CHERIoT-Platform/llvm-project

Warn if compartment call returns void

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#34 opened on Jul 3, 2024

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 (11 comments) (0 reactions) (0 assignees)LLVM (15 forks)auto 404
good first issue

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Description

It would be good if clang would warn if the return type of a compartment call is void. Compartment calls can fail unexpectedly and return -1 (e.g. due to trusted stack exhaustion). Callers should be aware of and check for this, therefore it is never appropriate for a compartment call to return void. For the same reason we should also consider automatically adding the nodiscard attribute to compartment calls.

Contributor guide

Research direction
Investigate the LLVM/clang source code to understand how compartment calls are currently handled (likely via a builtin or custom attribute). Then, in the Sema (semantic analysis) phase, add a diagnostic warning when the return type of a compartment call is void. Also consider adding 'nodiscard' attribute automatically. Look at existing warnings for similar patterns and add test cases.
Tech stack
ccpp
Domain
compilers
Issue type
Feature
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
CC++LLVM
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40