fix(kernel): apply three upstream rxi/fe patches#20
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- fe_write() now detects and prints "..." for circular structures instead of looping forever / stack-overflowing (upstream PR #22). Relevant for the REPL where setcar/setcdr can produce circular lists. - Comment parser now terminates on \r as well as \n, fixing parse corruption with Windows-style CRLF cart source files (upstream PR #25). - fe_savegc() in fe_open() now precedes the t symbol allocation, closing a theoretical GC-during-init window (upstream PR #25). All 19 tests pass. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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PR #20 added the fe_write() cycle-detection fix (borrow GCMARKBIT, clear it in unmarkpairs) but shipped no test for it. This closes that gap. The mark bit lives in the low byte of a pair's car field, so a leaked mark corrupts the car pointer — which makes walking the structure after repr a direct, deterministic check of mark restoration (no GC needed). repr also runs fe_write twice internally (measure + fill), so a stale mark would skew the two passes. Verified the test has teeth: neutering unmarkpairs to a no-op makes the walkability checks segfault (exit 139), which ctest scores as a failure. 20/20 ctest, 23 checks in the kernel file. Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary
Applies three correctness fixes from open (but unmerged) upstream rxi/fe PRs to
kernel/fe.c. The upstream repo is effectively unmaintained — we vendor the kernel directly — so this is the right place for these.fe_write()(rxi/fe#22):fe_write()would infinite-loop / stack-overflow on any circular pair structure. Relevant now that the REPL is first-class —(setcar ...)/(setcdr ...)can trivially produce one. Fix borrowsGCMARKBITduring traversal to detect cycles, prints...in place of the back-edge, then immediately clears marks.\rcomment termination (rxi/fe#25 partial):;comment parser stopped only on\n, so a\r\n-encoded cart source file would swallow the\rinto the next token. One-character fix.fe_open()(rxi/fe#25 partial):fe_savegc()was called afterfe_symbol(ctx, "t"), leaving a window where GC during that allocation could collect the freshtobject before it was stored inctx->t. Moved the save to before the allocation.The delimiter change also in PR #25 was intentionally skipped — KEC's kernel already carries a different (extended) delimiter set.
Test plan
cmake --build build— clean compile, zero warningsctest --test-dir build --output-on-failure— 19/19 passed🤖 Generated with Claude Code