Document error handling

[eriksjolund]

WIP (work-in-progress)

Note, not all crun source code follows the suggested error handling convention
For example

• https://github.com/containers/crun/blob/22489efa2f5278d34bf781f998288fd9689d07ec/src/libcrun/container.c#L1562C1-L1571C18

where a negative value is returned but there is no allocated libcrun_error_s (in line 1571).

Closes: #1860

Summary by Sourcery

Documentation:

• Add a design document describing standard error handling patterns and expectations for libcrun_error_t-based APIs, including success/failure semantics and known exceptions.

[sourcery-ai]

Reviewer's Guide

Adds a new design document describing the standard error-handling conventions for C source files under src/, including expected function signatures, success/failure return patterns, and libcrun_error_s usage, with a placeholder section for documented exceptions.

File-Level Changes

Change	Details	Files
Introduce design documentation for C error-handling conventions using libcrun_error_t and libcrun_error_s.	Create a new error_handling.md design document under design-docs/ Specify the required function signature pattern using libcrun_error_t *err and int/pointer returns for functions that can fail Define success semantics: return 0 or non-NULL pointer and leave the err argument untouched Define failure semantics: return negative value or non-NULL pointer and set err to an allocated libcrun_error_s with errno-style status and allocated message Clarify that err must not point to an already allocated libcrun_error_s Add a placeholder section to later enumerate exceptions to these conventions	design-docs/error_handling.md

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#1860	Document the error handling convention used in the crun C source code (for functions taking libcrun_error_t *err), including how return values relate to error creation and the expectation that callers do not pass an already-created error object.	✅

Possibly linked issues

• Document error handling convention #1860: PR introduces error_handling.md documenting the libcrun_error_t error convention exactly as requested in the issue.
• Document error handling convention #1860: They both concern how negative return values and libcrun_error_s are handled; PR documents this exact error convention.

---

Tips and commands

Interacting with Sourcery

• Trigger a new review: Comment @sourcery-ai review on the pull request.
• Continue discussions: Reply directly to Sourcery's review comments.
• Generate a GitHub issue from a review comment: Ask Sourcery to create an
  issue from a review comment by replying to it. You can also reply to a
  review comment with @sourcery-ai issue to create an issue from it.
• Generate a pull request title: Write @sourcery-ai anywhere in the pull
  request title to generate a title at any time. You can also comment
  @sourcery-ai title on the pull request to (re-)generate the title at any time.
• Generate a pull request summary: Write @sourcery-ai summary anywhere in
  the pull request body to generate a PR summary at any time exactly where you
  want it. You can also comment @sourcery-ai summary on the pull request to
  (re-)generate the summary at any time.
• Generate reviewer's guide: Comment @sourcery-ai guide on the pull
  request to (re-)generate the reviewer's guide at any time.
• Resolve all Sourcery comments: Comment @sourcery-ai resolve on the
  pull request to resolve all Sourcery comments. Useful if you've already
  addressed all the comments and don't want to see them anymore.
• Dismiss all Sourcery reviews: Comment @sourcery-ai dismiss on the pull
  request to dismiss all existing Sourcery reviews. Especially useful if you
  want to start fresh with a new review - don't forget to comment
  @sourcery-ai review to trigger a new review!

Customizing Your Experience

Access your dashboard to:

• Enable or disable review features such as the Sourcery-generated pull request
  summary, the reviewer's guide, and others.
• Change the review language.
• Add, remove or edit custom review instructions.
• Adjust other review settings.

Getting Help

• Contact our support team for questions or feedback.
• Visit our documentation for detailed guides and information.
• Keep in touch with the Sourcery team by following us on X/Twitter, LinkedIn or GitHub.

[giuseppe]

Thanks for tackling this one!

Do you think we could also add an AGENTS.md file that links to this file?

[packit-as-a-service]

TMT tests failed. @containers/packit-build please check.