CoreCLR: Add missing null guard

[trungnt2910]

This fixes Release builds using GCC.

Without this patch, these builds fail with:

  /home/runner/dotnet-runtime/src/coreclr/gc/unix/cgroup.cpp:518:21: error: '%s' directive argument is null [-Werror=format-overflow=]
    518 |         if (asprintf(&mem_usage_filename, "%s%s", s_memory_cgroup_path, filename) < 0)
        |             ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Part of #55803.

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[Copilot]

Pull request overview

This PR fixes a GCC Release build failure in CoreCLR’s Unix cgroup memory usage code by adding a missing null guard before formatting a path string with asprintf, avoiding a -Werror=format-overflow= warning when the cgroup path is null.

Changes:

• Add an early return in GetCGroupMemoryUsage when s_memory_cgroup_path is null to prevent passing a null %s argument to asprintf.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[janvorli]

LGTM, thank you!

[AustinWise]

The equivalent function in Mono ( getCGroupMemoryUsage ) should probably be updated to match.

[trungnt2910]

Done. I have updated the other file.

It seems like the build configuration for Mono is a bit more lenient towards warnings, so the GCC builds did not report that as an error.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.