build-fix-diff

name	build-fix-diff
description	In a /tmp copy of a /test/<ver> source tree, iterate a candidate MariaDB fix quickly - edit the source, build a light patched binary (a single build_mdpsms_*.sh variant, default dbg), run the test, and capture the change as fix.diff via git diff. This is the /tmp fix-iteration workspace; the source copy and the patched binary both stay in /tmp (ephemeral). Use when testing or iterating a candidate fix, or when a fix.diff artifact is needed. For a durable production build in /test use qa-build; to run an existing /test build standalone in /tmp use claude-basedir-fix-copy-setup.
claude	please note - this skill exists in a public repo and should only be updated with specific written signoff by the updater. Keep skills/README.md (the skills index) in sync when any skill is added, renamed, removed, or its description changes.

build-fix-diff

A /tmp workspace for iterating a candidate MariaDB fix and capturing it as a diff. In a /tmp copy of the /test/<ver> source tree you edit the source, build a light patched binary (one build_mdpsms_*.sh variant, usually dbg), run the bug's test, and - once the fix holds - git diff the copy into fix.diff. The source copy and the patched binary both live in /tmp (ephemeral, quick to throw away and rebuild).

This is the quick fix-iteration path. It is deliberately light: one variant, in /tmp, fast to rebuild as you refine the fix. A durable, catalogued, multi-variant build is a different job.

Related skills

• For a durable production build in /test (ba/bas/bam/bat, feature/ticket renames), see qa-build instead.
• For running an existing /test build standalone in /tmp (no build), see claude-basedir-fix-copy-setup instead.
• For the full multi-version fix-verification loop, see verify-fix instead.

Inputs

• <ver> - MariaDB source-tree version under /test (e.g. 13.0, 12.3, 11.8).
• <tag> - short label for this fix (e.g. the MDEV number), used in the /tmp copy name.
• <out-dir> - where fix.diff should be written (e.g. an MDEV working dir).
• <variant> - one build_mdpsms_*.sh variant to build; default dbg.
• The source edits that close the bug (gather from conversation context), or an existing fix.diff to apply.

If not provided in the invocation, ask the user.

Procedure

1. Copy the source tree to /tmp (preserves .git/ so git diff / git apply work):

   cp -r /test/<ver> /tmp/<ver>_fix_<tag>
   

2. Apply the fix inside /tmp/<ver>_fix_<tag> - edit the affected files with the Edit tool, or apply an existing diff:

   cd /tmp/<ver>_fix_<tag>
   git apply <out-dir>/fix.diff        # only when starting from an existing diff
   

   Keep edits minimal - only what closes the bug. No cosmetic whitespace or unrelated cleanups.

3. Build the light patched binary (default dbg; one variant for speed):

   cd /tmp/<ver>_fix_<tag>
   ~/mariadb-qa/build_mdpsms_<variant>.sh
   

   The script builds in a scratch sibling (/tmp/<ver>_fix_<tag>_<variant>) and moves the finished basedir to the parent - so it lands at /tmp/<PREFIX>-mariadb-<x.y.z>-linux-x86_64-<opt|dbg>.

4. Rebake helpers on the patched binary, then run the bug's test to confirm the fix:

   cd /tmp/<PREFIX>-mariadb-<x.y.z>-linux-x86_64-<variant>
   ~/st
   cd /tmp/<PREFIX>-mariadb-<x.y.z>-linux-x86_64-<variant>    # ~/st resets cwd; cd back
   

   CLI testcase - write the SQL to in.sql, then ./anc; ./test (./anc gives a fresh datadir; client output goes to mysql.out, server log to log/master.err):

   cp <out-dir>/<testname>.sql in.sql
   ./anc; ./test
   

   MTR testcase (auto-detect test-dir - 10.6 / 10.11 use mysql-test/, 11.x+ use mariadb-test/):

   TESTDIR="mariadb-test"; [ ! -d "$TESTDIR" ] && TESTDIR="mysql-test"
   cp <out-dir>/<testname>.{test,result} "$TESTDIR/main/"
   cd "$TESTDIR" && ./mtra <testname>    # ./mtr for non-sanitiser builds
   

   Not fixed yet? Re-edit (step 2), rebuild (step 3), re-run (step 4). The /tmp build is light, so this loop is quick.

5. Capture the fix once it holds:

   cd /tmp/<ver>_fix_<tag>
   git diff > <out-dir>/fix.diff
   

6. Self-check: read <out-dir>/fix.diff and scan for hunks outside the intended scope (whitespace-only, unrelated adjacent edits). If present, undo in the /tmp copy and re-run step 5.

7. Cleanup. KEEP the /tmp/<ver>_fix_<tag> source copy (the git diff workspace) and the patched binary basedir (re-runnable) until the fix is verified; remove the build scratch:

   rm -rf /tmp/<ver>_fix_<tag>_<variant>    # build-script scratch (disposable)
   # when finished with the fix:
   cd /tmp/<PREFIX>-mariadb-<x.y.z>-linux-x86_64-<variant> && ./kill   # if a server is running
   rm -rf /tmp/<ver>_fix_<tag> /tmp/<PREFIX>-mariadb-<x.y.z>-linux-x86_64-<variant>
   

   State remaining /tmp/ dirs at end-of-turn for the user to decide retention.

Output

• <out-dir>/fix.diff - canonical git diff (with a/path / b/path and blob SHAs), the format developers expect.
• A /tmp patched binary basedir for continued standalone testing.

What NOT to include in fix.diff

• Test files (.test, .result) - those live alongside the report (see mtr_testcase), not inside the diff.
• Adjacent unrelated cleanups in the same source file.
• Cosmetic whitespace changes.

Galera builds

For a galera variant, symlink the Galera source into the copy first (/test/galera_4x; clone with /test/clone_galera.sh if absent):

cd /tmp/<ver>_fix_<tag> && ln -s /test/galera_4x .

Notes

• Edit via the /tmp source-copy, never in-place in /test/<ver> (the shared reference tree).
• Capture baselines with cp (or git show HEAD:<path>), not git stash / checkout / restore.
• cp -r preserves .git/, so git diff yields the canonical format and git apply works.
• Sanitiser builds (_san, _msan) need ./mtra for test runs, not ./mtr.
• Keep it light - one variant in /tmp. Durable multi-variant builds go through qa-build.