M2compiler-V3/docs/wip/arrrec-field-openarray.mod

MODULE ArrRecFieldOpenArray;
(* Repro: an array field of an array-of-record element passed as an open
   array actual.  The field's descriptor length word is never initialized
   in the static array-of-record data, so the callee reads length 0 and
   traps.  V3-built compilers miscompile this; gm2-built ones happen to
   work.  Expected: exit 0.  Actual (buggy V3): SIGABRT (134).

   Status (2026-10-08): FIXED for record arrays whose data is at most
   131072 bytes — `QbeGen.ArrBodyItems`/`ArrData` now expand record/
   class elements per element (predicate `HasArrayField`, not just
   nested ARRAY OF ARRAY) so each inline array field's length word is
   initialised.  This case used to be a single zero blob, so the field's
   count stayed 0 and the callee trapped.  Regression: compiler/tests/
   t_arrrecfld.mod (exit 42).

   Larger tables (e.g. AST.arena, 262144 records) keep the compact zero
   blob on purpose: expanding them (even interleaved `l <len>, z <n>`)
   would push the compiler image past the 4 MiB QbeGen.sessBuf.  The
   principled general fix is to initialise such counts at runtime (a
   generated init loop), not in the static data; until then the latent
   0-count bug remains for very large record arrays.  See
   docs/summary_l3_selfhost_fix.md. *)

TYPE
  ProcEnt = RECORD
    name : ARRAY [0..63] OF CHAR;
  END;
VAR
  procs   : ARRAY [0..3] OF ProcEnt;
  nProcs  : CARDINAL;
  ExitCode: INTEGER;

PROCEDURE CopyN (src: ARRAY OF CHAR; VAR dst: ARRAY OF CHAR);
  VAR i: CARDINAL;
  BEGIN
    i := 0;
    WHILE (i < 63) AND (src[i] # CHR(0)) DO dst[i] := src[i]; INC(i) END;
    dst[i] := CHR(0)
  END CopyN;

PROCEDURE NoteProc (name: ARRAY OF CHAR);
  BEGIN
    CopyN(name, procs[nProcs].name);
    INC(nProcs)
  END NoteProc;

BEGIN
  NoteProc("hello");
  IF procs[0].name[0] = "h" THEN ExitCode := 0 ELSE ExitCode := 1 END
END ArrRecFieldOpenArray.