Fix use-after-free and double-free in RemoveFilament

[tritsystem]

Summary

RemoveFilament() in libpromises/dbm_test_api.c frees filament (and destroys filament->items) when StringSetSize(filament->items) == 0, but had no return after that branch — every other early-exit branch in this function does.

Without it, execution falls through unconditionally to:

bool success = OpenDB(&db, filament->db_id);

a use-after-free read of the just-freed filament. At the end of the function, StringSetDestroy(filament->items) and free(filament) run again unconditionally on that same path — a double-free of both filament and its items set.

Fix is a single return; added right after the free(filament);, matching the pattern every other early-exit branch in this same function already follows.

Test plan

• Verified with a standalone AddressSanitizer repro: RemoveFilament()'s real body extracted verbatim, with minimal stub types matching the actual DBFilament/StringSet shapes. Built with -fsanitize=address, called with a filament whose items set has size 0 (the branch that frees filament).
  • Without the fix: ASan reports a genuine heap-use-after-free at the OpenDB(&db, filament->db_id) line.
  • With the fix: clean exit, no ASan report.
• Could not build/run the full libpromises test suite in this environment (no configured build toolchain for this repo here); the fix is a minimal, one-line change matching the existing early-return convention used throughout the same function, so the risk of the change itself is low.
• codespell was run against the modified file; it flagged one pre-existing, unrelated typo elsewhere in the file (fillament at line 662), not touched by this change.

🤖 Generated with Claude Code

[larsewi]

Thanks for the contribution @tritsystem

@cf-bottom Jenkins please :)

[cf-bottom]

Alright, I triggered a build:

Jenkins: https://ci.cfengine.com/job/pr-pipeline/14664/

Packages: http://buildcache.cfengine.com/packages/testing-pr/jenkins-pr-pipeline-14664/

[tritsystem]

Thanks for the quick response, @larsewi — appreciate you triggering the build. Let me know if there's anything else you'd like me to check or adjust.