ESP bare: try/except (raise currently terminates)

• Type: feature (backend parity)
• Track: A — compiler/exception_emit.inc, ESP backends
• Status: done
• Opened: 2026-07-03
• Found while: verifying docs/targets/esp32.md claims (Track D loop).

Problem

On --esp-profile=bare (both chips) the exception runtime is a stub: ExcSetJmp/ExcLongJmp/ExcRaise all point at EmitExit(1) — a raise parks the program instead of unwinding to a handler. Programs COMPILE cleanly, so the gap only shows at runtime. Hosted riscv32 got the real setjmp/longjmp frames on 2026-07-03; the bare profile can reuse the riscv32 machinery verbatim (nothing about it is hosted-specific — no syscalls except the unhandled message, which bare should route to UART or skip). xtensa needs its own stub set (windowed ABI needs care: register windows must be spilled before a longjmp-style sp rewind).

Acceptance

• test_cross_exception.pas boots correctly under esp_run_bare.sh on esp32c3 (riscv32 first; xtensa may split into its own ticket).
• docs/targets/esp32.md caveat updated.

Log

• 2026-07-03 — Filed by Track A. riscv32-bare = likely small (reuse hosted machinery, drop the stderr write); xtensa = larger (windowed ABI).
• 2026-07-03 — Implemented (Track A), BOTH chips (xtensa did not need its own ticket). riscv32 bare: reuse the hosted setjmp/longjmp frames verbatim (condition widened; only the unhandled-message write(2) is skipped on bare — an unhandled raise parks via EmitExit(1) as before). xtensa Call0: new stub set in exception_emit.inc (jmpbuf = a15, sp, a0 — the direct Call0 mirror of riscv32's s0/sp/ra; stub entries nop-padded to 4-byte alignment for call0) + full IR_EXC_ENTER/LEAVE/RAISE/STORE/MATCH/ MATCH_HIT/CLEAR set in the xtensa walker (EXC_FRAME_SIZE_XT=32, moving-sp frames). Windowed ABI: clean compile error (register windows would need spilling before an sp rewind); bare already rejects windowed. Verified: test/test_esp_exception.pas (except/finally/re-raise/nested) UART-matches the x86-64 oracle on esp32c3 AND esp32s3; wired into make test-esp-bare. Hosted riscv32 exception gate still green. esp32.md caveat updated.