Do I need to delete an static std::map?

In some classes I have an static std::m开发者_开发技巧ap with pointers inside. My question is if I need to delete at the end of the program or this memory is automatically freed. My concern is if the pointers stored inside are correctly deleted through our destructors when std::map is deleted.

Thanks.

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If the map contains pointers that were allocated with new (or new[], or malloc), then each pointer needs a corresponding delete (or delete[], or free).

The map's destructor wont know what to do with a bald pointer. Consider using a smart pointer that has appropriate move semantics like a boost smart pointer or if you've got a very new compiler, one of the C++0x smart pointers. However, do not use the current standard's std::auto_ptr, inside of STL containers. See this thread for why.

Edit:

As Billy ONeal pointed out, boost::ptr_map is also designed exactly for this purpose.

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If I understand the situation correctly, you don't delete the map itself. But you probably need to delete the objects the map is pointing to. It would probably be a really good idea to use a smart pointer such as Boost shared_ptr in your map instead of native pointers. Then the objects would be cleaned up automatically.

Edit: Using Boost ptr_map might be an even better idea.

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The memory is "automatically freed", in the sense that the entire process memory is freed, but the destructors of the objects pointed to will not be called. This can cause a resource leak, if you use RAII.

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std::map never calls delete on it's members. Assuming you're working with a relatively recent operating system, the OS will reclaim the memory occupied by the members on process termination, but the destructors will not run.

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If you have a map of pointers, then the answer is 'no', your destructors will not be called, but 'yes', the memory will be freed at the end of process execution. All memory allocated by a process is always freed by the Operating System when a process exits (even if it crashes), but destructors might not be called.

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A memory "leak" is where memory is unintentionally not deleted over a period of time, and ends up reducing as the process continues. If it is a type of process that runs for a very long period of time, eg a server that is rarely restarted, this can be a major problem.

Memory leak detectors will pick up on any memory that is allocated and not deleted by a programming call, so valgrind, etc. will report this as a leak.

It is as well to check your code with programs like valgrind, and therefore the less that "gets in the way", the easier it will be to spot real leaks. Therefore my advice is not do just let the system clean up the memory, or singletons, etc, for you when you have allocated a pointer with new (or malloc or new[]).

You can have a "clean-up" routine to do this. Just have an object in the scope of your map that has a deleter (as it will be deleted when it exits) that will clean up the pointers in the map. As you need your object to be deleted first it should be declared later than the map.

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Like in any case of storage class which stores pointers: you are responsible to deallocate memory they point to. Storage class is responsible only to clean its own resources. Relying on reclaiming memory by OS at the process termination is a bad practice.