Windows CreateFileMapping : different file-mapping objects with same backed file

Question

I know that we can use file mapping to share contents between two processes, but this requires the same file mapping object.

what will happen if each process creates its own file mapping object with its own file handle,but each file handle points to the same file?

thanks Chang

Answer 1

From documentation:

Creating a file mapping object does not actually map the view into a process address space. The MapViewOfFile and MapViewOfFileEx functions map a view of a file into a process address space.

With one important exception, file views derived from any file mapping object that is backed by the same file are coherent or identical at a specific time. Coherency is guaranteed for views within a process and for views that are mapped by different processes.

The exception is related to remote files. Although CreateFileMapping works with remote files, it does not keep them coherent. For example, if two computers both map a file as writable, and both change the same page, each computer only sees its own writes to the page. When the data gets updated on the disk, it is not merged.