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FPC seed drift: compiler no longer FPC-compiles (3 spots)

Symptom

fpc -O2 -Tlinux -Px86_64 compiler/compiler.pas fails, so make bootstrap (the FPC cold-start path, FPC -> pascal26 from nothing) is broken. Self-host (make compiler/pascal26, pxx builds pxx) and the committed stable_linux_amd64/.../pinned seed are unaffected — the risk only bites a from-scratch rebuild on a box with FPC and no pxx binary. Follow-on to the resolved [[bug-fpc-seed-helper-ordering-after-lua-c-frontend]] (same class, new drift).

The three drifts (pxx accepts, FPC rejects)

  1. Forward decl missing — GenMakeSeq is called (parser.inc:3529) above its body (parser.inc:7426) with no forward;. FPC single-pass: "Identifier not found GenMakeSeq". Fix: add its forward to forwards.inc (the FPC-seed forwards, included under {$ifdef FPC}).
  2. Implicit enum<->int — ir_codegen386.inc: vaTk: Integer is assigned IntToTypeKind(...) (returns TTypeKind) and compared = tyDouble. pxx erases the TTypeKind/Integer boundary; FPC keeps them distinct: "Incompatible types: got TTypeKind expected LongInt" + "Operator not overloaded: LongInt = TTypeKind". Fix: declare vaTk: TTypeKind (the value it holds).
  3. Optional semicolon — cparser.inc ~2923: an end is followed directly by if with no separating ;. pxx treats the statement separator as optional; FPC: '";" expected but "IF" found'. Fix: add the semicolon.

Note

FPC stops at the first fatal, so more drift may surface after these three — fix iteratively (fpc ... -> fix -> repeat) until it compiles, then verify make bootstrap / fpc-check: the FPC-built binary must self-host BYTE-IDENTICAL to the pxx-built one. A make fpc-check (or --require-forward pxx build for the forward-ordering subset) belongs in a periodic gate so this cannot silently re-drift.

Gate

fpc builds compiler.pas; make bootstrap green (FPC->pxx->verify byte-identical); self-host byte-identical; make test.

RESOLVED 2026-07-08 (fable-abc, Track A) — 3 fixes, fpc-check byte-identical

Exactly the 3 drifts, no further ones surfaced:

  1. forwards.inc: added function GenMakeSeq(stmt, next: Integer): Integer; forward;.
  2. ir_codegen386.inc: vaTk: Integer -> vaTk: TTypeKind (the value it holds).
  3. cparser.inc ~2923: added the missing ; after end before the if.

Gates (all green): fpc -O2 -Tlinux -Px86_64 compiler/compiler.pas builds clean; make fpc-check — the FPC-built compiler compiles compiler.pas to a binary BYTE-IDENTICAL to the self-hosted compiler/pascal26 (cmp clean); self- host byte-identical; make test. make bootstrap (FPC cold-start) works again.

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