[cfe-dev] Small C++ query

Keno Fischer kfischer at college.harvard.edu
Mon May 25 20:03:38 PDT 2015

Hi folks,

I'm confused by the following code snippet:

#include <memory>
void foo(int *x) { std::unique_ptr<int>(x); }

both clang and gcc warn that this redefines x, but I don't understand why
is a declaration of x. I guess I would have expected a temporary unique_ptr
that gets destructed immediately or an error. How come this actually
defines a variable called x?

To give some background about where this came up, a user wanted to do
C++> std::unique_ptr<int>(x);
in my Clang-based interactive C++ REPL. Behind the scenes this gets
transformed into the function above and then I try to insert a return
statement on the last statement in the body to automatically grab the
result. This works well in most cases but failed here because Clang thinks
this is a variable declaration, so I'd like to understand why this is

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