cpu_guard test: probe a libc symbol no sanitizer interposes (fixes cargo-careful on master)

[AdaWorldAPI]

cargo-careful has failed on every master merge since #355 (#355–#361; green at #354). The failing test is cpu_guard::tests::an_address_in_libc_is_not_in_the_main_executable, at cpu_guard.rs:712.

Cause. The test used malloc as its example of an address in libc. The CI job runs cargo careful … -Zcareful-sanitizer (AddressSanitizer), and ASan replaces malloc with its own interceptor linked into the executable. Under that build malloc really is in the main image, so the test's assumption is false there. The guard code is correct and unchanged.

Change. The test now uses glibc's gnu_get_libc_version instead. No sanitizer replaces it. The doc comment says why malloc was dropped.

Verified here:

• Scratch crate using the same lookup with -Zsanitizer=address: malloc in the main image is true, gnu_get_libc_version is false, and the program's own function is true. A plain build gives false / false / true.
• cargo +nightly careful test -Zcareful-sanitizer --lib cpu_guard::tests::an_address: passes. With malloc restored it fails at cpu_guard.rs:712, exactly as in CI.
• Plain build: 14/14 cpu_guard tests pass.
• The blackboard entry is in the same commit.

🤖 Generated with Claude Code

https://claude.ai/code/session_011BMJnDBAfzcuQh5HeT39Rh

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[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-13T12:29:22.209528Z	c2ec608	Draft marked ready

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