c api: enable JIT from embedded hosts; fix the macOS in-memory JIT arm

[borisbat]

Fixes #3885. The C API had no way to turn JIT on. An embedded host can now do what the CLI's -jit does: DAS_POLICY_JIT_ENABLED and DAS_POLICY_JIT_DLL_MODE join das_bool_policy, das_set_root(_n) sets the daslang root for hosts that live outside the distribution, and das_fileaccess_add_extra_module(_n) injects daslib/just_in_time.das the way -jit does. The embedding doc gains an "Enabling JIT" recipe. Script-side options jit_enabled = true stays inert: JIT is a host policy.

Testing the recipe uncovered that in-memory MCJIT execution never worked on macOS. This is the arm a static-linked host uses, and also -jit-no-cache. Mach-O codegen lowers llvm.global_dtors into __cxa_atexit(.., extern_weak @__dso_handle). RuntimeDyld cannot resolve __dso_handle in-process, and that one failed lookup silently aborts external-symbol resolution for the whole module, so every extern's GOT slot stays null and the first ctor jumps to address 0. Had resolution succeeded, the registration would fire at process exit() into the disposed engine's memory instead. The darwin in-memory arm now emits no dtor list at all; dll and exe arms are real images and keep it. CI never sees this arm on mac: the mac lane's daslang is a dll build, so its JIT sweep uses the dll-cache path. The new C test now covers it on every static ctest lane with LLVM present.

Two full-AOT (nightly-lane) fixes ride along: aot_builtin_ast.h gains the addModulePostRewriteMacro / addModulePostCompileMacro declarations that generated AOT for the ast_verify port already calls, and dasGlsl registers geom_gen.das as an AOT module lib so tests/glsl/test_geom_gen_winding.das links its geom_gen instantiations (fresh from #3886, would have reddened tonight's nightly).

Where to look: generate_global_ctors_dtors in modules/dasLLVM/daslib/llvm_jit.das (the fix and its WHY comment), src/misc/daScriptC.cpp (new surface), tests-cpp/small/test_capi_jit.cpp (the end-to-end recipe).

Validation, claims, ledger

Validation

• macOS in-memory arm (no CI lane exists for it): full tests/jit_tests swept through it, 362/362, via a temporary jit_dll_mode = false in dastest (not committed); dll arm swept green unchanged.
• dasLLVM module-owned suite on macOS: 51/51 (the changed arm is darwin-gated, so the platform matters; per its REVIEW.md no other lane covers this suite).
• Full AOT sweep (nightly-only gate): 13093/13094, 0 failed, 1 skipped, after the two AOT fixes; full JIT sweep 13921/13922; interpreter sweep 14053/14056 (3 skips). The chained preflight --full run showed suite reds that did not reproduce standalone - box contention tripping --max-file-time 30; each red gate was re-run targeted and is green.
• Negative controls (TDD audit): the C test fails when the policy switch-arm is deleted, when the extra module is inert, and when the dtor skip is reverted - the last one crashes at exit() AFTER doctest prints SUCCESS, so the exit code is the signal and ctest reads it.
• LLVM_JIT_CODEGEN_VERSION bumped 0x54 -> 0x55 per the dasLLVM checklist rule; the changed arm writes no cache artifact, so the bump costs one cold rebuild of every .jitted_scripts cache and protects nothing - kept because the rule as written demands it.

Claims - stated, not tested

• DAS_POLICY_JIT_DLL_MODE's payload is covered only by the set_bool return-code check: a static build cannot observe the field (no dll cache exists there), so a wrong-field assignment would pass the test. Verified by reading the switch arm.
• dll/exe emission is byte-identical: the skip gate is jit_mode && darwin, and jit_mode is false for dll/exe. Verified by reading the guard, plus the dll-arm probe and suite.
• On lanes without lib/LLVM.dll the JIT test case self-skips with a message; LLVM-enabled lanes (darwin26, linux, windows nightly) run it.

Not done

• The review round surfaced five REVIEW.md checklist defects (dead routing line in tests-cpp, pin-rule wording that cannot surface cross-folder edits, the codegen-version trigger being wider than the property it protects, a missing platform clause on the module-suite rule, and a proposed green-by-skip rule). All are semantic rule rewrites - queued for a ruling, not legislated here.
• A defined hidden __dso_handle dummy also fixes the resolution abort on its own (proven by IR-level bisection) but leaves the exit()-time crash; it was dropped in favor of the dtor skip, and the comment names it as the fallback if another lowering ever references __dso_handle.

🤖 Generated with Claude Code

https://claude.ai/code/session_01FkBKGJisiiHXEgSsGjpqLm

[Copilot]

Pull request overview

This PR extends daScript’s C embedding surface so hosts can enable the LLVM-backed JIT (mirroring the CLI’s -jit behavior), and fixes a macOS-specific crash in the in-memory JIT path by preventing emission of global dtors for that arm. It also includes two AOT-related build fixes needed for nightly/full-AOT lanes.

Changes:

• Add C API support for JIT enablement via new boolean policies, root override APIs, and “extra module” injection to auto-require daslib/just_in_time.das.
• Fix darwin in-memory JIT emission by skipping llvm.global_dtors generation to avoid __dso_handle/__cxa_atexit pitfalls in RuntimeDyld scenarios.
• Wire missing AOT module inputs/decls (GLSL geom_gen module stub registration; missing AOT builtin AST macro declarations).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/aot/CMakeLists.txt	Adds GLSL module-lib AOT sources to the module AOT suite list.
tests-cpp/small/test_capi_jit.cpp	New end-to-end doctest validating C API JIT enable + root round-trip.
src/misc/daScriptC.cpp	Implements new C API functions (set root, add extra module) and new policy switch cases.
modules/dasLLVM/daslib/llvm_jit.das	Skips llvm.global_dtors emission for darwin in-memory JIT arm; threads skip flag through helper.
modules/dasLLVM/daslib/llvm_jit_run.das	Bumps codegen version + emitter hash for cache invalidation / pinning.
modules/dasGlsl/CMakeLists.txt	Registers geom_gen.das as runtime-relevant AOT module input.
include/daScript/simulate/aot_builtin_ast.h	Adds missing declarations used by generated AOT for AST macros.
include/daScript/daScriptC.h	Adds new C API declarations and new das_bool_policy entries for JIT enablement.
doc/source/reference/embedding/c_api.rst	Documents the new embedding recipe (“Enabling JIT”) and new APIs/policies.

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Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

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