How to share data between different instance of same DLL

Usually Dlls are loaded into its corresponding process address space. Indeed the code is shared between all instances but not the global data. So the issue that we might face is – how can we share common data between all dll instances?

#pragma data_seg (".MYSEG")
    int g_nInteger = 0;
    char g_szString[] = "hello world";
#pragma data_seg()

// Tell the linker that the section
// .MYSEG is readable, writable and is shared.
#pragma comment(linker, "/SECTION:.MYSEG,RWS")

Here we are declaring our data segment and are telling that, this segment is RWS – readable, writable and shared. This way we manage to share this data segment between all dll instances.

Comments

[binaries]

The simplest example is to use it for inter-process data communication. If it creates a dll with the above shared section and load this dll file in multiple processes, the dll will be loaded into the virtual memory space of each different process, but the shared section will allow all processes to access the data equally.

[Pierre Gradot]

Can present a typical use-case where this is useful? :)