On Nov 16, 2012, at 7:00 AM, Maxim Yanchenko <MaximYanchenko@yandex.ru> wrote:
Olaf van der Spek <ml <at> vdspek.org> writes:
On Fri, Nov 16, 2012 at 3:25 PM, Mathias Gaunard <mathias.gaunard <at> ens-lyon.org> wrote:
void f(std::string const&); f("Olaf");
Are compilers/optimizers not smart enough to construct the temporary object at compile time?
I'm afraid they are not smart enough to eliminate an unneeded temporary when it's something sophisticated like std::string…
Actually, this is a really good example. void f(std::string const&); void g(string_ref); f("Olaf"); g("Olaf"); In the call to "f", the compiler will create a temporary std::string. This will involve a call to strlen (possibly done at compile time), a memory allocation (modulo the small-string optimization), and copying the data. In the call to "g", the compiler will create a temporary string_ref. This will involve a call to strlen (possibly done at compile time). And for most cases, the code internal to "f" and "g" won't care that they got a string_ref instead of a const std::string. -- Marshall Marshall Clow Idio Software <mailto:mclow.lists@gmail.com> A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait). -- Yu Suzuki