On Mar 14, 2006, at 2:04 AM, Ralf W. Grosse-Kunstleve wrote:
--- Howard Hinnant <howard.hinnant@gmail.com> wrote:
According to this proposal your code would be:
std::unique_ptr<int[]> foo(unsigned size) { std::unique_ptr<int[]> result(new int[size]); // do something to result // if an exception is thrown result will be cleaned up return result; }
Hi Howard, I fetched your emulation code and tried to compile the function above; the only change I made was to put your entire file into my own namespace (instead of std::). Both EDG 245 and gcc 3.4 give similar errors:
cxx: Error: /net/legless/scratch1/rwgk/dist/iotbx/include/iotbx/pdb/ input.h, line 1035: #330-D "scitbx::unique_ptr<T [], D>::unique_ptr (scitbx::unique_ptr<T [], D> &) [with T=int, D=scitbx::default_delete<int []>]" is inaccessible return result; -----------^
Is this an oversight, or do I have to use unique_ptr<> somehow differently?
Hi Ralf, This is one of the areas where the emulated version is a little different from the real deal. You can work around this in one of two ways: unique_ptr<int[]> foo(unsigned size) { unique_ptr<int[]> result(new int[size]); // do something to result // if an exception is thrown result will be cleaned up return move(result); } or: unique_ptr<int[]> foo(unsigned size) { return unique_ptr<int[]>(new int[size]); } The move() effectively turns result into an rvalue which can then be moved from. In the move proposal the C++ language is changed such that expressions subject to RVO are implicitly treated as rvalues. Hope this helps. -Howard