Be careful!

I hear the old Microsoft Word save files used memory dumps, which became an undocumented nightmare of a file format.

You need total control over memory layout of the saved runtime state. No hidden fields. No pointers either - you want to be able to reload at another address. Sooner or later, you might want to add some state, and you'd need a place to put it.

That said, I have used mmap something like this, mostly so state (data) could be paged in on demand.