[BUG] Fix conditional linking of RTCX embed dependencies & Allow null fragment names

[lamarrr]

Description

Fixes conditional compilation bug introduced in #22856.
The Zstd functions are always referenced regardless of the specified compression.
The dependency is always available regardless of the compression type, and it should be linked into the embed runner executable.
It also makes a fix to allow nullptr in fragment names.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[coderabbitai]

📝 Walkthrough

Walkthrough

cpp/librtcx/embed.cmake is updated to treat zstd as a mandatory dependency: a top-level guard terminates CMake configuration if the zstd target is absent, and the JIT runner now always links zstd and includes its headers, removing the previous conditional guard. cpp/librtcx/rtcx.cpp adds null-safety to fragment name logging by substituting "<unnamed>" when frag.name is null.

Changes

zstd mandatory dependency and logging robustness

Layer / File(s)	Summary
Top-level zstd guard and unconditional JIT runner linkage cpp/librtcx/embed.cmake	A module-level check errors out if the zstd target is not present. The JIT runner inside embed() now always links zstd and adds ZSTD_INCLUDE_DIR, replacing the prior conditional block gated on ARG_COMPRESSION.
Null-safe fragment name formatting in JIT logging cpp/librtcx/rtcx.cpp	log_nvJitLink_result now uses "<unnamed>" as a fallback when frag.name is null, preventing potential undefined behavior during string formatting of memory fragment details.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• vyasr
• mhaseeb123
• bdice

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly addresses the main changes: fixing conditional linking of RTCX embed dependencies and handling null fragment names, matching the changeset's core modifications.
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	The PR description clearly describes the changeset, referencing a previous PR and explaining both the conditional compilation bug fix and the nullptr handling improvement.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[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 `@cpp/librtcx/embed.cmake`:
- Around line 8-10: The error message in the message(FATAL_ERROR...) call within
the `if(NOT TARGET zstd)` block is misleading because it references "when
COMPRESSION is not none", but this check executes unconditionally at module load
time before ARG_COMPRESSION is set by any embed() call. Since zstd is now always
required unconditionally per this PR, update the error message to reflect that
zstd target is required unconditionally, removing the reference to the
COMPRESSION conditional logic.

🪄 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: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 97c5c6ce-73bd-4eeb-ae56-d3aa83f55d67

📥 Commits

Reviewing files that changed from the base of the PR and between b749f72 and c8f7401.

📒 Files selected for processing (1)

• cpp/librtcx/embed.cmake

[lamarrr]

/merge