When two processes are using shared memory to communicate, and the

CreateFileMapping with PAGE_READWRITE option is used, then

are the two processes guaranteed to have serial access to the memory.

i.e. if one is writing and one is reading, does the reader get a clean
copy of the data.

Or, do you have to use mutexes to control access to the shared memory
to avoid problems?

Thanks.

Cary Lewis wrote:
You have to use mutexes or other techniques to synchronize access
yourself.

--
Scott McPhillips [VC++ MVP]

"Scott McPhillips [MVP]" <scottmcp@mvps.org> wrote in message news:<hj6dnUZh2M49SumiXTWJjw@comcast.com>...
That is what I thought, the MSDN documenation is vague on this. There
is an article that refers to "no special synronization is required,
unless there is more than one writer".

I thought that maybe because the memory mapping was abstraced through
the file system, that there was some inherent protection offered by
the operating / file system.

To be safe, and more portable the use of mutexes seems prudent.

Thank you for your quick reply.

What is your role at Microsoft?

Cary Lewis wrote:
This is a hobby. I just like answering VC questions in newsgroups :-)
MVP is an award from Microsoft to volunteers who do this a lot:

http://mvp.support.microsoft.com/

--
Scott McPhillips [VC++ MVP]