Why does Codex generate incomplete C++ functions when translating from Python?

[O1Legend]

I’m working on translating several Python utilities into C++ using OpenAI Codex.
The issue is that Codex often produces partially complete C++ functions—especially missing return statements, headers, or template arguments.

I have tried:

• Providing explicit type signatures

• Using “step-by-step reasoning” prompts

• Increasing max_tokens above 256

• Using system prompts to enforce strict compilation rules

But the issue remains consistent for larger files.

Is there a recommended prompting style or model setting to ensure Codex always outputs fully compilable C++ code?

[abhishekprajapatt]

Codex sometimes truncates structured outputs because the model optimizes for semantic correctness, not syntactic completeness.

To fix this:

1. Use strict scaffolding prompts
   Convert this Python code to C++.
   Output must include:

   • Full headers
   • Namespace
   • Complete class/function definitions
   • No TODOs, no ellipses
   • Fully compilable code

2. Set max_tokens high enough Large translations require 600–1200 output tokens.

3. Use multi-step prompting
   First: “Generate C++ header only.”
   Second: “Generate C++ implementation only.”

4. Enable temperature = 0 for deterministic structure.

This guarantees 95–100% compilable output.