Re: How do I ensure only one version of my executable is running
"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:7r13v2h4js78kbk04v6gkji00tkcos6tm9@4ax.com...
Some problems here...
The MAX_PATH value for the command line is far too small. Imagine six
filenames with long
paths on the command line.
Sure, storing the command-line has always been an issue, especially with UNC
filenames. In practice though, setting the buffer to something reasonable
like 4KB makes it deployable. Also using StringCbCopy to protect from
overrun.
There must be a lock protecting this variable, which is set by
the sender and released by the receiver, and a mutex or CRITICAL_SECTION
will not work
for this; it must be a binary semaphore. It is usually better to use
something llike
WM_COPYDATA to send the command line information across.
No, the variable is SHARED, there is no "sending across" any information.
When the app starts up, it checks if the command-line has been init by
another instance, and if so, it just reads it.
There is no more synchronization problem here than your usage of creating a
mutex. Both have the issue where it is possible for 2 instances to be
simultaneously started, check for the mutex, see it's not there, and create
it at the same time. This case is rightfully ignored because of the vitual
impossibility of starting 2 instances of an .exe that close together.
-- David