[JinmingHu (Jinming-Hu)]

Summary

Add -fprofile-update=atomic to the existing GNU Debug coverage compiler flags in cmake-modules/AzureCodeCoverage.cmake. This makes coverage-counter updates thread-safe when instrumented SDK code is called concurrently.

This is a candidate fix for intermittent gcovr NegativeHits failures, not a claim that their exact cause has already been established. GCC documents atomic updates as preventing profile corruption in multithreaded applications: https://gcc.gnu.org/onlinedocs/gcc-13.4.0/gcc/Instrumentation-Options.html#index-fprofile-update

Evidence

The same Ubuntu Storage LIVE coverage job failed while processing storage_bearer_token_authentication_policy.cpp.gcda on main and on #7448:

• Main build 6945688: https://dev.azure.com/azure-sdk/internal/_build/results?buildId=6945688&view=logs&logId=3300
• Add STG105 Storage features #7448 build 6955780, retry: https://dev.azure.com/azure-sdk/internal/_build/results?buildId=6955780&view=logs&logId=3532

Both logs report negative branch counts. In the PR retry, compilation and ctest succeeded; coverage generation failed.

Scope

• Only coverage-enabled GNU Debug builds are affected; the existing coverage gate is unchanged.
• No SDK authentication, public API, or release-build changes.
• No coverage-file exclusions or suppression of gcovr parsing errors.
• Separate from Add STG105 Storage features #7448 and based directly on main.

Validation

• Exercised the CMake helper and confirmed it preserves existing flags and adds the atomic-update flag.
• Confirmed the coverage-disabled macro leaves compiler flags unchanged.
• Linux/GCC compilation and the affected ValidateLive Ubu2404_x64_with_unit_test coverage workload are pending CI. Verify the effective compiler flags and successful coverage generation before considering this experiment successful.

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[Copilot]

🟢 Approval recommended

The targeted flag is correctly limited by the existing GNU Debug coverage gate and preserves prior behavior.

0 open findings

What changed in this PR

Adds thread-safe GCC coverage-counter updates to reduce intermittent gcovr profile corruption.

Changes:

• Adds -fprofile-update=atomic to GNU Debug coverage builds.
• Documents why atomic counter updates are required.

File	Description
cmake-modules/​AzureCodeCoverage.cmake	Enables atomic GCC profile-counter updates for coverage instrumentation.

🧠 Review effort: Balanced

[JinmingHu (Jinming-Hu)]

/azp run cpp - storage

[azure-pipelines]

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[JinmingHu (Jinming-Hu)]

Closing as redundant: #7459 already merged the equivalent -fprofile-update=atomic coverage change into main (c236cac).