
  return *this;

?