> 1. This will actually simplify the code for calculating the stack size.

Simplify whose code, the caller or the callee?  It seems like it's simplifying the life of the callee (PyCompile_OpcodeStackEffectEx) at the expense of pushing complexity into the caller.


> 2. This will simplify third-party compilers (like
> https://github.com/vstinner/bytecode). They wouldn't need to
> duplicate the complicated code.

What complicated code?  Compilers simply call PyCompile_OpcodeStackEffect(), passing in an opcode + oparg pair, and it simply returns the maximum stack effect.  No crazy "is it a jump" logic needed.  Again: this may mean overallocating the stack.  But CPython has behaved like this for twenty years and I'm not convinced it's a problem that needs solving.


Victor, do you want to use Serhiy's proposed API in your library?