Consider a smaller stack size

[SuperFola]

The problem

Creating a VM requires creating an ExecutionContext, that holds a few important values, such as the stack for the VM, defined as a std::array<Value, VmStackSize>. As of today, sizeof(Value) returns 40B, and the stack size is set to 8192 ; creating a VM thus requires 327kB.

Some tidbits about the compiler

The compiler can handle stack cleaning (ie a (while true 1) won't trash the stack luckily), and also handles correctly self tail calls (something is in the works to handle generic tail calls).

Generic tail calls will require a new instruction, akin to JUMP but for pages, so that we can jump between functions. Development on this should start shortly after having integrated the new parser.

Questions and experiments

• do we still need a stack THIS big?
• how does it currently affects script startup?
  • similarly, how does this affects the use of (async foo arg...)?

Data will be needed on the optimal stack size and the average stack size for common scripts.

Final words

Even though this would change a critical part of the virtual machine, this can not be considered a breaking change as the stack is never exposed to the end user (nor to plugin authors).

[SuperFola]

Thinking back about it, that would break recursion-intensive scripts that currently work.

A single function call takes at least 2 slots on the stack, for the old IP and PP to jump back to (which are not needed in tail calls luckily).

Might have to experiment with a stack size of 4096, maybe 2048, but I wouldn't go lower.