canonical/mir

Move from `snprintf` and friends to `std::format*` and add checks for truncation

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#4,549 opened on Dec 15, 2025

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Good first issue

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Description

We should print if the output message was truncated to avoid red-herrings while debugging. In addition, it might be a good idea to move from the old printf style prints to std::format. Where allocation is not possible (error handling), std::format_to can also be used.

This covers printf, snprintf, vnprintf and other variants.

Contributor guide

Research direction
Search for all uses of snprintf, vnprintf, and related functions in the codebase. Identify where truncation could occur and add checks. Use std::format for new code and std::format to for allocation free contexts.
Tech stack
cpp
Domain
backend
Issue type
Refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65