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Compiler E0360: extern pointer-width ABI guard

Summary

lic rejects MIR where extern proc -> ptr (or CallExtern to such symbols) would store or return a truncated i32, via verify_mir_extern_abi before LLVM emit (E0360).

Agent continuation

  1. Read compiler/mir/mir_abi.cpp, compiler/codegen/compile.cpp (post-lower_to_mir call), li-tests/runtime/argv_ptr_abi.li.
  2. Run cmake --build build --target lic and li-tests/run_all.sh suite runtime from repo root with LI_REPO_ROOT=$PWD.
  3. Then merge stacked PR on cursor/extern-ptr-abi-guard-54aa after cursor/httpd-proxy-bench-fix-54aa; rebuild li-httpd and refresh benchmarks matrix.
  4. Blocked on human merge of proxy PR #153; no automated merge-approved on this branch.

Changed

Area Paths / evidence
MIR verify compiler/mir/mir_abi.cpp, compiler/mir/include/li/mir_abi.hpp — extern returns_i64, CallExtern/CallProc is_i64/ret_is_i64
Compile gate compiler/codegen/compile.cpp — fail build with E0360 message before emit_llvm_ir
Codegen compiler/codegen/emit.cpp — Li proc returns_i64 → LLVM i8* ret; ReturnIdent widens ptr returns
Lower compiler/mir/lower.cpp — CallExtern sets ret_is_i64; return paths tag ret_is_i64
Diagnostics compiler/diagnostics/include/li/error_codes.hpp — E0360
Tests li-tests/runtime/argv_ptr_abi.li, li-tests/manifest.toml

Not changed

  • trusted.lean / Lean VC discharge scripts.
  • std/runtime/seam.li symbol list (proxy PR).
  • Tier-5 harness oracle configs in benchmarks.
  • Typechecker rules for ptr vs int (still E0202 at type level only).

Breaking

N/A — stricter compile-time check; correct programs unchanged.

Security

N/A — prevents silent UB from ABI truncation, not a new CVE class test.

Performance

N/A — verify pass is O(MIR insns) at compile time only.

Downstream

  • benchmarks — no catalog change; consume lic builds that include this guard.
  • li-httpd — rebuild after both proxy + guard PRs land on main.