Module abi_stable::docs::unsafe_code_guidelines

This document describes all the things that are unsafe to do with abi_stable.

De/allocation,and other global state,without going through a vtable.

It is unsafe to rely on allocators being the same across dynamic libraries, because Rust allows changing the allocator when building a dynamic library/binary.

The way this library handles allocation is by creating a vtable (virtual dispatch table) for each type that directly allocates/deallocates (ie:RVec,RBox), and storing a pointer to the vtable as a field in the type. Any method that needs it calls vtable functions to do the allocation/deallocation.

Relating to global constructors in dynamic libraries

It is unsound to do load a library developed with abi_stable or checking the layout of types with abi_stable::abi_stability::check_layout_compatibility in global constructors, because abi_stable relies on initializing its global global state in the binary and passing that global state to dynamic libraries before loading any module.

It is safe however to use anything else from abi_stable in global constructors,

“Global constructor” is any code that runs before any library symbol can be loaded, including those of abi_stable modules.