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, both paths.

   Small record arrays (data <= 131072 bytes) are expanded per element
   by `QbeGen.ArrBodyItems`/`ArrData` (predicate `HasArrayField`, not
   just nested ARRAY OF ARRAY), so each inline array field's length word
   is in the static data.  Larger ones (e.g. AST.arena, 262144 records)
   are kept compact and their element length words are set at run time
   by a generated init loop (`QbeGen.DeclRecTemplate` +
   `QbeGen.InitRecArray`, driven from `Lower`), which is what keeps the
   image inside the 4 MiB `QbeGen.sessBuf`.

   Regression: compiler/tests/t_arrrecfld.mod (small, exit 42) and
   compiler/tests/t_arrrecbig.mod (large, exit 42). *)

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.