Superceded: RISCV Binaries as Shared Libraries

The Context

In the current development landscape, there is a growing need for more efficient and flexible ways to handle gdextension binaries. This proposal was inspired by a conversation between Fire and ホロ on June 27, 2024.

We also want to investigate players distributing riscv binaries as user generated scripts inside of godot scenes.

The Problem Statement

Traditionally we have to compile gdextension for like 5-10 platform variants which is inefficient.

Describe how your proposal will work with code, pseudo-code, mock-ups, or diagrams

Fire proposed an idea where many gdextension modules can be compiled as RISCV binaries.

Functioning like shared libraries via librisc emulation both as an intepreter or a register machine.

This could potentially allow wrapping up the entire gdextension API.

Here’s an example of how function calls into the guest VM could work:

// See further reading section.
// Host:
int ret = machine.vmcall("test", 111, 222, "333");
printf("test returned %d\n", ret);

// Guest:
extern "C" __attribute__((used, retain))
int test(int a, int b, const char* c) {
    return a + b;
}

This approach would make arbitrary function calls into the VM guest possible. The functions must be C ABI, and if you use the string name, the function must be in the symbol table.

This can also be a future approach into compiling gdscript bytecode as more performant code via string templating the bytecode as c and compiling it, but that is reserved for future work.

The Benefits

Increased efficiency and flexibility in handling RISCV binaries.
Potential to wrap the entire gdextension API.
More convenient and capable of doing things that can’t be done in gdscript.
Can also be built as a gdextension.

The Downsides

Requires significant changes to the existing system.
May introduce new complexities and potential security risks.

The Road Not Taken

Exploring other methods of improving flexibility of loading binaries - like wasm.
Holo has given me an implementation of riscv processors in godot engine via zig language.

The Infrequent Use Case

This proposal may not be beneficial for small-scale projects or those that do not require high levels of efficiency and flexibility in handling RISCV binaries.

In Core and Done by Us

This proposal will be implemented by the V-Sekai development team, with potential contributions from the wider open-source community.

Status

Status: Superseded by Build a tiny RISC virtual machine which can interpret and execute GDExtensions

Decision Makers

V-Sekai development team