Question

I have a mmap typecast to a char pointer

char *ptr;

ptr = (char *)mmap(0, FILESIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

This was my earlier code. But now I want to use a map instead of char * as the requirements changed.

Now, my map is declared as
map < int, string > i_s_map;

How do I change my mmap call to point to the map?

Answer 1

You don’t want to store STL containers in shared memory, at least not share them. The reason is that they rely heavily on heap allocation, so out-of-the-box std::map will hold pointers from virtual address space of a different process.

Take a look at boost::interprocess for a way to deal with this situation in C++.