M2compiler-V3/docs/summary_m2s-clean.md

M2S compiles clean under V3 (compatibility additions)

Tag v3-m2s-clean. Main suite 110/110 (new t_compat).

With this, SymTab, QbeGen and M2S (the Coco/R scanner) all compile clean under V3. M2P/M2 remain (see below).

Items knocked out (the 3 remaining, plus what they uncovered)

The three known M2S items — and, once those parsed, a few more GNU-isms in CR's generated scanner tables:

1. LENGTH — accepted as an alias of LEN.
2. Empty statement bodies — IF … THEN ELSIF/ELSE, WHILE … DO, REPEAT, LOOP, FOR and CASE alternatives may now have empty bodies (StatSeq optional), matching CR's generated code.
3. & = AND, ~ = NOT — GNU/classic synonyms.
4. Octal character literals — new charConst token (0C, 03C, 012C) handled by NormLit → CHAR value (0C = NUL).
5. ORDL — alias of ORD.
6. CAP — new builtin, branchless UPCASE (q := a - 32*(a>='a' AND a<='z'), since QBE has no select).

Also fixed a latent bug found via CAP: ABS (and now CAP) wrote their result to a temp but Fact never copied it back to q, so ABS silently returned its operand. Both now CopyOp(qa, q).

Verification

• tests/t_compat.mod (exit 42) exercises &, ~, LENGTH, CAP, ORDL, 0C, and empty THEN/ELSE.
• M2S.def + M2S.mod under V3: 0 errors.
• SymTab / QbeGen under V3: still 0 errors.
• tools/m2make unaffected; main suite 110/110.

Remaining (M2P, M2)

M2P.mod (the Coco/R parser) is 107 errors, dominated by 102 undeclared identifier — within-module forward procedure calls in CR's generated recursive-descent parser (gm2 hoists these; ISO wants declaration-before-use or FORWARD). Also BITSET{…} constructors and symSet[0,0] nested-array assignment. This is the next self-hosting chunk; the driver M2.mod additionally needs nested procedure values (Error := StoreError, StoreError nested in ListHandler) which the current proc-type support doesn't yet provide (static link).

Where the compatibility additions came from

&, 0C, empty bodies and forward refs are all emitted by the CR binary's built-in scanner/parser templates — not by our scanner.frm (which has none of them). So V3 accepting them is the only way to self-host CR's output short of patching the toolchain.

Files

compiler/src/{M2.atg,QbeGen.def,QbeGen.mod}, compiler/tests/t_compat.mod, compiler/run_tests.sh.