Valued defines + numeric {$IF} evaluation

• Type: feature
• Status: done
• Owner: —
• Opened: 2026-06-10 (split out of feature-mimic-fpc design)

Problem

The conditional-expression evaluator (EvalPasCondExprText, lexer.inc ~577 — shared by the lexer's ProcessPasDirective and the ExpandIncludes pre-pass, so one change point) is a pure Boolean algebra:

• Value stack PasCondValues is array of Boolean — 1 bit wide.
• Op stack PasCondOps knows (, ! (not), & (and), | (or).
• Tokenizer reads identifiers and parens only; anything else dies with conditional directive: unexpected character.
• Define tables (PasDefineNameOff/NameLen/Active) store name + flag. A define is or isn't — no value.

FPC-targeted compatibility headers evaluate, in their live branch:

{$IF defined(FPC_FULLVERSION) and (FPC_FULLVERSION >= 20400)}

That needs an integer literal (20400), comparison operators (>=), and an identifier that is True inside defined() but 30202 beside >=. The inactive-branch eval skip (440a9e0) only protects dead regions; once FPC is defined this expression is live. Hard prerequisite for feature-mimic-fpc, but independently useful (version-gated user code).

Design

1. Value lane on the define table. Parallel arrays PasDefineValue: Int64 + PasDefineHasValue: Boolean (parallel-array convention — never grow a record). v1 values come from compiler presets/mimic init only; {$DEFINE X:=value} macro syntax is deferred. ExpandIncludes snapshots define state (count/charlen/active) around each expansion — the value lane must join that snapshot or unit-local $DEFINEs leak values.
2. Tagged value stack. Slot = (kind ∈ {bool, int}, payload). Two parallel arrays: Int64 payload + kind tag. Comparisons pop two int slots, push bool; not/and/or demand bool slots. Type mixing is a loud error — 5 and TRUE dies with a message, no silent coercion.
3. Tokenizer learns two shapes. Digit run → integer literal (decimal; $hex only if a real header needs it). One-char-lookahead operators: = <> < <= > >=, each encoded as a single char on the existing op stack (e.g. =, #, l, L, g, G).
4. Identifier context rule. Bare valued identifier → int slot; bare unvalued identifier → bool via PasDefineExists (today's behavior, unchanged — zero regression surface). defined(X) unchanged.
5. Precedence. Pascal order: not > and > or > relational. Comparisons enter PasCondOpPrecedence below or. Headers parenthesize comparisons anyway (Pascal forces the habit), but match the language.

Non-goals

• Float literals (RTLVersion >= 14.2 lives only in Delphi branches, dead under mimic) — clear error if reached, never mis-evaluate.
• {$DEFINE X:=value} source syntax (defer until a header needs it).
• String comparison, arithmetic operators (+ - * div) — add only on concrete demand.

Acceptance

• Regression test/test_directive_if_numeric.pas: predefined valued symbol, {$IF X >= N} true/false both ways, defined(X) still works, <>/=/ </<=/>/>= covered, type-mix and float each produce a clear error. No mimic mode, no Synapse needed.
• Existing directive tests unchanged; make bootstrap fixedpoint holds.

Log

• 2026-06-10 — ticket opened; split from feature-mimic-fpc ("hidden structural cost" item) after walking the evaluator machinery with user.
• 2026-06-21 — done. Value lane added as parallel arrays PasDefineValue: Int64 + PasDefineHasValue: Boolean (defs.inc); PasSetDefineValue / PasDefineLookupValue helpers; PasInitDefines predefines valued PXX_VERSION = 26. ExpandIncludes snapshot (elfwriter.inc) extended to save/restore the value lane so unit-local defines do not leak values. Tagged value stack: parallel PasCondValKind (0=bool,1=int) + PasCondInt: Int64; PasCondPushBool/Int helpers. Tokenizer learns decimal integer literals (with a loud float-literal error on a trailing .) and one-char- lookahead relational ops = <> < <= > >= tagged = # l L g G. Precedence: not(4) > and(3) > or(2) > relational(1). Comparisons demand int operands; not/and/or route through PasCondSlotAsBool, which accepts a bool slot or an int that is exactly 0/1 (preserves the legacy (...) and 1 idiom) and loud-errors any other int in a boolean op (5 and TRUE). Top-level bare int is FPC-truthy. Regression test test/test_directive_if_numeric.pas (+ float and type-mix negative tests) wired into make test. Self-host byte-identical (1-gen reseed via make bootstrap); all 5 cross/ESP targets emit. No pin — directives do not change emitted code shape.