How to share HGLOBAL with another application?

Question

I\'m trying to understand something about HGLOBALs, because I just found out that what I thought is simply wrong.

In app A I GlobalAlloc() data

Answer 1

(This is just a very long comment as others have already explained that Win32 takes different approach to memory sharing.)

I would say that you are reading into books (or tutorials) on Windows programming which are quite old and obsolete as Win16 is virtually dead for quite some time.

16-bit Windows (3.x) didn't have the concept of memory isolation (or virtual /flat/ address space) that 32-bit (and later) Windows versions provide. Memory there used to be divided into local (to the process) and global sections, both living in the same global address space. Descriptors like HGLOBAL were used to allow memory blocks to be moved around in physical memory and still accessed correctly despite their new location in the address space (after proper fixation with LocalLock()/GlobalLock()). Win32 uses pointers instead since physical memory pages can be moved without affecting their location in the virtual address space. It still provides all of the Global* and Local* API functions for compatibility reasons but they should not be used anymore and usual heap management should be used instead (e.g. malloc() in C or the new operator in C++). Also several different kind of pointers existed on Win16 in order to reflect on the several different addressing modes available on x86 - near (same segment), far (segment:offset) and huge (normalised segment:offset). You can still see things like FARPTR in legacy Win16 code that got ported to Win32 but they are defined to be empty strings as in flat mode only near pointers are used.