MVP .asm -> executable path (head #3, fast-tracked ahead of #1/#2)

• Type: feature (frontend / linker) — Track A
• Status: urgent
• Opened: 2026-06-30
• Relation: the fast, minimal slice of head #3 in [[feature-assembler-first-class-citizen]] — full design/scope is [[feature-asm-source-frontend]] (-c/ET_DYN/full directive set, stays the reference for where this grows). This ticket exists to unblock Track B sooner, not to replace that one. Consumes [[feature-asmcore-encoder-library]] (Track B, lib/asmcore, in progress — x86-64 mov reg,imm / add reg,reg / ret landed so far).

Why urgent, why now, why a cut-down scope

Track B is building lib/asmcore test-first, but today the only way to verify it is a Pascal wrapper program that calls AsmEncodeX64 directly and byte-compares (test/test_asmcore_x64.pas) — workable, but not "trivial": no way to just write a .asm fixture and run it like a normal test program.

Asking for the minimal version, not the full one. The full [[feature-asm-source-frontend]] design (object/exe/.so output, full directive set, the elegant global-symbol-resolution layer Track A wants to build properly) is bigger than what's needed right now. What unblocks Track B immediately is much smaller, and — usefully — needs zero of the label/relocation "magic" ([[feature-asm-structured-ir-library]]) at all: lib/asmcore's current instruction set (mov, add, ret) has no branches and no global references yet, so a frontend that only handles straight-line instruction sequences is sufficient today and trivially correct to scope.

Goal (cut down from the full ticket)

pxx foo.asm -> a.out (ET_EXEC only — no -c, no .so, those stay in [[feature-asm-source-frontend]]):

• Parse a flat sequence of instruction lines (mnemonic + operands, one per line, comments, blank lines) — no labels, no jmp/jcc, no extern/ global, no sections. Reject (clear error) anything needing those; they come later via the full ticket once lib/asmcore actually has branches.
• Each line becomes a TAsmInstr ([[feature-asmcore-encoder-library]]'s type), encoded via AsmEncodeX64 (or whatever target the test targets — x86-64 first, matching lib/asmcore's current coverage).
• Blit the resulting bytes into a minimal ET_EXEC via the existing elfwriter.inc writer (already supports ET_EXEC — see audit in [[feature-asm-source-frontend]]). Entry point = first instruction; program must end in ret/syscall exit or similar — whatever's simplest, this is a test harness, not a general linker yet.

Explicitly deferred to the full ticket

• Labels, branches, forward/backward jumps.
• extern/global, any cross-module symbol resolution.
• -c (object file) and --shared (.so, the confirmed ET_DYN gap).
• Multi-target — land x86-64 only for now; lib/asmcore doesn't have other targets yet either.

Acceptance

• A hand-written .asm file using only mov/add/ret (matching lib/asmcore's current coverage) assembles via pxx and runs, producing the expected result (e.g. an exit code or simple syscall side effect).
• Track B can write a .asm test fixture, run it through pxx, and check real program behavior — no more hand-deriving expected byte arrays for every new instruction lib/asmcore grows.
• Self-host byte-identical; doesn't touch anything outside this new minimal frontend path (no regressions to existing .pas/.c compilation).

Log

• 2026-06-30 — Opened urgent (Track B, on behalf of Track A scope per repo convention — touches compiler/**/elfwriter.inc). User-requested fast-track: build the minimal #3 first so Track B's own testing has a trivial path, ahead of the full 3-head sequencing in [[feature-assembler-first-class-citizen]].

DONE 2026-06-30 (self-host; FPC bootstrap deferred)

pxx foo.asm -> ET_EXEC shipped. compiler/asmfront.inc parses a flat mov/add/ret sequence (comments, blank lines; rejects labels/jumps/extern/global/ sections/syscall with a clear error), encodes each line through lib/asmcore's AsmEncodeX64 (asmcore compiled INTO the compiler via uses asmcore_base, asmcore_x64), blits the bytes into Code[] (entry = first instruction), and appends a fixed exit epilogue (mov eax,60; syscall) so the program exits with whatever it left in rdi.

• Fixture test/test_asm_mvp.asm (mov rdi,21; add rdi,rdi -> exit 42), gated by make test-asm (in make test). Track B can now drop a .asm and run it.
• PXX self-host byte-identical; full make test green; libc-free output.
• lib/asmcore reached via a built-in unit-search dir (compiler.pas AddPasUnitDir) for self-host + -Fulib/asmcore in FPCFLAGS.

Deferred (filed): FPC bootstrap can't compile asmcore (no {$mode objfpc}) — [[bug-asmcore-fpc-bootstrap]]; two name-resolution rough edges worked around — [[bug-compiler-uses-unit-interactions]]. Full directive set / labels / objects / .so stay in [[feature-asm-source-frontend]].