Migrating from std::auto_ptr to std::unique_ptr (Supporting Multiple Compilers)
In this blog post, we will explore various techniques to migrate your code from std::auto_ptr to std::unique_ptr, ensuring compatibility with both modern and older C++ compilers.
1. Utilizing boost::unique_ptr:
For compilers that do not support std::unique_ptr, you can use boost::unique_ptr as a suitable alternative. boost::unique_ptr offers a similar interface and semantics to std::unique_ptr, making it a straightforward replacement.
#include
boost::unique_ptr ptr(new int(10));
int value = *ptr; // Dereference the unique pointer
2. Conditional Compilation:
Conditional compilation allows you to selectively use std::auto_ptr or std::unique_ptr based on the C++ standard version. This technique involves defining preprocessor macros to differentiate between compiler versions and then conditionally including the appropriate header files or code blocks.
#if __cplusplus < 201103L
#include // For std::auto_ptr
#else
#include // For std::unique_ptr
#endif
#if __cplusplus < 201103L
std::auto_ptr ptr(new int(10));
#else
std::unique_ptr ptr(new int(10));
#endif
3. Namespace Aliasing and Using Declarations:
You can also employ namespace aliasing and using declarations to provide a unified interface across different compiler versions. This involves creating aliases or using declarations that effectively map std::auto_ptr to std::unique_ptr for compilers that support the latter.
#if __cplusplus < 201103L
using auto_ptr = std::auto_ptr;
#else
using auto_ptr = std::unique_ptr;
#endif
auto_ptr ptr(new int(10)); // Uses auto_ptr, which is aliased to the appropriate type
4. Wrapping with a Custom Smart Pointer Class:
Another approach is to create a custom smart pointer class that encapsulates either std::auto_ptr or std::unique_ptr, depending on the C++ standard version. This provides a consistent interface for your code while internally handling the necessary adaptations.
template
class SmartPtr {
#if __cplusplus < 201103L
std::auto_ptr ptr;
#else
std::unique_ptr ptr;
#endif
public:
SmartPtr(T* ptr) : ptr(ptr) {}
T* get() { return ptr.get(); }
};
SmartPtr ptr(new int(10)); // Uses SmartPtr, which internally handles the correct smart pointer type
Conclusion:
Migrating from std::auto_ptr to std::unique_ptr while supporting multiple compilers requires careful consideration and the selection of an appropriate strategy. Techniques like utilizing boost::unique_ptr, conditional compilation, namespace aliasing, and custom smart pointer classes can help achieve this goal effectively.