Inside STL: Smart Pointers -- Raymond Chen

By Blog Staff | Oct 3, 2023 09:47 AM | Tags: None

The C++ standard library comes with a few smart pointer types. The simplest one is unique_ptr: This class babysits a raw pointer and remembers to delete it at destruction (in an appropriate manner). Dumping the contents of a unique_ptr is just looking at the raw pointer inside.

Inside STL: Smart Pointers

By Raymond Chen

From the article:

The C++ standard library comes with a few smart pointer types.

The simplest one is unique_ptr: This class babysits a raw pointer and remembers to delete it at destruction (in an appropriate manner). Dumping the contents of a unique_ptr is just looking at the raw pointer inside.

The complication is that there is also a deleter object in the unique_ptr. This deleter object is usually an empty class, so it is stored as part of a compressed pair.

The Visual Studio debugger has a visualizer that understands unique_ptr, but here’s what it looks like at a low level in the Microsoft implementation:

0:000< ?? p
class std::unique_ptr<S,std::default_delete<S> >
   +0x000 _Mypair          : std::_Compressed_pair<std::default_delete<S>,S *,1>
0:000< ?? p._Mypair
class std::_Compressed_pair<std::default_delete<S>,S *,1>
   +0x000 _Myval2          : 0x0000020a`11f08490 S
0:000< ?? p._Mypair._Myval2
struct S * 0x0000020a`11f08490 ← here is the unique object
   +0x000 a                : 0n42