fuzz findings [c]: undeclared disagreements (2026-08-22)

[zmaril]

Fuzzing derived programs the grammar and the reference parser disagree on.

• findings: 33 (33 undeclared)
• iterations: 5000
• we_accepted: 2432
• we_rejected: 1458
• agreed: 894
• widenings: 1538
• grammar coverage: 92.8% of alternatives

Undeclared programs the reference parser accepts but our grammar splits differently (33 distinct):

aa

; aa

; # a aa

aa aa { }

aa ( 0 ) ;

---

Filed automatically by piecework.
lang: c · kind: fuzz · grammar: 80fdf0e · corpus depth: 0 packages
ticket: fuzz-c-25880670 (exit 0)

job log tail

of 1 adjudicated)
oracle: WARNING — more files are unadjudicable than are known-valid. gap_files is a floor; read it with the indeterminate count.
oracle: verdict detail at /tmp/oracle-verdicts.json
oracle: 2 valid, 0 invalid, 1 indeterminate, 0 error (of 3 adjudicated)
oracle: verdict detail at /tmp/oracle-verdicts.json
oracle: 2 valid, 0 invalid, 0 indeterminate, 0 error (of 2 adjudicated)
oracle: verdict detail at /tmp/oracle-verdicts.json
oracle: 1 valid, 0 invalid, 0 indeterminate, 0 error (of 1 adjudicated)
oracle: verdict detail at /tmp/oracle-verdicts.json
oracle: 2 valid, 0 invalid, 0 indeterminate, 0 error (of 2 adjudicated)
oracle: verdict detail at /tmp/oracle-verdicts.json
oracle: 1 valid, 0 invalid, 0 indeterminate, 0 error (of 1 adjudicated)
oracle: verdict detail at /tmp/oracle-verdicts.json
fuzz: 2432 accepted by us (1458 discarded as unfaithful), 894 agreed, 1538 widening(s) in 33 distinct program(s) — 33 undeclared, 0 declared
fuzz: coverage — 725/781 grammar alternatives (92.8%), 166 tape(s) kept
  unreached   14  in for_statement
  unreached    7  in preproc_elifdef_in_block
  unreached    7  in preproc_ifdef_in_block
  unreached    5  in preproc_elif_in_block
  unreached    5  in preproc_if_in_block
  unreached    3  in preproc_elifdef_in_field_declaration_list
  unreached    2  in comment
  unreached    2  in preproc_elifdef_in_enumerator_list_no_comma
  476x  aa ⏎ 
   19x  ; aa ⏎ 
   29x  ; # a aa  ⏎ 
  225x  aa aa { } ⏎ 
   24x  aa ( 0 ) ; ⏎ 
  106x  aa aa aa ; ⏎ 
    1x  enum { } ; ⏎ 
  268x  aa aa { } ; ⏎ 
   98x  aa aa aa ; ; ⏎ 
    2x  asm ( L" " ) ; ⏎ 
    2x  void ; # a aa  ⏎ 
   41x  asm ( " " aa ) ; ⏎ 
    3x  asm ( L" " ) ; ; ⏎ 
    5x  void aa ( ) aa ; ⏎ 
    4x  # a undef aa  ⏎  aa ⏎ 
   19x  asm ( " " aa ) ; ; ⏎ 
    3x  void aa ( ) aa ; ; ⏎ 
    1x  # a include aa  ⏎  aa ⏎ 
    1x  struct aa { aa } ; ; ⏎ 
    1x  void [[ aa ]] auto ; ⏎ 
fuzz: report at corpus/c/reports/fuzz.json