jsonxx | A JSON parser in C++ | JSON Processing library

Executables live in their own memory space. They do not share memory with other executables, even if they are both using the same shared library¹.

There are no interprocess mutexes in standard C++. You have to find an interprocess mutex from outside the standard.

boost has them, and most OS file system APIs can be used to create them.

Some OS APIs allow you to open files in an exclusive mode. Others rely on you created explicit locks. In some cases, this functionality may depend on the filesystem you are accessing, and even how you are accessing it.

Apparently one way to do it is to open open("unique_name.lock", O_CREAT|O_EXCL, 0777) in a specific spot you both share. Only one process can have unique_name.lock open in this way at a time.

Another is to use flock.

¹ Well, read only pages are sometimes shared by some OS's between processes; like executable code. And even read-write pages can be copy-on-write shared. This kind of sharing, however, happens just "as if" it didn't happen. Also, address space layout randomization makes this optimization less useful.