fix: detached debug symbols from guix

[PastaPastaPasta]

Issue being fixed or feature implemented

The current debug symbols shipped are not sufficient for using tools like perf

What was done?

See changes in commits; debug artifacts are now ~1.2GB per, much bigger sadly.

How Has This Been Tested?

Following process worked:

✅ Perf + Docker + External Debug Tarball: Full Symbolization Checklist

1. Extract the debug tarball

tar -xvf dashcore-*.debug.tar.gz

You should now have:
• dashd.dbg binaries
• /usr/lib/debug/.build-id/.../*.debug files

⸻

2. Find the build-id of the running dashd

sudo readelf -n /proc/$(pidof dashd)/root/usr/local/bin/dashd | grep 'Build ID'

Example output:

Build ID: 4bec1dd76cd952657cbb3e8d3b9086bdfb651904

⸻

3. Install the matching .debug file on the host

The .debug file must live at:

/usr/lib/debug/.build-id/4b/ec1dd76c...debug

So copy them:

sudo rsync -a dashcore-*/usr/lib/debug/.build-id/ /usr/lib/debug/.build-id/

⸻

4. Ensure the .debug file has the correct perf symlink

Perf expects:

/usr/lib/debug/.build-id/4b/
/usr/lib/debug/.build-id/4b/.debug

Create the symlink if needed:

sudo ln -sf
/usr/lib/debug/.build-id/4b/.debug
/usr/lib/debug/.build-id/4b/

You already did this step.

⸻

5. Copy the running binary itself to the host

Perf must see the exact same ELF that produced the build-id.

sudo mkdir -p /usr/local/bin
sudo cp /proc/$(pidof dashd)/root/usr/local/bin/dashd /usr/local/bin/dashd

⸻

6. Register the binary into perf’s build-id cache

sudo perf buildid-cache -a /usr/local/bin/dashd

⸻

7. Record + Report (dwarf mode recommended)

Record:

sudo perf record -F 99 -g --call-graph dwarf -p "$(pidof dashd)" -- sleep 30

Report with source lines:

sudo perf report --stdio -g srcline

You should now see:
• full symbol names
• file paths
• line numbers
• normal call chains

⸻

🎯 Summary

Whenever doing perf profiling inside Docker using external debug symbols:
1. Extract debug tarball
2. Find running binary’s build-id
3. Place matching .debug file under /usr/lib/debug/.build-id/
4. Create build-id symlink
5. Copy the running ELF binary to the host at the same path
6. Add binary to perf’s build-id cache
7. Run perf again — you now get full symbols

Breaking Changes

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone (for repository code-owners and collaborators only)

[github-actions]

✅ No Merge Conflicts Detected

This PR currently has no conflicts with other open PRs.

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[PastaPastaPasta]

for the first commit; --enable-debug guix builds compared to latest nightly have only 80bytes bigger shipped binary, and 64k bigger dash-qt; Negligible.

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[PastaPastaPasta]

Second commit also appears to cause no increase in shipped binaries (or minimal like 80 bytes etc)

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[coderabbitai]

Walkthrough

This pull request adds Linux-specific build-id linking and refines debug symbol handling. configure.ac appends -Wl,--build-id=sha1 for Linux targets (guarded by the existing LDFLAG_WERROR logic). contrib/devtools/split-debug.sh.in changes strip flags from -s to --strip-debug --strip-unneeded. contrib/guix/libexec/build.sh (Linux path) now compresses DWARF in .dbg files via objcopy, verifies ELF files have a Build ID and a .gnu_debuglink, builds a .build-id tree for perf discovery, and splits packaging into main and debug tarballs (excluding/including .dbg and the build-id tree accordingly).

Sequence Diagram(s)

sequenceDiagram
    participant Builder as Builder (guix build)
    participant Configure as configure.ac
    participant Linker as Linker
    participant Objcopy as objcopy
    participant FS as Filesystem
    participant Tar as Tarball packaging

    Note over Configure,Linker: Linux link-time flag selection
    Configure->>Linker: Add -Wl,--build-id=sha1 (when TARGET_OS=linux)
    Linker-->>Builder: ELF binaries with Build ID

    Builder->>Objcopy: Extract debug info -> produce .dbg
    Objcopy->>Objcopy: --strip-debug --strip-unneeded (split-debug)
    Objcopy->>Objcopy: Compress DWARF sections in .dbg
    Objcopy-->>FS: .dbg files + stripped binaries

    Builder->>Builder: Verify each ELF has Build ID and .gnu_debuglink
    alt All verified
        Builder->>FS: Create .build-id tree from .dbg files (perf discovery)
        Builder->>Tar: Package main tarball (exclude .dbg + build-id tree)
        Builder->>Tar: Package debug tarball (include .dbg + build-id tree)
    else Any missing
        Builder-->>Builder: Fail build with error
    end

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

• Files needing closer attention:
  • configure.ac — ensure correct TARGET_OS detection and interaction with LDFLAG_WERROR
  • contrib/devtools/split-debug.sh.in — verify strip flag semantics and edge cases
  • contrib/guix/libexec/build.sh — validate ELF detection, Build ID and .gnu_debuglink checks, objcopy compression options, file permissions, .build-id tree creation, and tarball include/exclude patterns (Linux-only conditionals)

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately reflects the main change: detached debug symbols are being implemented in the guix build process.
Description check	✅ Passed	The description comprehensively documents the issue, implementation approach, testing methodology, and provides detailed steps for using the new debug symbols with perf.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

contrib/guix/libexec/build.sh (1)

345-366: Minor: Silent failures in .build-id tree creation aren't caught by verification.

Lines 350–366 create the .build-id tree for perf auto-discovery. If mkdir -p or cp fail on lines 360–361, the loop continues silently. The verification phase (lines 367–396) only checks that binaries have a .gnu_debuglink section; it doesn't verify that the corresponding .debug file was successfully placed in the .build-id tree.

If the tree creation fails, perf still won't discover symbols, but the build succeeds. This is likely acceptable since the debug tarball can be extracted manually, but consider adding explicit error handling (e.g., cp ... || { echo "Error copying ..."; exit 1; }) if robustness is critical.

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 857f860 and 81cd240.

📒 Files selected for processing (1)

• contrib/guix/libexec/build.sh (2 hunks)

🧰 Additional context used

🧠 Learnings (1)

📓 Common learnings

Learnt from: kwvg
Repo: dashpay/dash PR: 6754
File: contrib/containers/guix/docker-compose.yml:18-19
Timestamp: 2025-07-14T10:11:05.011Z
Learning: In the Guix build process for Dash Core, the `guix.sigs` directory requires write access as signatures are written to it during the build process, and `dash-detached-sigs` may be updated with `git pull` operations, so both directories need rw permissions in the Docker volume mounts.

🔇 Additional comments (3)

contrib/guix/libexec/build.sh (3)

368-396: Verification block now correctly captures exit status.

The previous review flagged that the verification block ran in a subshell (due to the pipe) and the exit status wasn't properly propagated. This has been fixed: the exit status is now correctly captured via verification_status=$? after the command substitution, and the script exits with exit 1 if verification fails. Good work addressing the prior concern.

---

348-348: LGTM: Objcopy error handling is correct.

The && chaining between objcopy, mv, and chmod ensures that if any step fails, subsequent steps don't run. The previous review concern about error handling has been addressed.

---

435-446: Tarball separation logic is sound.

The main tarball (lines 436–440) correctly excludes *.dbg files and the /usr/lib/debug tree. The debug tarball (lines 442–446) correctly includes both via the find predicate \( -name "*.dbg" -o -path "${DISTNAME}/usr/lib/debug/*" \). The split is clean and deterministic.

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[UdjinM6]

utACK 81cd240

[knst]

LGTM 81cd240