>I want to use memory mapped files to store my application specific
>data. I will be needing lists and maybe some other STL classes. Since
>memory mapped files are no more than a range of ordinary addresses in
>user space, I thought I might use STL lists instead of inventing my
>own but one big problem arises. Memory mapped file can be mapped to
>different start address each time it's created so list's pointers
>should actually be offsets to the beginning of the file and not actual
>pointers. Offsets are easily translated into actual pointers by adding
>the start address of a memory mapped file.

>Has anybody ever done anything like this? I am not an expert in STL so
>I'm seeking help. I thought that changing std::allocator class will do
>the trick. I have looked at the source of std::allocator and std::list
>and haven't found a way to do what I want. Am I just missing something
>or is it really impossible?

>std::list, std::map, etc. use pointers internally. Unless you can guarantee
>the shared memory is mapped to the same logical address in all apps using a
>shared STL container, it won't work. If you can guarantee this, don't forget
>that the list, map, or whatever must itself reside in the shared memory, and
>any memory dynamically allocated by the container's values must reside in
>the shared memory as well. For example, suppose you arrange for a std::list
>object to reside in a shared memory section named X, and you give it an
>allocator that allocates from X. If the list contains strings, the strings
>must also obtain their dynamic storage from X; the list's allocator
>parameter is concerned only with allocations made by the list, not
>allocations made by objects stored in the list.