Re: Making use of move semantics?

[Daniel Boles <dboles src gmail com>]

On 22 May 2017 at 11:23, Jonathan Wakely <gtkmm kayari org> wrote:

On 21 May 2017 at 10:36, Daniel Boles wrote:

I still occasionally find myself reflexively std::move()ing strings into glibmm/gtkmm functions that I unconsciously see as taking ownership of their arguments - only to realise it makes no difference because all of them take strings as const&.

This made me wonder whether there are any cases where, if the user instructs so by using std::move(), glibmm/gtkmm functions could steal the string [ or at least it's c_str() ] and thus avoid having to copy it. All those copies quickly add up to a lot.

 

You can't steal the contents of a std::string without access to its internals, which only the standard library has. You can't steal the c_str() ... I'm not even sure what that would mean.

 

Saying "steal" was partly just my hamfisted way of explaining what the move constructor of an std::string (or Glib::ustring) would do. But yeah, partly I was half asleep, and imagining that maybe a C API could grab the char* from a std::string or whatever and leave it in a 'moved-from' kinda condition. Which is nonsense like you said, since there's no API for anything like that.