Module allocator

In this module is a shared memory allocator that can be used in Shadow to share data between the main simulator process and managed processes. There are three main global functions that are provided:

(1) shmalloc(), which places the input argument into shared memory and returns a Block smart pointer. (2) shfree(), which is used to deallocate allocated blocks. (3) shdeserialize(), which is used to take a serialized block and convert it back into a Block smart pointer that can be dereferenced.

Blocks can be serialized with the .serialize() member function, which converts the block to a process-memory-layout agnostic representation of the block. The serialized block can be one-to-one converted to and from a string for passing in between different processes.

The intended workflow is:

(a) The main Shadow simulator process allocates a shared memory block containing an object. (b) The block is serialized. (c) The serialized block is turned into a string. (d) The string is passed to one of Shadow’s child, managed processes. (e) The managed process converts the string back to a serialized block. (f) The serialized block is deserialized into a shared memory block alias. (g) The alias is dereferenced and the shared object is retrieved.

Structs

ShMemBlock

A smart pointer class that holds a Sync and VirtualAddressSpaceIndependent object.

ShMemBlockAlias

This struct is analogous to the ShMemBlock smart pointer, except it does not assume ownership of the underlying memory and thus does not free the memory when dropped.

ShMemBlockSerialized

SharedMemAllocator

Safe wrapper around our low-level, unsafe, nostd shared memory allocator.

SharedMemAllocatorDropGuard

The intended singleton destructor for the global singleton shared memory allocator.

SharedMemDeserializer

Functions

shdeserialize^⚠

This function takes a serialized block and converts it back into a BlockAlias that can be dereferenced.

shfree

This function frees a previously allocated block.

shmalloc

This function moves the input parameter into a newly-allocated shared memory block. Analogous to malloc().