[edsiper]

Problem

cfl_list_add_after() sets next->prev = prev instead of next->prev = _new. Forward iteration still works, but the back link of the entry after the inserted one stays on the anchor.

When the anchor is the tail, head->prev keeps pointing at the old tail. A later cfl_list_add() tail insert then links the new entry after the old tail and drops the entry that cfl_list_add_after() inserted. Reverse iteration and cfl_list_entry_last() are also wrong.

Fluent Bit hits this when restoring a removed kvlist pair after the last key, if a processor inserts at the tail afterwards. processor_labels also calls cfl_list_add_after().

Fix

Point next->prev at the inserted entry, matching cfl_list_add_before() and __cfl_list_add().

Tests

tests/list.c gets an add_after case: it inserts in the middle and after the tail, then checks the back links, a following cfl_list_add(), and forward and reverse iteration. The case fails without the fix and passes with it.

cmake -S . -B build -DCFL_TESTS=On && cmake --build build -j8
ctest --test-dir build -R cfl-test-list --output-on-failure   # fails before the fix, passes after
BUILD_DIR=build scripts/agent-verify.sh                       # 34/34 passed
valgrind --leak-check=full --error-exitcode=9 build/tests/cfl-test-list   # clean
git diff --check

Compatibility

No API or ABI change. Only the broken back link changes; callers that relied on forward iteration see the same order.