issue: 5148137 Use tls detection flags in tls.m4 link-test

[pasis]

The TLS support link-test applied $sockperf_cv_dpcp_LDFLAGS and $sockperf_cv_dpcp_CXXFLAGS, which are never set in this macro, instead of the $sockperf_cv_tls_* variables assigned just above. With OpenSSL in a non-default prefix the detection link-test could not find -lssl, so detection failed and TLS was silently disabled
(checking for tls support... no).

Use $sockperf_cv_tls_LDFLAGS so the OpenSSL -L/-rpath derived from --with-tls= reach the link-test.

Remove CXXFLAGS usage, because it's unused in the C mode check.

Hard fail the configure stage if --with-tls requested and openssl is not found or the link test fails.

Summary by CodeRabbit

• Bug Fixes
  • Improved TLS-enabled builds by applying the correct TLS-specific compiler and linker flags during configuration.
  • Adjusted detection behavior so TLS library/header checks are handled more reliably.
  • When TLS is explicitly requested and isn’t usable, configuration now fails with a clear error instead of proceeding with a “no TLS” outcome.

[coderabbitai]

📝 Walkthrough

Walkthrough

The TLS configuration macro changes probe flag handling, applies only TLS-specific linker flags when TLS is enabled, adjusts the OpenSSL header check, and aborts configuration when explicitly requested TLS is unavailable.

Changes

TLS Build Configuration

Layer / File(s)	Summary
Wire TLS probe and build flags config/m4/tls.m4	TLS probing no longer saves CXXFLAGS; enabled TLS configuration prepends sockperf_cv_tls_LDFLAGS without the prior DPCP flag injection.
Validate TLS availability config/m4/tls.m4	The OpenSSL header check changes failure handling, and explicit TLS requests now terminate configuration when TLS is unavailable.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Poem

I’m a rabbit with TLS in my burrow,
Flags now follow the proper furrow.
Headers test, and errors speak,
Requested TLS won’t hide or sneak.
Hop, hop—configuration’s clear!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is specific and matches the main change: using TLS detection flags in the tls.m4 link test.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@config/m4/tls.m4`:
- Line 48: In TLS_CAPABILITY_SETUP, remove the CXXFLAGS assignment referencing
sockperf_cv_tls_CXXFLAGS, since the variable is not initialized and the probe
runs in C mode; retain the existing CPPFLAGS handling for the TLS include path.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Enterprise

Run ID: 925dc02a-33e2-4886-83f5-6913e9f43b1d

📥 Commits

Reviewing files that changed from the base of the PR and between 3c65ad9 and 48403cf.

📒 Files selected for processing (1)

• config/m4/tls.m4

[BasharRadya]

Consider a configure warning when --with-tls= is explicitly set but detection fails, instead of silently falling back to "no".

[pasis]

Consider a configure warning when --with-tls= is explicitly set but detection fails, instead of silently falling back to "no".

done.

[pasis]

bot:retest

[pasis]

bot:retest

[igor-ivanov]

bot:retest