container: fix exit code return

[giuseppe]

do not return a negative value without an error.

Closes: #1977

[gemini-code-assist]

Summary of Changes

Hello @giuseppe, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the error handling within the libcrun_container_create function to provide more robust and consistent error reporting during container setup. It addresses an issue where negative values might be returned without a clear error context and improves the validation of exit codes read from a pipe. The changes ensure that container creation failures are reported consistently using the crun_make_error function, leading to clearer diagnostics and better maintainability.

Highlights

• Improved Error Handling: The logic for handling the return value of the read() system call has been enhanced to correctly identify cases where no bytes are read or an error occurs, changing the condition from ret < 0 to ret <= 0.
• Robust Exit Code Validation: Added a new check to ensure that the read() operation successfully reads the expected number of bytes (sizeof(exit_code)) and that the exit_code itself is not a negative value, preventing internal inconsistencies.
• Standardized Error Reporting: Modified the function to return a crun_make_error when container creation fails due to a non-zero exit code, aligning with the project's error reporting standards and avoiding the return of raw negative exit codes as error indicators.
• Explicit Success Return: Explicitly returns 0 when the container creation is successful (i.e., exit_code == 0), clarifying the success path.

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[gemini-code-assist]

Code Review

This pull request fixes incorrect exit code handling in libcrun_container_create. The previous implementation could return a negative value without setting an error object, or a positive value on some error paths, which is inconsistent. The changes correctly handle the exit code from the container's init process, ensuring that 0 is returned on success and a proper error is propagated on failure. The patch also improves error handling for pipe communication by checking for partial reads and EOF, making the logic more robust. Overall, this is a good fix that improves correctness and consistency.

[gemini-code-assist]

The error message is a bit generic. Including the exit_code from the container process would make it more informative for debugging purposes.

      return crun_make_error (err, 0, "error creating container: exit code %d", exit_code);

[packit-as-a-service]

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