C: cumulative parser desync ("stray token at top level") on large multi-function files

• Type: bug. Track C (C frontend).
• Found: 2026-07-09, isolating c-testsuite 00216.

Symptom

Compiling the near-complete set of 00216's top-level functions together fails in PASS 1 (header/layout pass) with:

error: stray token at top level (not a declaration): ''

The offending token has an EMPTY SVal and is detected at EOF — i.e. the parser is off by one closing brace / one token by the end of the file. Reproduces on the PINNED v185 binary, so it PREDATES and is unrelated to the compound-literal work.

Isolation (all with 00216's globals + guv2 patched to positional)

• Each function group compiles fine ALONE: test_compound_with_relocs (local array-of-record CL), table[3]+test_multi_relocs, SEA/SEB/SEC/SED+ test_zero_init, foo.
• Every PAIR / TRIPLE tried also compiles.
• The FULL set (tcwr + sys_* + table + multi + SE + correct_filling + zero_init) desyncs by one. Not a fixed-array cap: 00216 defines only ~15 types; MAX_UCLASS=2048, MAX_UFIELD=262144, MAX_SYMS=131072, MAX_AST=524288 are far above use.

Suspicion

An accumulation bug in the two-pass driver's token accounting or in some per-decl state that is not fully reset between top-level declarations, tipping over only once enough constructs precede. Needs bisection with brace-depth / TokPos instrumentation across the pass-1 loop (cparser.inc ~6560) to find which decl leaves the cursor one token short.

Gate

The full 00216 function set parses without a stray-token desync; contributes to unskipping c-testsuite 00216 (with [[bug-c-anonymous-member-designated-init]]). [[feature-c-compound-literals]]

RESOLVED 2026-07-09 — was an unhandled form-feed whitespace char (not accumulation)

Root cause found by instrumenting clexer's "unknown punctuation" fallback: the stray empty-SVal token is a form-feed (0x0C). The C lexer's whitespace skip set was [' ', #9, #10, #13] — missing #12 (form-feed) and #11 (vertical-tab), both C6.4 whitespace. A form-feed fell through the char case to else CurTok.Kind := tkIdent (empty SVal) → surfaced as "stray token at top level: ''". 00216 has TWO form-feeds (source lines 220, 253, page-breaks between its later functions) — hence the "cumulative / only-with-all-functions" illusion (subsets excluding those lines never hit the char). NOT a cap, NOT #0, NOT unreset state. One-line fix in compiler/clexer.inc (main whitespace case + the string-continuation skips). Regression test test/cformfeed_whitespace_b220.c (form-feed between two functions → exit 42), self-host byte-identical. 00216 now stops at its remaining anonymous-member blocker ([[bug-c-anonymous-member-designated-init]]) instead of desyncing.