[rwmcguir]

Summary

Fix the stdout-capture helper used by tests_multi_driver_stdout and tests_sigle_driver_stdout.

Windows container CI confirmed tmpnam_s returned 34 (ERANGE) with the existing 50-byte filename buffer. Its temporary directory was C:\Users\ContainerAdministrator\AppData\Local\Temp, leaving insufficient room for the generated filename. Previously unchecked errors led to invalid descriptor operations and Windows fail-fast termination (0xc0000409).

Changes

• Use L_tmpnam_s for the Windows filename buffer; retain the Linux mkstemp template with a compile-time size.
• Check filename generation, file opening, descriptor duplication/redirection/restoration, and capture-file access/cleanup.
• Stop the test if capture setup fails rather than passing invalid descriptors onward.
• Remove investigative stderr diagnostics. Success is silent; actual failures are reported through GoogleTest with relevant error codes.

Validation

• Diagnostic Windows container CI established the failing operation and ERANGE result.
• Compiled the exact updated helper with C++14, warnings-as-errors, AddressSanitizer, and UndefinedBehaviorSanitizer on Linux.
• Verified quiet successful capture/restoration and explicit invalid-descriptor failures.
• Tested the Windows branch with mocked CRT calls, including filename-generation and file-open failures.
• Long-temp-path regression: old 50-byte buffer fails, L_tmpnam_s buffer passes; temporary files are cleaned up.
• Actual Windows execution of the final fix remains pending. Consumer CI already selects this PR head; rerunning those jobs will test the updated fix.

[github-actions]

Level Zero loader ABI check

last-release (v1.35.0): ✅ no ABI problems. Report

Creating compatibility report ...
Binary compatibility: 100%
Source compatibility: 100%
Total binary compatibility problems: 0, warnings: 0
Total source compatibility problems: 0, warnings: 0

master (master): ✅ no ABI problems. Report

Creating compatibility report ...
Binary compatibility: 100%
Source compatibility: 100%
Total binary compatibility problems: 0, warnings: 0
Total source compatibility problems: 0, warnings: 0

Workflow run

If an ABI change is intended, a reviewer with write access can accept it: leave an approval review on the PR head commit with the keyword abi-failure-approved in the review body. That re-runs the check.